Soviet Atomic Energy Vol. 47, No. 1

Body: . Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 lx Russian Original Vol. 47, No. 1, July, 1979 ic January, 1980 SATEAZ 47(1) 501-590 (1979) Ls) Filz._ SOVIET ATOMIC ENERGY ATOMHAFI 3HEP111/1 (ATOMNAYA iNERG1YA) TRANSLATED FROM RUSSIAN CONSULTANTS BUREAU, NEW YORK Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified andApproved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 SOVIET oviet Atomic energy is a cover-tbzcoyer translation of Atomnaya Energiya, a publication of the Academy of Sciences of the USSR. ATOMIC ENERGY An' agreement with the Copyright Agency of the USSR (VAAP) makes available both, advance copies of the Russian journal and original glossy photographs and artwork. This serves to decrease the necessary time lag between publication of the original and publication of the translation and helps to improve the quality of the latter. The translatiOn begin with the ,first issue of the Russian joyrnal. Editorial Board of Atompaya Energiya: Editor: 0. D. Kazachkovskii Associate Editors: N. A. Vlasov and N. N. Ponomarev-Stepnoi Secretary: A. I. Artemov ? I. N. Golovin ' V. V., Matveev V. I. ll'ichey I. D. Morokhov V. E. Ivanov A: A. Naumov V. F. Kalinin A. S. Nikiforov P. L. Kirilloy ' A. S. Shtan' Yu. 1. Koryakin B. A. Sidorenko A. K. Krasin M. F. Troyanov E. V. Kulov? E. I. Vorob'ev B. N. Laskorin Soviet Atomic Energy is abstracted or in- dexed in Chemical Abstracts, -Chemical Titles, Pollution Abstracts, Science Re- search Abstracts, Parts A and B, ,Safety Science Abstracts Journal, Current- Con- tents, Energy Research Abstracts, and Engineering Index. Copyright C) 1980, Plenum' Publishing Corporation. Soviet Atomic Energy partici- pates in the program of Copyright Clearance Center, Inc. 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Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 SOVIET ATOMIC ENERGY A translation of Atomnaya Energiya January, 1980 Volume 47, Number 1 July, 1979 CONTENTS ARTICLES Combination of Nuclear-Geophysical Methods and Apparatus for Increasing the Efficiency of Prospecting, Extraction, and Reprocessing of Nonradiactive Mineral Raw Materials (by the Example of Tin Ores) - S. A. Baldin, S. N. Voloshchuk, B. G. Egiazarov, L. V. Zernov, I. A. Luchin, V. V. Matveev, L. Ch. Pukhal'skii, Engl./Russ. and N. I. Chesnokov 501 3 Algorithm for the Extremal Control of the Energy Distribution in a Power Reactor -1. Ya. Emeltyanov, V. V. Postnikov, and G. V. Yurkin 506 8 Some Peculiarities of the Structure of the Flow in the Case of Critical Discharge Conditions of Boiling Water through Cylindrical Channels - V. S. Aleshin 512 12 Dependence of the Ejection Coefficient of Uranium on the Flux of Thermal Neutrons -G. P. Ivanov, V. A. Bessonov, N. A. Grinevich, V. A. Popovichev, and E. A. Borisov 516 15 Effect of Irradiation on The Ultimate Fracture Strength of the Alloy Zr-2.5% Nb - 0.A.Shat-skaya, E. Yu. Rivkin, A. M. Vasnin, V. V. Klyushin, A. V. Kozlov, V. M. Nalesnik, and M. E. Rodin 519 18 Role of Impurities in Irradiation Embrittlement of Low-Alloy Steel - V. A. Nikolaev, V. V. Rybin, and V. I. Badanin 523 21 Yields of Some Fragments from Fission of 235U, 238u, and 239Pu by Neutrons from Spectrum of BR-1 Fast Reactor - L. N. Yurova, A. V. Bushuev, V. N. Ozerkov, V. V. Chachin, A. V. Zvonarev, Yu. G. Liforov, Yu. V. Koleganov, V. V. Miller, and 0. V. Gorbatyuk 528 26 Neutron Yield of (a, n) Reaction onOxygen -V. I. Bulanenko 531 28 Instrumental Neutron-Activation Analysis of Submilligram Amounts of Geochemical Samples - V. I. Drynkin, E. V. Karns, V. D. Nartikoev, B. V. Belen'kii, and A. L. Kerzin 534 31 Calculation of Photoneutron Yields from Thick Targets in Giant-Resonance Region -V. I. Isaev and V. P. Kovalev 538 34 LETTERS TO THE EDITOR An Accelerating Section for Reducing the Radiation Level in the Absorber Section of a Linac - V. S. Balagura, V. M. Grizhko, I. A. Grishaev, L. K. Myakushko, B. G. Safronov, and G. L. Fursov 543 39 y-Ray Recording Efficiency of a Spherical Detector - D. I. Konstantinov 546 41 Examination of Irradiated Metal Diborides by X-Ray Diffraction - Kh. Maile, I. A. Naskidashvili, and T. Sh. Berdzenishvili 548 42 Neutron Spectra in the MeV Range in Fast Critical Assemblies - V. M. Lityaev, V. A. Dulin, and Yu. A. Kazanskii 550? 44 Effects of Various Factors on the Absorbed-Dose Distribution in Thin Layers -V. V. Krayushkin 552 46 A Calorimeter for Measuring Local Electron-Beam Absorbed Doses - V. A. Berlyand, V. V. Generalova, and M. N. Gurskii 554 47 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Determination of Nuclear Constants as an Inverse Problem in Radiation Transport -V. N. Dushin CONTENTS (continued) Engl./Russ. 556 48 Effects of Bombardment by He+, Ni+, and Cr+ on Microhardness and Corrosion Cracking of Stainless Steels - B. G. Vladimirov, V. M. Gusev, and V. S. Tsyplenkov 558 50 Nonstationary Prompt-Neutron Diffusion in a Fast Assembly - V. E. Kolesov, 0. I. Makarov, and I. P. Matveenko 560 51 Effects of Ion-Bombardment Dose and Previous Surface Treatment on the Erosion of Molybdenum - B. A. Kadin, D. M. Skorov, and V. L. Yakushin 562 53 A Cadmium-Sulfide y-Ray Dosimeter with Elevated Stability under Irradiation -V. K. Dubovoi 564 54 The Thermal-Neutron Fission Cross Section and the Fission-Resonance Integral for 243Cm - K. D. Zhuravlev and N. I. Kroshkin 565 55 Absolute Measurement of the Branching Ratio for the 277.6-keV Line of 239Np -V. K. Mozhaev, V. A. Dulin, and Yu. A. Kazanskii 566 55 Calculation of the True Volume Proportion of Steam in the Driving Section of a Natural- Circulation Loop - L. N. Polyanin and A. L. Putov 567 56 A Local Approach to Determination of the Coordinates of an Interface - F. L. Gerchikov and V. D. Kosarev 569 57 ANNIVERSARIES Academician Pavel Alekseevich Cherenkov (On His 75th Birthday Anniversary) - E. I. Tamm and B. B. Govorkov 572 59 The 50th Birthday Anniversary of Evgenii Vladimirovich Kulov 574 60 INFORMATION The Accident at the Three Mile Island Nuclear Power Plant 575 61 CONFERENCES, MEETINGS, AND SEMINARS Second All-Union Conference on the Chemistry of Uranium - g. A. Semenova 579 63 Symposium on the Scientific Foundations of Radioactive Waste Handling - V. I. Spitsyn and A. S. Polyakov 580 64 Conference of Experts on the Effect of Nuclear Power on the Environment - L. A. Win and V. I. Karpov 582 65 Scientific-Technical Conference "Energy and Environmental Protection" -B. M. Stolyarov 583 66 International Seminar on the Practical Significance of the ICRP Recommendations -Yu. V. Sivintsev 585 67 Conference on the Disruptive Instability in Closed Systems - V. G. Merezhkin 586 ' 68 NEW BOOKS V. L. Blinkin and V. M. Novikov. Liquid-Salt Nuclear Reactors - Reviewed by Yu. I. Koryakin 588 69 V. V. Fisenko. Critical Two-Phase Flows -Reviewed by V. N. Sxnolin 588 69 Tritium Measurement Techniques - B. P. Maksimenko 590 70 The Russian press date (podpisano k pechati) of this issue was 6/27/1979. Publication therefore did not occur prior to this date, but must be assumed to have taken place reasonably soon thereafter. Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 ARTICLES COMBINATION OF NUCLEAR-GEOPHYSICAL METHODS AND APPARATUS FOR INCREASING THE EFFICIENCY OF PROSPECTING, EXTRACTION, AND REPROCESSING OF NONRADIOACTIVE MINERAL RAW MATERIALS (BY THE EXAMPLE OF TIN ORES) S. A. Baldin, S. N. Voloshchuk, V. G. Egiazarov, L. V. Zernov, I. A. Luchin, V. V. Matveev, L. Ch. Pukhal'skii, and N. I. Chesnokov UDC 550.835.08 A promising trend for the utilization of ionizing radiations in the national economy is the development of nuclear-physical methods and apparatus for solving the urgent problems of increasing the efficiency of prospecting, extraction, and reprocessing of mineral raw materials. The greatest successes in this field have been achieved with the high-speed analysis of uranium ores by a radiometric method, based on record- ing the natural y radiation with reference to a simple apparatus [1]. When solving similar problems for non- radioactive raw materials, use is made of the stimulated radiation induced in the substance by means of iso- tope sources, particle accelerators of various types, nuclear reactors, etc. One of the most effective methods of analysis of a substance in applied problems is the roentgenoradio- metric method (RRM), consisting in the excitation in the substance of x-ray characteristic emission with radioisotope sources and its subsequent recording by means of spectrometric equipment. The energy spectrum of the induced radiation contains, together with the x-ray characteristic emission of the required element, the characteristic emission of other elements occurring in the composition of the ore, and also primary scattered radiation. Because of this, the necessary sensitivity and high measurement speed in the majority of cases can be attained only by using spectrometric instruments which are relatively complex in structure and composition, with devices for the automatic processing of the measurement results. This makes the use of nuclear-physics methods extremely difficult for the complex analysis of nonradioactive ores under production conditions, although several important problems at the present time have been success- fully solved by these methods. Nuclear-geophysical methods of logging, sampling uncrushed core samples and ores in the natural de- posit, analysis of powdered samples, etc. have been developed and introduced, and in a number of cases methods for monitoring sorted ore, concentration products, pulps and solutions are being used. At the same time, automated methods and equipment for high-speed analysis and preliminary sorting in transportable tanks, separation into finely divided batches and lumps have almost been uninvestigated and unused, although on individual problems there are publications indicating the formulation of the problem, the results of labora- tory investigations and certain positive experiments [2, 4]. In this present paper, the results of the development and introduction of a combination of nuclear-physi- cal methods and equipment are recounted, which provide an effective solution for the production problems at all the principal stages of monitoring the mining-metallurgical production of tin. Taking into consideration the nuclear-physical characteristics of tin and the requirements for production, roentgenoradiometric [3] and y-resonance methods of analysis [5] have been accepted mainly for the analytical monitoring of the complex. The latter is used in those cases when it is necessary to monitor the tin in the form of cassiterite or to carry out phase analysis on compounds of tin and iron. Depending on the production problems to be solved, semiconductor detectors (SCD), scintillation and proportional counters are used, and also isotope sources of 241AM, 147pm, and 119MSn. The constitution of the equipment complex developed for monitoring in the different stages of the mining-metallurgical production process is shown in Fig. 1. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 3-7, July, 1979. Original article submitted January 30, 1979. 0038-531X/79/4701-0501$07.50 1980 Plenum Publishing Corporation 501 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 TABLE 1. Averaged Indices of Lump Separation Techno- logical sample Total mass. tons Coarseness grade, mm Average yield of grade,% Av. tin content (chem. Tailings Concentrate Conc. factor, rel. yield from yield from orig. tin content, yield from yield fromorig tin content, anal. ),0/0 grade,% ore,010 010 grade. 010 ore,u/c, 010 units 1 69,6 63-100, 13,6 0,138 51,0 6,8 0,071 50,0 6,8 0,185 1,45 100-203 17,4 0,176. 44,0 . 7,7 0,060 56,0 9,7 0,267 1,52 2 48,0 63-100, 14,4. 0,096 85,0 12,2 0,055 15,0 2,2 0,328 3,4 100-200 18,0 0,130' 79,0 14,2 0,072 21,0 3,8 0,348 2,7 3 7,74 20-32, 8,5 0,174 63,0 5,4 0,100 37,0 3,1 0,3)1 1,72 32-63 15,6 0,220 81,0 12,6, 0,070 19,0 . 3,0 .0,860 3,9 Fig. 1. Structure of the complex and monitoring functions: A) monitoring for prospecting, extraction, and sorting processes; B) control for treatment processes; 1) sampling; 2, 3) logging of shot holes and bores; 4) high-speed analysis at the ore-monitoring station; 5) sorting; 6) surface logging; 7) laboratory analysis of samples, core, and ores; 8, 9) batch. and lump separation; 10) high-speed analysis of products; 11) tailings; 12) laboratory anal- ' ysis of samples; 13, 14) continuous monitoring for metallurgy (solution monitoring) and concentration (pulp monitoring) processes, respectively. In search and prospecting, the results of the roentgenoradiometric ore sampling at the site of the seam and of the uncrushed core sample, logging of the drillholes, roentgenoradiometric and y-resonance analysis of the powdered samples (see Fig. 1: 1, 6, and 7) are used for the selection of promising sections and for ob- taining the initial data for calculating the reserves. At the stage of extraction and preliminary concentration of ores, by means of roentgenoradiometric ore sampling at the site of the seam and the uncrushed core sample, logging of shot holes and drillholes, high- speed analysis and sorting of the ores into transportable containers, preliminary concentration of the ores into finely divided batches and lumps, and analysis of the powdered samples by roentgenoradiometric and 'y-reso- nance methods (see Fig. 1: 1-3, 6-9) are obtained starting data for calculating the reserves for detailed and operational prospecting, and optimization of the extraction process; prerequisites are established for the se- lective extraction and abandoning of substandard ores in the form of untouched blocks and rubbish, in order to reduce losses and depletion, and the extraction of the part of the shattered rock massif which is substan- dard in the content of tin. In order to monitor and control the ore treatment process, the results of the roentgenoradiometric sam- pling of the ore on a conveyor belt are used, as are monitoring of the tin content in the solid phase of pulp and solu- tions in a continuous cycle, roentgenoradiometric and 'y-resonance analysis of samples for tin and its accom- panying components (see Fig. 1: 10, 12-14). The data obtained from the measurements allows the content of tin and accompanying elements to be determined in the ores and in the products of their treatment. 502 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Fig. 2 Fig. 3 Fig. 2. Irradiation and detection unit, with a semiconductor detector, at the ore- monitoring station. Fig. 3. Irradiation and detection unit of a facility for the separation of ores with a semiconductor detector. In the mining instruments for logging, sampling of the uncrushed core sample and ore at the site of the seam, scintillation detection units are used, with a thin sodium iodide crystal. The sensitivity threshold in the case of roentgenoradiometric sampling amounted to 0.05%, and in the case of logging - 0.07%. By compar- ing the results of the roentgenoradiometric sampling with the conventional furrow sampling, the mean-square error in determining the content of tin amounted to from *32 (for agradecontaininglesethan0.1%) to *13% (for a grade containing more than 0.5%). ? The relative mean-square error in the data from a comparison of logging with laboratory analyses of core samples is equal to ?30% for a grade containing less than 0.1%. It should be noted that the error of conventional geological sampling is *40-60%. The sampling output amounts to not less than 20 m per shift, and the logging output is not less than 100 m per shift on the instrument. At the present time, using RRM, more than 30 km of the walls of mine workings can be sampled, and more than 10 km of drillholes bored from underground mine Workings is logged. In the facilities for high-speed analysis, sorting and separation of ores into transportable containers, finely divided batches and lumps, detection units are used with silicon semiconductor detectors (area of sensi- tive surface -,250 mm2). The time for the roentgenoradiometric analysis of a single truck is 15-20 sec, and the output is more than 300 trucks per shift. More than 300,000 trucks have been analyzed in a production cycle on this facility. The cost of the high-speed analysis of the ore mase in the truck by the roentgenoradio- metric method is szi3 times less than the cost of handful sampling with a sharp increase of the measurement output, providing automation of sorting. An irradiation unit and a detection facility with a cooled semiconductor detector and 4 isotope sources of 241Am in shielded equipments with collimators is shown in Fig. 2. Investigations conducted on the facility for separation into finely divided batches and lumps under produc- tion conditions have shown the feasibility in principle and technically of roentgenoradiometric concentration. It has been established that the content of tin in the lumps or batches is determined with an error of 30-40%, which is sufficient for the efficient separation of ores according to content, and the analytical sensitivity allows sorting to be carried out under batch and lump conditions with an output of 5-15 ton/b or more, depending on the coarseness of sorting of the material (Table 1). The measurement section of the facility for ore separation is shown in Fig. 3, in which can be seen the lower part of the detection unit with the semiconductor detector and 4 isotope sources, positioned in pairs on 503 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Cse,% 4 100 8 6 4 2 2 4 6 8 101 4 6 8 100 RRM, Sn % Fig. 4. Comparison of results of high-speed analysis of tin ores in trucks (roentgenoradiometric method) and bulk sampling (Csn, chemical analysis); ?) skarn ores; 0) shales. 2 ? . both sides of the detector. Both facilities for the preliminaryroentgenoradiometric concentration operate-_. in the automatic regime and are equipped with processor-analyzers for processing the databy a specified al- gorithin and also monitoring and control devices with external slave mechanisms. It should'be noted that facilities for the contactless automatic sorting and separation of ores; based on RRM, have been constructed and tried out under industrial conditions for the first time. - . Roentgenoradiometric and x-ray absorption instruments and facilities for the Continuous monitoring of ' concentration products (pulps and solutions) are based on the application Of saint-illation and semiconductor detector units. The sensitivity threshold for the analysis of pulps and solutions with a Semiconductor detector is 0.001-0.003 wt.% and 5-10 mg/liter, respectively, and foraoluticins with scintillatiOn detectors it is 70 mg/ liter. The instruments and facilities provide data extraction into external equipments (digital printout, pen recorder) and to the production process monitoring and control system.. The laboratory instruments developed for the analysis of powdered bre samples and their treated prod- ucts include 'instruments for determining the content of the total tin and tin oxide (in the form of tassiterite) by roentgenoradiometric and y-resonance methods, instrtunents based on semiconductor spectrometers for determining the content of tin and accompanying elements by the roentgenoradiometric method, and instru- ments for the phase analysis of tin and iron in ores and processed products by the y-resonance method. The accuracy of the analyses of powdered samples is not inferior to, and in some cases even exceeds, the accuracy of chemical analysis. The sensitivity threshold is 0.005-0.02% of the total tin and tin in the form of cassiterite. The mean-squire relative deviations of the results of analysis by the y=resonance method of the tin con- tent in the form of cassiterite from the results of chemical analysis are given below: 504 Grade of tin No. of deter- ?Deviation ,% content,% minations 0.05 454 ? ?58.4 0.05-0.1 405 ? 27.3 0.1-0.25 447 ? 16.2 0.2571 229 ?11.2 1 ? 88 ?5.2 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 TABLE 2. Distribution of a Mined-Ore Mass According to Range of Content of Tin, Based on High-Speed Analysis of Ores in Trucks by the Roentgenoradiometric Method, % Range of tin content Average I content Yield of I ore Yield of I tin Range of tin content Average I content lYield of I ore Yield of I tin 0-0,10 0,04 33,5 7,6 0,30--0,40 0,34 8,8 17,0 0,10-0,15 0,12 18,3 12,9 0,40-0,60 0,51 6,8 19,7 0,15--0,30 0,21 37,4 39,3 0,60 0,89 0,9 4,5 The results of comparisons for other types of analyses of powdered samples on tin and incidental com- ponents also have shown the high accuracy and sensitivity of roentgenoradiometric analyses. In all, ??=1 300,000 samples have been analyzed. The output of the analyses is 100-120 analyses per instrument per shift. It is well known that the roentgenoradiometric method has a low penetration depth, not exceeding a few millimeters, because of which the most important problem of the investigations was to estimate the represen- tability and accuracy of the results of the analyses in the case of logging, sampling at the site of the deposit, and especially in the high-speed analyses in the transportable containers. Comparison of the results of the determination of the tin in a surface seam of ore loaded into a truck by the roentgenoradiometric method and by total sampling with chemical analysis of selected samples (> 500 trucks with different tin contents) showed that there is a direct correlation dependence between them. For a tin content of < 0.1 and > 0.1%, the corre- lation coefficient amounted to 0.71 and 0.82 with a relative mean-square error for both content grades of k's ?30% (Fig. 4). Similar data were obtained when comparing the results on representative bulk investigations of roentgenoradiometric sampling at the site of the deposit and logging with furrow sampling and sampling of drillhole core samples by conventional methods. Thus, according to the content of tin determined by the roentgenoradiometric method in a surface seam, the tin content in the volume investigated can be judged quite accurately, which confirms the calculations by the Materon?de Wies formula, and which showed the feasibility of replacing bulk elements with linear or area equivalents of these samples with preservation of the statis- tical representation of sampling [6]. The application of the combination of nuclear-geophysical methods and equipment provides an important economic effect, due to the replacement of conventional methods of analysis and sampling by nuclear-geo- physical methods and the change of technology of prospecting, extraction and processing of tin ores. Thus, the cost of the nuclear-geophysical analysis of powdered samples is a factor of 6-8 less than that of chemical analysis, and the cost of nuclear-geophysical sampling at the site of the deposit is a factor of 5-6 less than furrow sampling, etc. Already at the present time the effect of using the instruments of the complex in pro- duction has amounted to about 1 million rubles. The use of logging of drillholes and shot holes and sampling at the site of the deposit allows the greater part of drilling with sampling of the core to be replaced by more productive and cheaper coreless drilling, the volume of the shattered rock mass to be reduced because of the part of the substandard ores remaining in the depths in the form of untouched blocks, and prerequisites to be created for selective extraction and reduction of depletion and losses. The introduction into the technology of extraction, of high-speed analysis and sorting of ores in transport containers, preliminary concentration into finely divided batches and lumps will allow 20-40% of the waste tailings with a tin content of 0.06-0.08% to be separated, which will make it possible to reduce the volume and to increase the content of tin in the ore directed to further processing by a factor of 1.2-1.5. For example, during the development of one of the experimental units, using nuclear- geophysical methods, 5.6% of the ore with a tin content of ?0.08% remained in the depths in the form of un- touched blocks; according to the data of high-speed analysis of the ores in trucks with a limiting content of 0.1%, 33% of the tailings was separated with a tin content of 0.04%; the concentration factor in this case amounted to 1.37 (Table 2); and with a limiting content of 0.15%, 51.8% of the tailings was separated with a tin content of 0.07% and a concentration factor of 1.61. The preliminary concentration of ores into finely divided batches and lumps allows the tin content in ore directed to further processing to be increased additionally, and its volume to be reduced. As investigations have shown, in the case of lump sorting of ores with a size of 32-200 mm by the roentgenoradiometric method, 505 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 15-25% of the tailings (from the original ore sent for concentration) is separated with a tin content of 0.05- 0.08%. Technicoeconomic calculations and the results of industrial operation of a complex show that the to- tal effect of its introduction amounts to 2-3 rubles per ton of ore. Conclusions. A combination of nuclear-geophysical methods and equipment has been developed, tested, and introduced into commercial operation, for searching, prospecting, extracting, and processing lean tin ores, encompassing the whole production cycle. The introduction of the complex significantly increases the technicoeconomical production indices as a whole, allows the use of a more productive extraction technology, ore processing, and the creation of automated production control systems. The use, inthe complex, of equip- ment with semiconductor detectors in conjunction with analyzer-processors has allowed for the first time in the practice of the mining and concentration industry the creation ,of automatic roentgenoradiometric facilities for contactless high-speed analysis, sorting and preliminary concentration of lean tin ores into transport con- tainers, finely divided batches and lumps. The design of the complex, the flow-sheet?technological principles of equipment construction and the methods of measurement provide the capability for using it to solve similar problems for other types of nonradioactive raw materials, such as molybdenum, tungsten, zinc, copper, and other ores, including complex ores. LITERATURE CITED 1. L. Ch. Pukhaliskii and M. V. Shumilin, Prospecting and Sampling of Uranium Deposits [in Russian], Nedra, Moscow (1977). 2. A. P. Ochkur et al., Gamma Methods in Ore Geology [in Russian], Nedra, Leningrad (1976). 3. E. P. Leman et al., Nuclear Geophysics in Ore Geology [in Russian], NPO Geofizika, Leningrad (1977). 4. A. P. Tatarnikov, Nuclear-Physics Methods of Concentration of Minerals [in Russian], Atomizdat, Moscow (1974). 5. V. I. Gol'danskii et al., Gamma-Resonance Methods and Instruments for Phase Analysis of Mineral Raw Materials [in Russian], Atomizdat, Moscow (1974). 6. E. Karl'e, Procedure for the Quantitative Assessment of Uranium Deposits [in Russian], Atomizdat, Moscow (1961). ALGORITHM FOR THE EXTREMAL CONTROL OF THE ENERGY DISTRIBUTION IN A POWER REACTOR I. Ya. Emeliyanov, V. V. Postnikov, UDC 621.039.562 and G. V. Yurkin It is necessary in the development and operation of large-capacity power reactors to equip them with automatic systems for the control of the energy distribution (ED) in the active zone which are based on digital computers. For the extremal control of the ED, i.e., for the control of the ED with a search for the optimal values of a goal function, programs were used which are based on implementation of different "classical" optimiza- tion schemes [1-3]: Wiener's theory, dynamic programming, the maximum principle of Pontryagin, and others. However, these methods are complicated with respect to instrumentation (they require a large mem- ory and a lot of computer time), they are calculated for a single extremum determination, and in addition they can lead to errors due to inadequacy of the process in the reactor and the model of it used in the control algorithms [11. Thus, e.g., in order to calculate a single control cycle in experiments on an HBWR, 5min of computer time, 7K of operator memory, and 240K of disk memory (K represents 1024 machine words) are necessary. The difference between the actual process and a linear model of it was eliminated by the introduction of a large number of artificial variables [2]. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 8-12, July, 1979. Original article submitted February 2, 1978. 506 0038-531X/79/4701-0506$07.50 01980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Deformation of the ED, % 0 1 -2 - 2 :b), /h _ 3 15 -4 - 4 .= -5 tt -6 - -6 .8 7 mz -8 - .g 8 t-.1 1,50 -10 - 1,46 -12- -14 - -16 - i 1,38 -18 - 7,34 -20 I i I I I 1,30 50 100 150 Time, sec 4% 22,25 21,95 21,65 21,35 21,05 i I I J I 20,75 40 44 0 4 8 12 16 20 24 28 32 36 Iterations Fig. 1 Fig. 2 Fig. 1. Deformation of the ED in the 30-56 cell (-) at constant average power of the RBMK-1000 reactor of the LAgS, and the position of the CR in the 24-57 cell (---). Fig. 2. Dependence of Kr (0) and a (0) on the number of iterations of CR control (p(k) =4). The solution of the problem with the application of a reactor model improved by the method of dynamic programming [3] required an operator memory of -40,000 words, 130,000 words on a magnetic drum, and -500 sec of computer time (on a computer of the HITAC 5020E type); in the opinion of the authors, 104 times more machine time would be required for the usual method of dynamic programming [3]. Therefore, the question of choosing the most acceptable method of controlling the ED has not been conclusively resolved. On the one hand practical testing and a sufficient number of experiments are necessary to accomplish this, and on the other hand a comparison of the different methods in a specific class of problems is necessary. The most important characteristics of the algorithms are their complexity, the convergence rate, sta- bilityto noise, computation time, and so on. The difficulties of implementing general optimization schemes associated with the processing of information of large volume and dimensionality have led to the appearance of a different kind of iterative heuristic procedures based on a step-by-step (pulse) search for the optimum and capable of finding the extremum of a goal function with simultaneous refinement of the algorithm param- eters [4]. The heuristic side of step-by-step search methods has been investigated in [5]; however, it has seldom been discussed with application to the problems of the optimal control of the ED. It is advisable in this connection to discuss the extremal control of the ED with the help of a step-by-step search of the extremum with a combination of test and working steps and in combination with a number of heu- ristic methods of self-adjustment of the parameters. Heuristic and logical methods of self-adjustment, which recall the procedure implementable by an operator behind a control panel, minimize the machine time costs for solution of the problem. STATEMENT OF THE PROBLEM AND A DESCRIPTION OF AN ALGORITHM FOR ITS SOLUTION The problem of extremal control as a method of automatic optimization [6] consists of the minimization or maximization of some goal function whose value depends on controllable and uncontrollable parameters of an object. One can select as the goal function the nonuniformity coefficient of the ED with respect to the reactor radius: Kr = max [IV (r, P)/SW0 (r)1; S W (r, p) du S ? W r) dv Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 (1) 507 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 where W(r, p) is the actual ED, which depends on the position of the control rods (CR), and Wo(r) is the spec- ified ED. Each component of the vector p is of the form P./ = TIP1j7 (2) (3) and 0 a C. At the same time n(k) and nit Ix satisfy the relationships nun (4) (4) (OM int nmax?nmin-- ? ctC / ' ?ax (k) (4) 13(k) nm+nmin=n ='T-c 1< p( ' ray incident on the detector near point A at an angle 0 to the interior normal is 2R cos 0; the probability that the y ray will interact with the detector material is 5E, ft= 1 ?exp (-2?0R cos 0), where tio is the linear attenuation coefficient for y rays in the material of the detector. We integrate LE ,R with respect to a to get the number of y rays recorded by the detector in unit time that enter the detector near A; 1 dl% r rec= (on dS/4p ) ?(a?1 dS/2p) [ (2410R)2 (1 -I- 210R)/(2P0R)2 exP(-2poR)] We integrate (2) over the surface of the detector and divide the result by Ntot to get the efficiency for y-ray detection for a homogeneous isotropic medium containing uniformly distributed activity: (2) e = (Nrec/Ntot )= I ? (1/2 (LoR)2) ?[(1+2PoR)/2 poR)21 exp (-211/4R). (3) Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 41-42, July, 1979. Original article submitted November 2, 1977. 546 0038-531X/79/4701-0546$07.50 CI 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 dv Fig. 1 Fig. 2 Fig. 1. A spherical detector recording y rays in a homogeneous isotropic medium containing uniformly distributed activity. Fig. 2. Recording of y rays from a planar source with a spherical detector. This expression differs from the corresponding formula of [4], and the difference is due to the inexplicit assumption in the latter study that the angle of distribution of the radiation at the surface of the detector is isotropic, which our argument shows to be incorrect. We now consider the efficiency of this detector for y rays from a planar source having any angular distribution for the radiation, which is however the same for any point on the source. Clearly, such a source can be represented as the superposition of planar unidirectional sources. In many practical instances one can neglect the attenuation of the radiation in the medium between the source and the detector, and then the spheri- cal form of the detector makes the efficiency the same as that for any of the unidirectional sources constitut- ing the planar source. It is therefore sufficient to consider the radiation from a planar unidirectional source. The efficiency of a y-ray detector in an isotropic medium containing uniformly distributed activity can also be derived from the efficiency in the field of a planar unidirectional source [2]. We introduce a cylindrical coordinate system with its origin at the center of the detector and with its z axis parallel to the radiation direction of the unidirectional source (Fig. 2). The total number of y rays pas- sing through the surface of the detector in unit time is = aroaini (e)/cos 01, where 0 is the angle between the z axis and the normal to the plane of the source, al is the specific activity, and ni is the quantum yield. The thickness of the detector m1(p, R) in the direction of arrival of a y ray at a distance p from the z axis is 2, 1/72-7. Then the y-ray detection efficiency is R e (N reSI t'ot )= (1/nR2) S [i?exp ( ? 2?0 -1/ R2 ?p2)1 p dp o o 1 ? 1-F2NR =--- 1 2?0R), 2 (?0R)2 2 (p0R)2 exp ( which agrees with (3), as would be expected. The error in [2] is due to an error in, calculating the integral in (4) (4) Numerical integration has been used [3] to determine the efficiency for such a detector in the y-ray field set up by a planar source with a cosine distribution and arbitrary dimensions. The values for the efficiency given in [3] for an infinite source agree with those from (3) within the error of the numerical integration. This efficiency formula can be used in sensitivity calculations for radiometers, as well as in determin- ing the photoelectric efficiency and the activity of bulk-distributed sources. lam indebted to Professor V. V. Matveev for valuable comments. LITERATURE CITED 1. C. Sybesma, Measurements of Continuous Energy Distribution y Rays in a Scattering Medium, Amster- dam (1961). 2. Yu. A. Egorov, Scintillation Spectrometry of y Rays and Fast Neutrons [in Russian], Gosatomizdat, Moscow (1963). 547 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 3. D. I. Konstantinov et al., in: Dosimetry and Radiation Protection, Issue 6 [in Russian], Atomiz- dat, Moscow (1967), p. 121. 4. Yu. A. Sapozhnikov, V. A. Lopatin, and V. P. Ovcharenko, At. Energ. , 40, No. 3, 246 (1976). 5. H. Hurwicz, G. Reau, and M. Storm, in: Physics of Intermediate Reactors [Russian translation], Gos- atomizdat, Moscow (1961), p. 382. EXAMINATION OF IRRADIATED METAL DIBORIDES BY X-RAY DIFFRACTION Kh. i. Maile, I. A. Naskidashvili, UDC 154-162:539.16.04 and T. Sh. Berdzenishvili It has been shown [1-4] that metal diborides exposed to high thermal-neutron fluences (? 1020 neutrons/ cm2) undergo considerable changes, even extending to failure. We consider that these changes are due to the production of helium atoms, which escape from the matrix and accumulate in the intergranular pores. How- ever, the neutron fluence required to causefailure in metal diborides is reduced by up to a factor 100 if the material is irradiated at 15?K [5]. This result cannot be explained in terms of the above mechanism, because it is unlikely that the escape of helium from the matrix will be accelerated on reducing the temperature. For this reason we examined the changes in lattice parameters of titanium and zirconium diborides and the corresponding changes in unit-cell volume produced by low-temperature irradiation in a nuclear reactor. The specimens of ZrB2 and TiB2 were plates of size 10 x 15 x 1.5 mm, which were examined before and after irradiation by x-ray diffraction with a DRON-1 diffractometer at room temperature. Photographic powder patterns were recorded for the specimens; the diffraction lines were broad rings composed of indi- vidual spots. The distortion of the line shape caused by the large grain size was eliminated with the DRON-1 by oscillating the specimen in its own plane. The specimens were irradiated in low-temperature channels of the reactor at 110 and 300?K, where the temperatures did not fluctuate by more than ?5?K throughout the irradiation. Figures 1-3 and Table 1 give the results for the ZrB2 and TiB2 specimens, in which the changes in lat- tice parameters La/ain and 6.c/cin are given along with the changes in unit-cell volume ?V11. The reflec- tions from the irradiated specimens are displaced towards smaller angles (the more so the higher the fluence), which indicates an increase in the lattice parameters, which is usually caused by interstitial atoms or groups. As the lattice parameters were measured at room temperature (although the specimens were irradiated at 110?K), only the helium atoms will largely persist as free interstitial atoms out of all those produced by the irradiation (the helium is derived from the 10B). Therefore, the observed increase in the lattice parameters, particularly in the c parameter, must be due to predominant accumulation of interstitial helium atoms in the lattice. Table 1 shows that (Lic/c)/(Atz/a) 1 fpr ZrB2 on low-temperature irradiation, which apparently means that the lattice of ZrB2 retains more helium atoms than does TiB2. This is due on the one hand to the smaller size of the pores in TiB2 (be- cause the lattice parameters are smaller than those of ZrB2) and on the other to the stronger bonds between the atomic layers of metal and boron in TiB2 [1, 3, 6], and therefore the helium atoms are ejected from the TiB2 matrix more readily. If we assume that the change in lattice parameters is due in the main to intersti- tial helium, we have that the microcracks and failure are due to the internal stresses set up by these inter- stitial atoms, not to the marked increase in the helium pressure in the pores. If on the other hand the cause of the failure were such pressure rise, then reducing the radiation temperature, which greatly reduces the mobility of the helium, should mean that the failure would occur at higher neutron fluences. However, the failure in T1B2 in fact occurs at a much lower neutron fluence on reducing the irradiation temperature to 110?K [3-5]. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp,. 42-44, July, 1979. Original article sub- mitted December 28, 1977. 548 0038-531X /79/4701-0548S07.50 ?1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 TABLE 1 1110 20 15 10 Specimen Low-temperature irradiation Titr = "13?K T ? 3= 00?K ur radiation dose, neutrons/cm2 Aa % Ac % AV oz, An 04 Ac AV gin cin Vin "' . ain " % ein % viri ZrB2 54016 2.1016 1.1017 -- 0,08 0,19 0,04 0,10 0,42 0,04 0,26 0,80 0,01 0,04 0,21 0,01 0,06 0,35 0,03 0,14 0,77 TiB2 2.1016 1.1017 5-1017 0,04 0,10 0,46 0,01 0,08 0,25 0,09 0,28 1,17 -- 0,08 0,34 -- 0,06 0,22 -- 0,22 0,90 High-temperature irradiation (4] T 1.1T = 57 09X ZrB. TiB, 1070 1070 0,30 1,50 0,23 0,13 0,83 3,13 65 60 55 50 Zr 62 123 134 735 736 20- 153 154 155 2/9 Fig. 1 . Fig. 2 . Fig. 1. The (023) diffraction peaks of TiB2 specimens: I) not irradiated; II) exposed to a neutron flu- ence of 1.1017 neutrons/cm2 at 110?K; ILI) the same for 5.1017 neutrons/cm2. Fig. 2. The (123) diffraction peaks of ZrB2 specimens: I) not irradiated; II) exposed to a neutron fluence of 2.1016 neutrons/cm2 at 110?K; III) the same for 1.1017 neutrons/cm2. No matter what the irradiation temperature, the maximum increase in unit-cell volume for ZrB2 before the onset of failure is about 0.8%; we therefore conclude that there is a critical concentration of interstitial atoms in ZrB2 above which the expansive force becomes greater than the binding forces between the alternat- ing crystallographic basal planes. This leads to mechanical failure of the crystal. Prolonged irradiation results in reduction in the grain size of the crystal without change in the increment in cell volume, whose value remains around 0.8% for ZrB2. Figure 3 shows that the increase Ac/c produced by the radiation in ZrB2 is almost completely elimina- ted by annealing the specimen at 670?K, whereas Aa/a is then reduced by only 70%. This explains the differ- ences in the data on the lattice-parameter changes obtained on low-temperature and high-temperature forms of irradiation for ZrB2. At high temperatures (Tirr 600?K), the helium atoms escape into the intergranular pores, and only atoms bound to lattice distortions remain in the diboride lattice, and the concentration of these is much lower. Therefore, the diboride withstands a much higher neutron fluence at high irradiation temperatures because most of the helium remains in the lattice at low temperatures. When specimens irradiated at 15 or 120?K are heated to room temperature, there is fairly substantial annealing of the radiation-induced defects [5], and it is therefore obvious that the stages of isochronous an- nealing seen in the radiation-induced increase in the lattice parameters at 300-670?K (Fig. 3) cannot be due to annealing of single defects. These stages in the annealing may be due to the flow of various defect com- plexes to sinks (helium atoms plus vacancies, pairs formed by interstitial atoms with lithium, etc.), or else the breakup of these into isolated defects, which at these temperatures also migrate to sinks. 549 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Fig. 3. Isochronous-annealing curves for the radiation-induced increases in lattice parameters for zirconium di- boride: 0) Ac/Aco; *) 11a/ [Sao. Therefore, these results and the available evidence [2-5] indicate that the failure in metal diborides during reactor irradiation is due mainly to internal stresses in the matrix produced by interstitial helium atoms. Z. A. Titik assisted in the experiments, and we are also indebted to 0. I. Yurina for assistance with the calculations and to our colleagues on the nuclear reactor at the Institute of Physics, Academy of Sciences of the Georgian SSR, for general collaboration in performing the low-temperature irradiations. LITERATURE CITED 1. G. V. Samsonov, At. Energ. , 14, No. 6, 588 (1963). 2. V. V. Ogorodnikov et al., At. Energ., 23, No. 4, 341 (1967). 3. G. V. Samsonov et al. , At. Energ. , 24, No. 2, 191 (1968). 4. M. S. Kovalfchenko and V. V. Ogorodnikov, Fiz. Khim. Obrab. Mat., No. 4, 14 (1971). 5. L. S. Topchyan et al., At. Energ. , 42, No. 3, 226 (1977). 6. G. V. Samsonov, Dokl. Akad. Nauk SSSR, No. 83, 689 (1953). NEUTRON SPECTRA IN THE MeV RANGE IN FAST CRITICAL ASSEMBLIES V. M. Lityaev, V. A. Dulin, UDC 621.039.51 and Yu. A. Kazanskii Neutron spectra are extremely important reactor characteristics, because the quantitative aspect of any process in a reactor may be represented by averaging the neutron interaction cross sections over the neutron spectrum. A spectrum itself is dependent in a complicated fashion on the cross sections for inter- action of the neutrons with the materials in the reactor. Further, the theoretical spectrum is also dependent on the approximation used in the treatment. Therefore, neutron-spectrum measurements in reactors are of some interest. Measured and theoretical values provide refinement of the inelastic-scattering matrix for 238k and estimation of the error of the group approximation arising near fission thresholds and thresholds for (n, 2n) reactions. A scintillation spectrometer with y-ray discrimination by decay time in a stilbene crystal of diameter 7 mm and thickness 8 mm was used to measure the neutron spectra at the centers of three critical assemblies; this crystal was mounted in a Teflon jacket with a wall thickness of 2 mm. The working principle has been described previously [1]. The energy scale was calibrated from the upper limits of the Compton distributions given by y rays of known energy from 137Cs, 22Na 65Z n, -- RR Y sources and the 4.42 MeV y-ray line from a Po- a-Be source. The spectrometer was also calibrated with monoenergetic neutrons from a Van der Graaf ac- celerator. The reference neutron source was a miniature isotropic 252Cf source. The apparatus recoil-pro- ton spectra were converted to neutron energy spectra by differentiation [2] with respect to energy with a vari- able step (-1-E) (Fig. 1). A correction was made for the edge effect [3], whose values were 1 and 13.5%, re- spectively, at 0.8-1.4 and 6.5-10.5 MeV. In measurements on the 252Cf source, the temperature in the energy range 0.4-10 MeV was 1.41 ?0.03 MeV, which agrees with published values. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp.44-45, July, 1979. Original article submitted January 30, 1978. 550 0038-531X/79/4701-0550$07.50 1980 Plenum Declassified and Approved For Release 2013/02/15: CIA- Publishing Corporation RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 14 12 10 4 2 2,0 4 1,5? S -4 2 45 0 2 4 6 8 E, MeV ?,51.0 1,4 1,8 Fig. 1 Fig. 2 Fig. 1. Neutron spectra: 1) at the center of the BFS-35-1 assembly; 2) the same for the BFS-33 assembly; 3) for a 252Cf source. 2,2 E, MeV ? Fig. 2. Ratio K(E) of the measured spectra to a 1/E spectrum for the following assemblies: 1) BFS-30; 2) BFS-35-1. TABLE 1. Measured and Calculated Neutron Fluxes Assembly Energy range, MeVMeV g'exp TleX p. ',Pith with matrices given in [7] [8] BFS-30 10,5--6,5 0,01047 0,878 0,914 6,5-4,0 0,0636 0,887 0,886 4,0--2,5 0,1640 0,965 0,927 2,5--1,4 0,3510 1,050 1,044 0,459 1,4-0,8 0,4107 0,996 1,018 0,0317 BFS-33 10,5-6,5 0,0114 0,943 1,029 6,5-4,0 0,0792 1,092 1,115 4,0--2,5 0,1675 0,991 0,950 2,5-1,4 0,3208 0,968 0,957 0,461 1,4-0,8 0,4212 1,015 1,037 0,0291' BFS-35-1 10,5-6,5 0,01432 1,225 0,225 6,5--4,0 0,0755 1,282 1,083 4,0-2,5 0i1521 1,197 1,998 2,5--1,4 0,2820 1,161 1,046 0,457 1,4--0,8 0,4761 0,851 1,959 0,0274 1/E 2,5-1,4 0,467 neutron spectrum 1,4-0,8 0,0338 The main errors in measuring the neutron spectra' arise from errors in converting the pulse-height dis- tributions to energy spectra; if one assumes that the Terrell analytical representation applies for a fission- neutron spectrum of 252Cf, the likely error in determining the neutron flux at 10 MeV relative to 1 MeV is about 15%. The BFS-30 assembly has a composition close to that in the high-enrichment zone of a fast power re- actor with oxide fuel and sodium cooling, while the BFS-33 and -35-1 were constituted by media of uranium oxide and metallic uranium whose enrichment was such as to produce Keo 1 [4, 5]. The neutron fluxes were calculated by means of the M-26 program [6] with the BNAB-70 constants [7] (see Table 1). Table 1 also gives the ratios of the measured group neutron fluxes cpi to the theoretical ones for the various inelastic-scattering matrices for 238U [7, 8]. The differences between the group fluxes 551 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 calculated with the various a matrices increase with the ratio of 238U to 235U (this was 16.8 for the BFS- 35-1 assembly) and as the proportions of constructional and moderator materials decrease. The measured group fluxes agreed best with those calculated from the matrix of [8]. Figure 2 shows how the measured neutron spectra differ from a 1/E spectrum. Table 1 also gives the mean group fission cross sections for 2381J [9] as obtained by averaging for a 1/E spectrum and as derived from the measured spectra. The chan- ges in the mean fission cross section for 238U are, respectively, ?1.2%,-1.1%, and-2%fortheBFS-30,-33, and -35-1 when the measured neutron spectra are used instead of a 1/E spectrum in the averaging. The value of the theoretical neutron flux above 6 MeV is important in correct allowance for the (n,2n) reactions on 239PU (23Na, 238U); Table 1 shows that the calculations and measurements are in agreement in this regi013. LITERATURE CITED 1. F. Brooks, Nucl. Instrum. Meth., 4, 151 (1959). 2. C. Lanczos, Applied Analysis, Prentice-Hall (1956). 3. Fast-Neutron Physics [in Russian], Vol. 1, Gosatomizdat, Moscow (1963). 4. V. A. Dunn et al., At. Energ., 40, No. 5, 377 (1976). 5. E. N. Kuzin et al., FEI-698 Preprint, Obninsk (1976). 6. Sh. S. Nikolaishvili et al., in: Proceedings of the Trilateral Soviet?Belgian?Dutch Symposium on Fast- Neutron Physics [in Russian], Vol. 1, Izd. TsNHatominforma, Moscow (1970), p. 37. 7. L. P. Abagyan et al., Group Constants for Calculations on Nuclear Reactors [in Russian], Atomizdat, Moscow (1964). 8. A. S. Krivtsov and V. I. Popov, in: Neutron Physics [in Russian], Vol. 4, Izd. TsNHatominforma, Moscow (1977), p.113. 9. Y. Stehn et al., BNL-325, Supp. No. 2 (1965). EFFECTS OF VARIOUS FACTORS ON THE ABSORBED-DOSE DISTRIBUTION IN THIN LAYERS V. V. Krayushkin UDC 539.12.08 A specified distribution of absorbed radiation energy within the object must be provided in applied radiation-treatment systems, including industrial ones; we have examined the distribution of the absorbed dose D over the thickness of the material in relation to the angle of incidence of the electron beam, and also the effects of back-scattering metal plates on the distribution of D in thin layers (thickness less than the electron stopping length). The experiments were performed with electrostatic accelerators at energies of 0.3-1.0 MeV. A thin foil in the exit window resulted in a virtually monoenergetic electron beam. The dosimeters were cellulose triacetate (CTA) films of thicknesses 70 and 140 Am (p = 1.25 g/cm3), which simulated thin layers of the target material. The value of D was determined from the difference in the optical densities of the CTA films be- fore and after irradiation as measured with an SFD-2 spectrophotometer by a standard method [1] giving a coefficient of variation of ?8%. Stacks of CTA films were used to adjust the thickness. The distribution of D in a homogeneous material exposed to a beam incident at right angles containing electrons of energy 0.3-2.0 MeV can be put as D (x) r=(Dmax/2) [I +sin (0.2 ? 0x)], (1) where x is measured in the material in g/cm2, Dmax is the maximum value of D within the material, and is a parameter dependent on the electron energy [2]. Experiments with these CTA films were performed with the electrons incident at various angles a, which led to the empirical formula Da (x)=-- [(1 ? cos a)/41 Dmax (1+ sin [4.7 ? (0? ? 4.5) cos a]). (2) Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 46-47, July, 1979. Original article sub- mitted February 13, 1979. 552 0038-531X/79/4701-0552$ 07.50 0 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 44 1,0 48 -? 46 82 44 42 42 0,4 0,6 0,8 1,0 1,2 Thickness, mm 1,4 1,6 1,2 10 :74 48 gz.1 0,6 !?- C 44 0,2 44 co 1,2 1,6 2,0 2,4 Thickness, mm 28 Fig. 1 Fig. 2 Fig. 1. Distribution of the absorbed dose over the thickness of CTA films for angles of inci- dence of the electron beam of 0 (1), 20 (2), 40 (3), and 60? (4) (the points are from experiment). Fig. 2. Absorbed-dose distributions for specimens of thickness 0.84 (1), 1.68 (2), and 2.1 mm (3); (4) material irradiated without a substrate (semi-infinite geometry). 1,4 1,2 T; 40 48 42- 46 0 0,1 0,2 0,3 0,4 410 10 20 30 40 50 Thickness, mm Fig. 3 Fig. 4 Fig. 3. Reflected-dose factor in relation to atomic number of metal substrate at energies of 0.4 (1), 0.7 (2), and 1.0 MeV (3). Fig. 4. Absorbed-dose distribution in CTA films of thickness 0.42 mm exposed to 0.5 MeV electrons on substrates of: 1) lead; 2) nickel; 3) aluminum; 4)no substrate (semi-infinite ge- ometry); the points are from experiment and the lines are from theory. 'ref 44 3 60 70 80 Z 45 46 If the beam is incident normally, i. e., if cos a = 1, then (2) becomes (1). Figure 1 shows the distribution of D over the CTA films for various angles of incidence at 0.5 MeV; there is agreement to within ?7%. It is also of interest to examine the distribution of D in a layer of material irradiated on a metal substrate, since then there is back-scattering from the metal substrate if the thickness of the material is less than electron range, and therefore there is an increase in D near the surface of the substrate. The metals used in the experiments were aluminum, iron, nickel, copper, tin, brass, and lead. These were used as plates of thickness 1 mm (this thickness was greater than the electron range in the relevant ener- gy), and these were fitted with several CTA films assembled in stacks. Figure 2 shows the distribution of D in material on a tin substrate exposed to a 0.8-MeV beam. The value of D in the material increases the more substantially the less the thickness for a given electron energy. The distribution of D over the thickness on irradiation on a metal substrate can be put as the sum of two functions: D t(x)=-- r D (x) for x < 2a ?4,5/0; 1 D (x)? TfrefD (24 ?x) for x > 2a ?4,510, Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 (3) 553 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 where D(x) is the distribution of D when the material is irradiated without a substrate by a beam in normal incidence, as (1) shows, and nlref is the dose factor representing backscattering from metal substrate i, and a is the thickness of the irradiated material in g/cm2. The backscattering correction factors were determined by experiment with the beam incident normally on the target for various electron energies; D increased for CTA films on metal substrates of high atomic number (under otherwise equal conditions). Graphs were drawn up relating the backscattering factor to the atomic number for various electron energies (Fig. 3). The results for the effective reflection factor are in good agreement with the measurements of [3]. Figure 4 shows the distribution of D for material on substrates of various metals for an electron energy of 0.5 MeV; the following formula was devised to calculate D for various angles of incidence in the presence of backscattering substrates: Da (x) for x < 2a-4.5/0; Dat (x) = (x)? riref Da (2a ?x) for x> > 2a ?4.5/0. (4) The observed and calculated values agreed to within ?10%, which indicates that one is justified in using empirical formulas (2)-(4) to calculate the major parameters of radiation-treatment systems. LITERATURE CITED 1. A. K. Pikaev, Dosimetry in Radiation Chemistry [in Russian], Nauka, Moscow (1975). 2. V. V. Krayushkin and V. P. Suminova, in: Proceedings of the Second All-Union Conference on Indus- trial Uses of Charged-Particle Accelerators [in Russian], Vol. 1, Izd. NIgFA, Leningrad (1976), p. 347. 3. W. Bothe, Ann. Phys., 6, 44 (1949). A CALORIMETER FOR MEASURING LOCAL ELECTRON-BEAM ABSORBED DOSES V. A. Berlyand, V. V. Gen eralova, UDC 539.12.08 and M. N. Gurskii Electron beams of energy between 0.2 and 10 MeV are widely used in radiobiology, industrial applica- tions, and research in many areas; exact measurements on absorbed dose are performed by means of point dosemeters or calorimeters. Many such calorimeters have been described [1] for electrons of energy over 1-2 MeV. The instrument of [2] allows measurements to be made at electron energies above 150 keV; a single component acts as absorber, temperature transducer, and heater, namely a conducting polyamide film [3], which is made from polyamide lacquer with the addition of carbon black. These films are of high thermal stability and can work at temperatures of 350-400?C for several months or briefly (a few hours) at 450-500?C; the radiation resistance of such a film is also higher by several orders of magnitude than that of the most radiation-resistant polymer, polystyrene. The thickness of the film can be varied over the range 1.5-6 mg/ cm2. The carbon content is 20-40 mass%. Measurements show that the thermal defect is not more than 0.3%. The temperature coefficient of resistance of the material is negative, # = ?0.0004, and this is less by about an order of magnitude than the values for copper and platinum, but the value is still quite sufficient for the measurement of dose rates above 103 rad/sec. The calorimeter proper is a strip of this film 10 x 20 mm; the inherent resistance is ?200-300 SZ, and this is inserted in one arm of a de bridge. The bridge is balanced by adjusting the input current at some tem- perature Tb, which is above the environmental temperature. The absorbed dose rate.P is defined by p (I? ? 11) R Tb (1) Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 47-48, July, 1979. Original article submitted March 23, 1976; revision submitted February 6, 1979. 554 0038-531X/79/4701-0554807.50 01980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 1 2 3' 4 5 1/ \ r-c \ A Fig. 1. The dose-rate meter: 1) calori- meter; 2) screen of diameter 40 mm; 3) nylon filaments; 4) radiator; 5) hole of diameter 35 mm; 6) mounting ring; 7) screening body of 60-mm diameter. where I and 12 are the currents in the device for which the bridge is balanced before and during the irradiation respectively, while R(Tb) is the resistance of the device at temperature Tb and M is the mass of the device. Instruments have been devised in uhf engineering [4] for keeping such bridges constantly in balance automati- cally; these can be used in conjunction with this ealorimeter in ionizing-radiation dosimetry. In our dosemeter (Fig. 1), the calorimeter is surrounded by screens also made of the same material in order to minimize effects from' environmental-temperature fluctuations and convection. The distance between the calorimeter and the screen is 1 mm. .The design of the mounting ring allows radiators of various materials to be mounted on both sides, and it is therefore possible to make measurements in any material at any depth. The screens and the calorimeter are made of the same material, so the radiation itself sets up quasiadiabatic conditions. If the measurement time is much less than the time constant of the calorimeter, which is about 30 sec, one can assume that P = k (dR I dt), (2) where dR/dt is the rate of change of the resistance and k is a coefficient of proportionality. This means that measurements can be made in dynamic mode, which is often preferable, because the electron-beam intensities are high and the time stability is poor. This instrument in principle provides a means of precision dose-rate measurement; the calorimeter employing this material contains no foreign materials and therefore there are no errors due to energy deposi- tion in foreign inclusions. The material combines the functions of absorber, heater, and transducer, and therefore there is virtually complete identity in the substitution of electrical heating for radiation heating. The systematic error in dose-rate measurement is 0.7% at the 0.95 confidence level, while the random error, expressed as the coefficient of variation, is not more than 2%. The calorimeter provides for dose-rate mea- surement on electron beams between 103 and 2.107 rad/sec for electron energies from 0.15 to 10 MeV or more, while it substantially simplifies the methods used in calibrating film chemical dosimeters in which a total-ab- sorption calorimeter is required [5]. Also, the film calorimeter can be used in the dosimetry of photon radia- tion, including low-energy x rays, as well as the p radiation from large radiation sources. , LITERATURE CITED 1. S. Gunn, Nucl. Instrum. Meth., 85, No. 2, 285 (1970). . 2. V. A. Berlyand, V. V. Generalova, and M. N. Gurskii, Inventor's Certificate No. 593554, Byull. Izo- bret. , No. 39, 212 (1978). 3. V. E. Gul', V. F. Blinov, and M. G. Golubeva, Plastmassy, No. 9, 45 (1976). 4. M. I. Bil'ko et al., UHF Power Measurement [in Russian], Soy. Radio, Moscow (1976). 5. V. A. Berlyand et al., At. Energ. , 42, No. 3, 199 (1977). 555 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 DETERMINATION OF NUCLEAR CONSTANTS AS AN INVERSE PROBLEM IN RADIATION TRANSPORT V. N. Dushin UDC 539.125.52 The values of nuclear constants obtained by measurement are distorted by various effects arising from the finite dimensions of the systems, including attenuation of radiation fluxes, multiple scattering, etc. The requirements of reactor engineering impose closer tolerances on the determination of constants, and these can no longer be met by correcting for such effects via average factors or terms. Therefore, one has to con- sider the extraction of nuclear constants from the data of neutron experiments as an inverse problem in the theory of radiation transport [1], for which we give a method applicable to the real geometry, and for which we demonstrate the good performance in recovery of an inelastic-scattering cross section. We write the transport equation for the system as (x)--- K (x' x)(1)(x')dx' S (x), (1) where 4,(x) is the particle-collision density, x= (r, S2, E), S (x) is the collision density for the first collision, and K (x' ?x) is the kernel of the transport equation. The unknown parameters (cross section, scattering indicatrix) appear in K(x' ?x). The collision density 4,(x) is measured or is calculated from measurements for various values of x and is therefore known approximately. This 4,(x) may not correspond to any physical kernel K(x, ?x), and therefore one has to avoid solving the inverse problem in the ordinary sense of the word and instead consider the definition of some general solution. Following [2], we take the functions a (x) as the solution (o- (x) are the desired nuclear constants), which are such as to provide IP 0= if (a), o(x)EC where V (a) (x)-4)2 (x)j2 dx. Here 4.e(x) is the experimental collision density, while 4) (x) is the collision density calculated by means of o-(x),andD is the region of definition (measurement) of 4)e (x), 4, (x)? L2; the condition for physical reality of the target parameters requires that (2) (3) (4) Therefore, the inverse problem in radiation transport amounts to defining the turning point in the function of (3) subject to conditions (4) and (1). The Monte Carlo method is used to solve (1) on account of the complexity of the geometrical conditions in real experiments; this makes the problems stochastic. Stochastic quasigra- dients [3] are used in solving stochastic turning-point problems, where this gradient is a random quantity whose mathematical expectation is similar to a gradient or generalized gradient in a certain sense. The turn- ing point is defined by a sequence of random vectors as, s= 0, 1, 2, ...; as+i = nx (as? psvs); s= 0, 1, 2, ..., (5) where Irx is the operator for projection of the acceptable values of the parameters a on the region; uo is an arbitrary initial point, as is the step size, and vs is the stochastic quasigradient vector, whose mathematical expectation is M (v'/a?, GI, GS) - slir (as)?b'. (6) Here as is a nonnegative random quantity, bs is a random vector, and ira(crs) is the vector for the generalized gradient, i.e., a vector that for any z satisfies Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 48-50, July, 1979. Original article submitted May 22, 1978. 556 0038-531X/79/4701-0556807.50 0 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 4 ? A A A ? A A A A A A I 2 4 6 6 10 Iterations 12 /4 402- 0 0,913- b 0,015 4?1 4005 0 1 2 3 4 E, MeV Fig. 1 Fig. 2 Fig. 1. Convergence of the minimization in a model experiment; specimen size about 0.5 mean free path. Fig. 2. Results from processing inelastic-scattering spectra for neutrons in lead; a) recovered cross section; b) solid line ? observed spectrum, broken line ? spectrum calculated from recovered cross section. ,11 (z)?T (as) Oa (a.), z ? a.). (7) The process of (5) may not give a monotonic reduction in the target function 4,(o-) at each step, and this is a qualitative difference from the usual gradient method. Some theorems [3, 4] ensure that the process of (5) converges in an infinite number of steps. Only a restricted number of tests can be performed in a practi- cal case, which is equivalent to restricting the processing time, and this requires the introduction of some statistical criterion that will provide some given error level in the functional, Such a criterion can be used with known values for the variances of 4) (x) and ,I)e (x) to estimate whether a statistically significant deviation of 4, (a) from zero occurs, and therefore to determine the points at which the search is stopped. If the target function does not decrease during the minimization and also remains statistically significant, this means either that the gradient describing the radiation transport is inadequate to describe the experimental conditions or that there are systematic errors in the experimental data. As an example, we give results on the inelastic-scattering cross section for neutrons of energy 4.7 MeV [5]. The experiments were performed at the Khlopin Radium Institute with cylindrical geometry by the time- of-flight method. A program was written for the BESM-6, which used a subroutine for solving the transport equation by Monte Carlo methods. Local estimation of the neutron flux is employed [6] together with statisti- cal weights that incorporate the loss of neutrons from the specimen and the absorption. Random termination of the paths was also incorporated. The partial derivatives of the flux required to calculate the stochastic quasigradient were estimated at the same time as the neutron flux itself [7]. The workability of the algorithm was checked out on a model experiment. The spectrum of inelastically scattered neutrons calculated in this way was used to recover the initial model cross section. Figure 1 illustrates the convergence of the minimi- zation, where 6 is defined as 6= {s (Fexp(E)?F (E)121F (E) "2. (8) Here Fexp (E) and F (E) are the measured and calculated neutron fluxes; as Fexp (E) and F (E) are calculated with an error of about 1.6%, we can say that the minimization converges in 5-7 iterations. 557 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 This method was used to recover inelastic-scattering cross sections from experiments with specimens of size up to two mean free paths. Figure 2 shows a typical example. This method can also be used to optimize the shape and size of the specimen, as well as the parameters of the time-of-flight spectrometer. LITERATURE CITED 1. A. V. Vantkpv, in: Nuclear Science and Technology, Nuclear Constants Series [in Russian], No. 16, Atomizdat, Moscow (1974), p. 11. 2. A. N. Tikhonov and V. Ya. Arsenin, Methods of Solving Incorrectly Formulated Problems [in Russian], Nauka, Moscow (1974)? 3. Yu. M. Ermol'ev, Stochastic Programming Methods [in Russian], Nauka, Moscow (1967). 4. Yu. M. Ermol'ev and Z. V. Nekrylova, Kibernetika, 6, 4 (1966). 5. V. N. Dushin et al. , [1], No. 24 (1977), p. 27. 6. V. G. Zolotuldiin and S. M. Ermakov, in:-Physics of Reactor Shielding [in Russian], Gosatomizdat, Moscow (1963), p. 171. 7. E. V. Pletnikov and G. Ya. Trukhanov, [1] (1974), p. 106. EFFECTS OF BOMBARDMENT BY He, Nit, AND Cr+ ON MICROHARDNESS AND CORROSION CRACKING OF STAINLESS STEELS B. G. Vladimirov, V. M. Gusev, UDC 620.197 and V. S. Tsyplenkov One reason for the failure of components made of stainless steels and alloys working at elevated tem- peratures in water or water?steam mixtures is intercrystallite corrosion followed by cracking under stress [1]. The cracks arise under such conditions at the solid?liquid (or solid?gas) interface, where the state of the metal surface largely determines the rate and type of corrosion failure, particularly in the initial stages. Improved resistance to corrosion cracking is provided by mechanical treatment that produces compressive stresses in the surface layer [2-4]. Also, bombardment with various ions alters the mechanical and physicochemical parameters of the sur- face layers because the implanted ions produce chemical effects and various defects. In particular, the im- plantation of He+, Ni+, and Cr+ has been used to improve the corrosion resistance in metals [5, 6]. It is therefore of interest to examine the scope for improving the corrosion resistance of stainless steel by surface treatment with He+, Ni+, and Cr+ ions at energies of rather more than 10 keV. Methods Rectangular plates (size 80 x 5 x 0.6 mm) of stainless steels type OKh16N15M3B of the austenite class (after heating to 1050?C) and type 1Kh13S2M2 of the ferrite ?martensite class (after annealing at 850?C) were used with grain sizes of 20-30 tim. The steels were bombarded with He+, Ni+, and Cr+ ions at 40 keV in an ILU-3 accelerator [7] at a cur- rent density of 15-20 ?A/cm2 to a total dose of 1018 ions/cm2. The specimens were set up in two different de- vices. One of these provided for maintenance of a set temperature during irradiation (e.g., 500?C on treat- ment with Cr+ ions). In the other, the specimens were mounted on a water-cooled table. However, the poor thermal contact meant that the temperature indicated by a Chromel?Alumel thermocouple rose to about 100?C during the bombardment. The corrosion tests on the original and irradiated specimens were performed in an autoclave made of OKh18N1OT steel of volume 0.35 liter with an aqueous solution of FeC13 having a chloride concentration of 100 Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 50-51, July, 1979. Original article submitted June 26, 1978. 558 0038-531X/79/4701-0558807.50 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 TABLE 1. Results of Tests on Corrosion Cracking of Steels in FeC13 at 360?C and a Pressure of 190 mm Hg (chloride concentration 100 mg/liter) DoOingele- ment (ion) Irradiation temperature ?C Time to failure, h OKh16N15M13B 1Kh13622v12 He Ni + Cr + Cr + Original specimen ?100 ?100 ?100 ?500 350 350 230 30 130 90 30 60 70 40 210 190 170 150 . 130 ...vaa 210 2 no 170 150 130 110 0 20 40 60 80 0 20 40 60 80 Distance from surface, um Fig. 1. Change in the microhardness of steels type OKh16N15M3B (open circles) and 110113S2N2 (filled circles) over the cross section after surface implantation at 100?C of helium (a), nickel (b), and chromium ions (c), and also chromium at about 500?C (d). mg/liter at 360?C and 190 mm Hg. The stresses in the specimens were produced by bending in a circular mount [1]. The strain in the stretched outer surface layer after bending was 5%. Constant strain during the test was ensured by contact welding of the ends of the specimen. The onset of failure (occurrence of crack- ing) was observed by examination with an MBS-2 microscope every 10 h in tests lasting up to 100 h, 20 h for tests lasting up to 200 h, and 90 h for tests lasting up to 500 h. The FeCl3 solution was replaced after each cycle; the tests were continued until the first visible crack appeared. Also, a PMT-3 instrument was used with a load of 100 g to measure the microhardness at various depths by oblique-section methods. Experiment Results The measurements showed that irradiation of Olch16N15M3B steel with nickel, helium, or chromium ions at temperatures up to 100?C increased the microhardness down to depths of 40-60 pm; the ranges of He+, Cr, and Ni + ions of energy 40 keV in steel are [8] substantially less than 1 pm, and the change in microhardness to much greater depths may be due to radiation-stimulated diffusion of point defects and the formation of dis- location loops, which distort the lattice and harden the material [9]. Figure la-c shows that the implantation of the metal ions (nickel and chromium) produces a greater in- crease in the microhardness at the surface than does implantation of helium; however, helium produces a layer of constant hardness (1-42kgf/mm2) throughout a thickness of about 30 pm, whereas the metals produced a rapidly decreasing microhardness. A similar layer of thickness about 20 pm of constant but elevated micro- hardness (about 210 kgf/mm2) was produced by bombarding 1Kh13S2M2 ferrite-martensite steel with helium (Fig. la). 559 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Figure id shows that there is a complicated change in the microhardness for OKh16N15M3B steel ex- posed to chromium ions at 500?C; this is clearly the joint effect of several processes, some of which produce hardening and others softening. In particular, lattice distortion due to radiation defects and the formation of finely divided phases tends to harden the implantation layer. However, the radiation may also accelerate the stress relaxation. The peak (Fig. 1d) may reflect the joint effects of these various processes. Type 1Kh13S2M2 steel has a bcc lattice (Fig. lb-d), and stress relaxation appears to be the dominant effect on bombardment with metal ions. The corrosion results (Table 1) show that surface treatment with helium, nickel, and chromium ions at about 100?C substantially increases the time to failure for OKh16N15M3B steel; by a factor 2.7 for nickel and helium ions or by 1.7 for chromium. Table 1 shows that helium ions (and to a smaller extent chromium ions) also increase the time to failure for ferrite- martensite steel. Figure 1 and Table 1 show that there is a correlation between the change in microhardness and the cor- rosion resistance in the implantation layer, apart from the case of 1Kh13S2M2 steel exposed to Cr + ions. The improved corrosion resistance in the implantation layer may be due to a surface barrier of doping atoms, which prevents the chloride ions from diffusing into the metal and also may prevent the diffusion of oxygen and other corrosion stimulators. There was a certain increase in the corrosion resistance of 1Kh13S2M2 steel after bombardment with Cr+ undoubtedly on account of the surface-barrier effect. We are indebted to V. P. Voeikov for considerable assistance in performing the corrosion tests. LITERATURE CITED 1. V. P. Pogodin, V. L. Bogoyavlenskii, and V. P. Sentyurev, Intercrystallite Corrosion and Corrosion Cracking in Steels in Aqueous Solutions [in Russian], Atomizdat, Moscow (1970). 2. H. Suss, Corrosion, 18, No. 1, 17 (1962); 17, No. 2, 63 (1961). 3. X. Tozano, J. Jpn. Inst. Met., 24, No. 12, 786 (1960). 4. W. Ruttmann and T. Gunther, Werkst. Korros. , No. 2, 104 (1965). 5. Yu. M. Khirnyi and A. P. Solodovnikov, Dokl. Akad. Nauk SSSR, 214, No. 1, 82 (1974). 6. A. Autill et al., Corr. Sci., 16, No. 10, 729 (1976). 7. N. P. Busharov et al., Prib. Tekh. Eksp., 4, 19 (1967). 8. J. Lindhard, M. Scharff, and H. Schiott, Kgl. Danske Vid. Selskab, Mat.-Fys. Medd., 33, No. 14 (1963). 9. V. N. Bykov and V. A. Troyan, Phys. Status Solidi, 32, 53 (1975). NONSTATIONARY PROMPT-NEUTRON DIFFUSION IN A FAST ASSEMBLY V. E. Kolesov, 0. I. Makarov, UDC 621.039.514.4 and I. P. Matveenko The characteristic time dependence ipa (i-, V) exp (-a0t) occurs in experiments with pulsed prompt-neu- tron sources after the transient period, where a0 describes the asymptotic decay of the neutron pulse and is the same no matter what detector is used at any point in the system. If a0 is only slightly dependent on Fand V/ (which is typical of fast reactors), one says that there is a quasiasymptotic neutron-flux distribution. One can estimate the limits of an asymptotic or quasiasymptotic distribution by numerical calculation on non stationary processes; we restrict consideration to the multigroup one-dimensional nonstationary diffu- sion equation. The numerical method of solving this equation with two or three groups has been described [1]. Here we consider a multigroup treatment with over 20 groups. Consider the equation I ? div grad .7+ 27p :?Tp a n (1) Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 51-52, July, 1979. Original article submitted July 17, 1978. 560 0038-531X/79/4701-0560$07.50 0 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Alc 30 20 10 10 8 7 0 0 10 20 0,6 47 0,13 4g R/Rcr Time, 10-6 sec Fig. 1 Fig. 2 Fig. 1. Dependence of a/a er on radius for the BFS-32 assembly: solidline - fromtheory, points - from experiment. Fig. 2. Relative derivative of the count rate as a function of time for an assembly containing natural uranium dioxide (symbols as in Fig. 1). 30 subject to boundary and initial conditions of the form =?2: -P = --/q7; (r, It=o= (1)0 (r), an y where G is the number of energy groups, q (r, t) {(p (1) (r, t), (p(2) (r, t), , (pG (r, t)}; S is a lower trian- gular matrix of order G with nonnegative coefficients, T is the complete matrix of that type, and v-1, n, and 1 are diagonal matrices. There is always an asymptotic solution to (1), but the asymptotic distribution may occur after excessive time following the pulse, whereas we are interested in time intervals such that the neutron flux is still above the limit of detection of the instrument or above the background. We solve (1) by a difference method. The stationary-state approximation has been examined in some detail [2], so we pass at once to the differential-difference equation (2) ao7Pth -AniDh+ th(p-h, where Ah, vh, Th are difference approximations for the operators div 15 grad- E + S, v-?, T; then -(Ph (r, (pha (r) exp (-aot) for large times. It is necessary to follow the behavior of the flux from the start of the pulse to the steady-state value, so the difference scheme must be asymptotically stable [2]. Only a purely inexplicit scheme is unconditionally asymptotically stable amongst the various two-layer schemes for a parabolic equa- tion, so we apply the operator Ah to the upper t layer. The T matrix is complete, and this is more convenient to apply to the lower layer. The error in the asymptotic or quasiasymptotic state is reduced by introducing corrections in terms of solutions exponential in t. As a result 1x Rh (r, --ihs (r, t ?T)JPE= AnTlyr (r, l'hiCPht (r, t?r.), (3) where T is the time step and x = ?ch/Il ? exp (ccr)]; _ ( II (Thc (r, t ? 2T) cz??(Pits (r, t ? T) (4) The solution to (3) is found for each value of t by one-dimensional fitting for each group in sequence beginning with the first. The scheme of (3) has unconditional asymptotic stability and convergence, and calculations show that the corrections of (4) greatly improve the accuracy. It has been shown [3] for some simple cases (e.g., for Th = 0) that a ?aa, (ph, exp (at) ? (pha const for t Q0 for any r. In practice these conditions are met for any Th even in the more general case where the corrections of (4) are introduced separately for each group. 561 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 The scheme of (3) was implemented as the NESTOR program (nonstationary one-dimensional calcula- tion) in Algol for the M-220; the experimental results were made comparable with the calculations by the use of data for assemblies of two types. The first type was composed of a series of single-zone multiplication systems whose composition was close to the core composition used in fast power reactors (the BFS-32 assem- bly [4]). A characteristic of such a system is the presence of a quasiasymptotic neutron-flux distribution. Assemblies of the second type corresponded to continuous variation of the neutron spectrum in time. We used an assembly containing natural uranium oxide, which is the blanket material used in fast reactors. The methods of measurement anti the parameters of the apparatus corresponded with those of RI (Figs. 1 and 2). In the first case, a was calculated for detectors differing in spectral sensitivity e (E); the decrement a remained virtually constant after a transient period of about 1.5 ?sec for assemblies of radius from Rer down to 0.7 Rel.. Smaller assemblies gave a that varied appreciably with time and depended on the type of detector. Figure 1 shows data for a detector having e (E) = Z15(E), and in that case the relation a (t) =RAE, (P)] TP)/at after the transient period showed a part with very little slope (plateau). The maximum and minimum values of a given in Fig. 1 correspond to the initial and final instants as taken symmetrically about the middle of the plateau for falls in neutron flux by a factor 102. In the second case, the calculations and experiments were per- formed for a detector having e(E) = Ef8(E) and placed at the center of the assembly. A 26-group system of BNAB constants was used. The experiments and calculations confirmed that these approximations are applicable on calculations on the prompt-neutron kinetics in assemblies (down to Kef =0.7 or less). LITERATURE CITED 1. B. I. Kolosov, FEI-275 preprint, Obninsk (1971)? 2. A. A. Sarnarskii and A. V. Gulin, Stability in Different Schemes [in Russian], Nauka, Moscow (1973). 3. V. E. Kolesov and 0. I. Makarov, FEI-822 preprint, Obninsk (1978). 4. I. P. Matveenko et al., At. Energ. , 44, No. 3, 262 (1978). EFFECTS OF ION-BOMBARDMENT DOSE AND PREVIOUS SURFACE TREATMENT ON THE EROSION OF MOLYBDENUM B. A. Kahn, D. M. Skorov, UDC 539.12.04:621.039.616 and V. L. Yakushin Blistering under ion bombardment for some considerable time was considered [1-2] as the most impor- tant form of erosion of the first wall in a thermonuclear reactor [3, 4]. However, subsequent study showed that blistering in fact falls at high radiation doses [5, 6]. When neobium was bombarded by helium ions of energy 15 keV at 2 mA/cm2, the blistering vanished at doses of (6.25-18.75)?1018 ions/cm2 [5]. It was suggested that this was due to alteration in the distribution of the implanted gas when the tops of the blisters lift and that there is also an effect from cathode sputtering of the surface layer [5, 6]. The final topography is very much dependent on the irradiation conditions, in- cluding target temperature. It is therefore of interest to examine the effects of dose and previous treatment on the irradiation erosion of molybdenum, which is one of the promising materials for these discharge cham- bers. Vacuum-melted molybdenum of MChVP grade and TsM10VD alloy were polished mechanically before irradiation, with final finishing with diamond paste type ASM 1/0. Some specimens of the T5M10VD alloy were additionally polished electrolytically. The state of the treated surface was monitored with a 201 PS profilograph. The specimens were bombarded with helium ions of energy 20 keV at a beam cukrent density of 660 ?A/ cm2; the MChVB molybdenum was irradiated at 650?C to doses of (5-500)?1017 ions/cm2, while the T5M10VD Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 53-54, July, 1979. Original article submitted December 28, 1978. 562 0038-531X/79/4701-0562S07.50 @1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 41g g 417 g 0,15 415 409 4 8 12 16 20 B?10-7 ions/cm' 24 Fig. 1. Erosion coefficient of TsM10VD alloy in relation to dose. Fig. 2. Surfaces of specimens of TsM10VD alloy after dose of 1 -1018 ions/cm2 (a) and of vacuum melted MChVP molybdenum after a dose of 5-1018 ions/cm2 (b). was irradiated at 700?C with doses of (4.8-20)?1017 ions/cm2. See [71 for more details of the bombardment conditions. The surface topography was examined with an EMV-100L electron microscope by means of car- bon replicas shadowed with chromium and also with a Kwikscan-50 scanning microscope. The erosion coeffi- cient was deduced from the electron micrographs via the geometrical dimensions of the tops of the blisters, for which the numbers of atoms were calculated. Figure 1 shows the observed dependence of the erosion coefficient for TsM10VD in relation to dose; at first, the coefficient increases, but there is a peak in the range 1.4-1018 to 2-1018 ions/cm2. Figure 2a shows a typical electron micrograph of TsM10VD after a dose of 1-1018 ions/cm2. The surface has been substantially eroded, and most of the blisters have burst, with many of the tops leaving the surface of the material. It was found that mechanical polishing greatly reduced the tendency of the material to produce blisters that fail, especially by comparison with the eldctropolished material, at all doses in the range from 5-1017 to 5.1019 ions/cm2. For example, a mechanically polished surface showed no broken blisters, whereas electro- polished specimens under analogous bombardment conditions showed considerable erosion arising from bro- ken blisters (Fig. 2a). The suppression of blistering appears to be related to microscopic roughness of height 0.04-0.18 pm produced by mechanical polishing. This roughness prevents the gas from forming coplanar layers and thus hinders the union of helium bubbles into gas cavities, which represent the first stage of blis- tering. Electropolishing also hydrogenates and embrittles the surface layers of molybdenum, and this appears to favor erosion under irradiation. Doses between 5-1017 and 2?1018 ions/cm2 to MChVP molybdenum produced blisters; the blisters vanished on raising the dose to 5-1018 ions/cm2, but the surface of the material was etched, and cones of height about 0.7 pm were produced on further increase in the dose (Fig. 2b). Blistering is therefore a transient effect. LITERATURE CITED 1. W. Primak, Y. Dayal, and E. Edwards, J. Appl. Phys., 34, No. 4, 827 (1963). 2. W. Primak and J. Luthraf, Ibid., 37, No. 6, 2287 (1966). 3. R. Behrisch,Nucl. Fusion, 12, No. 2, 695 (1972). 4. E. Kemp, ibid., 14, No. 2, 277 (1974). 5. J. Martel and S. Jacques, in: Proceedings of the Conference on Surface Effects in Controlled Thermo- nuclear Fusion Devices and Reactors, Argonne, Jan. 10-15, 1974. 563 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 6. J. Roth and R. Behrisch, J. Nucl. Mater., 57, No. 3, 365 (1975). 7. D. M. Skorov et al., in: Proceedings of the All-Union Conference on Engineering Problems of Thermo- nuclear Reactors [in Russian], Vol. 3, NIAFA, Leningrad (1977), P. 226. A CADMIUM-SULFIDE y-RAY DOSIMETER WITH ELEVATED STABILITY UNDER IRRADIATION V. K. Dubovoi UDC 53.07/08+53.001.89 A major disadvantage of semiconductor y-ray dosimeters is that the irradiation resistance is poor, which hinders their use in high-power irradiation systems, where the exposure dose may be many kR/sec. In the present dosimeter, high radiation resistance is provided by the use of CdS crystals exposed to fast reactor neutrons. The radiation defects make these crystals homogeneous in bulk properties, while they have good sensitivity to y radiation and a specific resistance of 106-107 ohm ? cm, and the voltage-current response is linear up to fields of 300 V/cm. Ohmic contacts were formed with indium. The dimensions of the detectors were 0.5 x 0.1 x 1 cm, so they-ray distribution at the point of measurement is altered only slight- ly. The current Ly is measured with a constant voltage applied to the detector. Shunting by the ionized air is eliminated by sealing the transducer and fitting special microconnectors that eliminate current liakage. Fig- ure 1 shows the dosimeter characteristic, where ly is proportional to the square root of the exposure dose. There is an increase in Ly with temperature, and therefore in the sensitivity of the y-ray detector. Measure- ments were made of the current at a fixed exposure-dose rate of 50 R/sec for various photon energies Ev; it was found that the CdS dosimeters had only a slight hardness trend for y radiation. We used 60Co (Ey =1.17 and 1.33 MeV) and 137Cs (0.66 MeV) sources together with the y rays from a reactor, which are strongest at Ey = 0.3 MeV [1]. The radiation resistance in a y-ray field was determined from the Ly curves in relation to "Co y-ray dose at a dose rate of 6000 R/sec, the result being the value of -109 ,(Fig. 2). 3 2_,/ I 10 20 30 40 50 60 70 VP, sec /0 7 10 ' 8 10 9 DA R Fig. 1 Fig. 2 Fig. 1. Relation of ly to exposure dose for 60Co y rays at U = 5 V and T = 30?C. Fig. 2. Dependence of 17 on "Co exposure dose at U = 5 V, T = 30?C, and Py =6000 R/sec. LITERATURE CITED 1. V. M. Kolyada and V. S. Karasev, At. Energ. , 19, No. 6, 532 (1965). Translated from Atomnaya Energiya, Vol. 47, No. 1, p. 54, July, 1979. Original article submitted August 30, 1978. 564 0038-531X/79/4701-0564$07.50 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 THE THERMAL-NEUTRON FISSION CROSS SECTION AND THE FISSION-RESONANCE INTEGRAL FOR 2 4 3 CM K. D. Zhuravlev and N. I. Kroshkin UDC 539.172.4 Thermal-neutron fission cross sections of and the resonant-fission integral If for 243Cm have been mea- sured in determining nuclear constants for the actinides by the cadmium difference method; the standard was a 235U target, for which the thermal-neutron fission cross section was taken as 582.2 ?1.3 barn, while the resonant-fission integral was taken as 275 ?5 barn [1]. Measurements were made in a horizontal channel in the SM-2 high-flux reactor. The cadmium ratio for 235U was 40 when the neutron beam was filtered with lmm of cadmium. The uranium and curium targets were deposited on aluminum substrates of thickness 0.1 mm. The amount of substance in the target was about 1 ptg in each case, while the diameter of the target spot was about 4m 10 mm. The curium target had the following percent isotope composition; 242cm 0.la ? 0.07, 243cm 37.29 ? 1.34, 244Cm 61.61 ?1.34, 245Cm 0.94 ?0.10. The number of nuclei in the curium target was determined from the spontaneous fission rates of 244Cm and 242CM. The spontaneous-fission half-life of 244CM was taken as (1.270 ?0.007)407 yr, andthat for 242Cm was taken as (6.09 ?0.18)? 106 yr[2]. The number of nuclei in the uranium target was determined by a counting in 2n geometry. The isotope composition of the uranium target and the method of use have been described in detail [3, 41. The measurements led to correction of of and If for 243Cm (K2014 = 0.998, K244 = 0.987 and K2,745 = 0.937, K245 = 0.987), on account of the contents of 244Cm and 245CM, which relate respecTlively to the thermal-neutron fission cross section and the resonant-fission integral. The temperature of the neutrons at the reactor exit having a Maxwellian spectrum was 353?K [4], and the g(T) correction incorporated the fact that the fission cross section of uranium does not follow VIM so the value was 0.965 [5]. It was assumed for curium that the fission cross section follows 1/1/T and g(T) =1. Table 1 gives the fission cross section and resonance integral, which are in agreement within the error of measurement. The spread in the values is probably due to the lack of data on the behavior of the fission cross section of 243Cm in the thermal range. TABLE 1. Thermal-Neutron Fission Cross Section and Resonant Fission Integral for 243Cm in barn Parameter Our results Data of [1] Data of [6] cri 672+60 600+50 609,6?25,9 if 1480+150 1860+400 1575+136 LITERATURE CITED 1. Neutron Cross Sections, BNL-325, Third Edition, Vol. 1 (1973). 2. Yu. S. Zamyatnin, in; Nuclear Constants [in Russian], No. 14, Atomizdat, Moscow (1974), p. 22. 3. K. D. Zhuravlev, N. I. Kroshkin, and A. P. Chetverikov, At. Energ., 39, No. 4, 285 (1975). 4. K. D. Zhuravlev and N. I. Kroshkin, in: Atomic Science and Engineering, Nuclear Constants Series [in Russian], No. 19, Atomizdat, Moscow (1975), p. 3. 5. P. E. igeltstaff, in: Handbook on Nuclear Physics [in Russian], Fizmatgiz, Moscow (1963), p. 268. 6. C. Bemis et al., Sci. Eng., 63, 413 (1977). Translated from Atomnaya Energiya, Vol. 47, No. 1, p. 55, July, 1979. Original article submitted August 7, 1978. 0038-531X/79/4701-0565$07.50 ?1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 565 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 ABSOLUTE MEASUREMENT OF THE BRANCHING RATIO FOR THE 277.6-keV LINE OF 2 3 9Np V. K. Mpzhaev, V. A. Dulin, UDC 661.039.51 and Yu. A. Kazanskii It is common to measure the intensity of the 239Np y rays in order to determine the accumulation of 239Pu in breeder reactors; in some cases it is necessary to know the branching ratio of the 277.6-keV y-ray line in the decay of 239Np. Also, it has been suggested that the set of standard calibrated radioactive prepa- rations (from the IAEA) should contain 243AM instead of 293Hg. In that case it is also necessary to know the absolute yield of the y line of 239Np, as this is formed by the a decay of 243Am. We have measured the absolute intensity of the y line of 239Np (Ey = 277.6 keV)by means of an a particle calibrated 243Am source and the 293Hg source from the OSGI set of standard radioactive sources. The 243Am was calibrated in precisely known geometry from the a-particle counting rate provided by a silicon detector [1]? The y rays from the 243Ain and 293Hg preparations were recorded with a germanium detector having a sensitive volume of about 35 cm3. The absolute yield of the y line of 239Np (JyNp) was determined from NyNpQHgEviig YNP NvHgQAm6VND where NyNp and Nytig are the count rates produced by y rays of energy 277.6 for 243AM and 279.1 keV for 293Hg; QAm and Qllg are activities of those isotopes; el,Np, eyHe are the efficiencies for y rays of energies 277.6 and 279.1 key, respectively, in the germanium defector; and JyHg is the branching ratio for the y line (Ey = 291.1 keV) in the decay of 293Hg (0.8155 ? 0.0015 [21). The ratio of the y-ray efficiencies (e.yrig/eyNp) is dependent on the slope of the efficiency curve for y rays in the total-absorption peak. The trend with energy is governed by the size of the sensitive volume and the counting geometry. The ratio of the efficiencies for y rays of energies of 279.1 and 277.6 keV was mea- sured with the OSGI set as 0.995 ?0.004. We give below the components of the error that determine the overall error in measuring the branching ratio of the y line of 239Np having Ey = 277.6 keV, %; Statistical error Activity of 293Hg [3] Activity of 243Am [1] of 20311g Ratio of efficiencies for y rays and 243Am. Self-absorption of the y.rays in 243Am Branching ratio for y line of 293Hg (E =279.1 keV) Total error of measurement for the branching ratio for the y line of 239Np (Ey = 277.6 keV) 0.40 1.50 0.33 0.40 0.001 0.20 1.65 The overall error of measurement is clearly governed by the error in the calibrated 293Hg source from the OSGI set. We give below the branching ratios for the y line of 239Np with Ey = 277.6 keV as measured here and quoted elsewhere: Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 55-56, July, 1979. Original article sub- mitted September 1, 1978. 566 0038-531X/79/4701-0566807.50 0 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 f4] 0.145 ?0.004 [2] 0.1450 ?0.0015 [5] 0.141 ?0.004 [6] 0.152 ?1.005 Our result 0.1430 ?0.0024 We are indebted to S. E. Lavrov and V. I. Ivanov for preparing the 243Am source and determining the isotope composition. LITERATURE CITED 1. V. A. Dulin and V. K. Mozhaev, At. Energ., 44, No. 6, 528 (1978). 2. C. Bowman, Reports US Nuclear Data Committee, USNDC-9 (1973), p. 225. 3. Certificate Nos. 227 and 228, OSGI (1975). ? 4. J. Ahmad and M. Walalgren, Nucl. Lnstrum. Methods, 99, No. 2, 333 (1972). 5. L. N. Yurova et al., At. Energ., 36, No. 1, 51 (1974). 6. C. Bowman, Reports US Nuclear Data Committee, USNDC-11 (1974), p. 274. CALCULATION OF THE TRUE VOLUME PROPORTION OF STEAM IN THE DRIVING SECTION OF A NATURAL- CIRCULATION LOOP L. N. Polyanin and A. L. Putov UDC 621.039.52,44 Here we calculate the true volume proportion of steam in the driving section of a natural-convection loop operating at low pressures. The true volume content of steam cp is related to the mass flow X and the steam breakthrough factor w (p=1/(1 (,) ? p" ? 1 X -- X p' ) (1) where (3' and p" are the densities of water and steam, respectively. The coefficient co = Wv/Ww appearing in (1) varies over the height of the driving section, where Ww and Wv are the true speeds of the wa- ter and steam, on account of increase in the group rate of rise of the steam bubbles Wffs as the steam content increases. By definition Wv war w gy = + !is 1 ? (I) ris Ww Ww ' 1?x wsls ' (2) where Wods =G/piSds is the circulation rate, Scis is the area of cross section of the driving section, and G is the mass flow rate upon the heat carrier in the driving section. Measurements [1, 2] for (i9 :5_ 0.5 show that Wgrrs is related to the rate of rise of a single bubble W5 by (3) We substitute (3) into (2) to get WgrW?. ?(p) is ns = (1+ Kw) (1? P" )q /[1?(1?Kw ?r) P (4) where Kw = wksiwods. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 56-57, July, 1979. Original article submitted September 1, 1978; revision submitted November 10, 1978. 0038-531X/79/4701-0567$07.50 ?1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 567 where Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 co(40(z) 0,35 vo 425 0,2o qi5 ? 2 4 8 m Fig. 1. Height variation of co (z) calculated from (15) and the mean value Tp (z) for pressures (kgf/cm2) of: 1) 12; 2) 16; 3) 25; for X0 = 0.01. The variation of X overthe height z of the driving section is as follows for quasiequilibrium flow conditions: dX 1 di' 1 dp dz ? r dz ? r dp dz' dp dz = ?g (1 --(p) +-rcp], (5) (6) because the pressure loss due to4riction and acceleration of the flow can be neglected under these conditions. Here it is the enthalpy of the water on the saturation line, p is pressure, r is the latent heat of vaporization, and g is acceleration due to gravity. As dit/dp is comparatively small in the driving section, it can be taken as constant. where From (1) and (4)-(6) we get an equation for the true volume steam content: dz p' Dr----rp"jg (7). (9) The effect from boiling in the carrier (which causes co to rise in the driving section) is important only in the region of comparatively low pressures, where p"63' ? 1, andthen (7) has the solution =-1 17 1 -1- 2z / ? wo)2 D(4+ Kw) The value cp at the inlet to the driving section (z = 0) is given by o 1?X0 P" p To=1/[1+(l+Kw) ? ' X0 +Kw P" which is equivalent [1, 3] to the generally accepted formula 'Po = WO.I(WO+ W+ a), (9) (10) where W0t and W0" are the reduced velocities of the water and steam respectively, while a is the character- istic velocity of single-bubble rise \Vris appearing in (3). It is recommended [1, 4] that this speed should be derived from 568 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 a= {(0,65-0,0039p)63-- , d ds 200 mm, (12) where dds is the diameter ofthe driving section in mm and p is pressure in kgf/cm2 (11 :s p Is 125 kgf/cm2). It has been found by experiment [5] that the deformation of the steam-content curve at the inlet to the driving section has virtually no effect on the mean value and therefore on the flow rate of the carrier in this natural-circulation loop. Measurements on the VK-50 boiling-water reactor [6] provided an analogous conclusion, namely that the total flow rate in the natural-circulation loop is independent of the energy genera- tion in the individual cassettes in the core. Therefore, (p0 can be calculated from (10) with X0 taken as the mean mass steam content over the section at the outlet from the core. Figure 1 illustrates the solution by reference to theoretical cp (z, p) and p (z, p) = f co (zt, p)dzt for the case X0 = 0.01 and Kw =2; clearly, the change in the true volume content of steam oveP the height aris- ing from the boiling in the carrier is considerable at low pressures in an extended driving section, and this should therefore be incorporated into the calculations on the driving head and the steam available in the loop. LITERATURE CITED 1. A. I. Filimonov et al., Teploenergetika., No. 10, 22 (1957). 2. G. B. Wallis, One-Dimensional Two-Phase Flow, McGraw-Hill (1969). 3. A. Ya. Kramerov and Ya. V. Shevelev, Engineering Calculations on Nuclear Reactors [in Russian], Atomizdat, Moscow (1964). 4. G. G. Bartolomei, V. A. Suvorov, and S. A. Tevlin, in: Water Preparation and Processes in Boilers [in Russian], No. 1, Gosenergoizdat, Moscow (1963). 5. I. S. Dubrovskii, Teploenergetika, No. 2, 31 (1974). 6. A. P. Sarygin etal.,At. Energ. , 30, No. 4, 350 (1971). A LOCAL APPROACH TO DETERMINATION OF THE COORDINATES OF AN INTERFACE F. L. Gerchikov and V. D. Kosarev UDC 539.171:539.12 X rays are used to considerable advantage at the present time in automatic-control systems [1]; this requires an optimum apparatus design and also definition of the working conditions in the radiation fields, so it is necessary to know the parameters of the direct beam and of the scattered radiation, including the fields arising from backscattering at interfaces with air. Much of the information on scattered-radiation characteristics for interfaces has been derived either by Monte Carlo techniques or by integrating the distributions for point unidirectional sources over the surface of the scatterer or over the volume of the air [2-4]. However, the methods and apparatus available for integral evaluation of the scattered radiation and for determining the coordinates of the interface when one of the media is air are subject to substantial limitations on account of the marked effect of the component scattered by the air [2, 3]. Measurements show that the backscattered flux decreases away from the scatterer, whereas the flux scattered by the air increases. These two fluxes become comparable at a certain distance. The point where the fluxes are equal is the critical value licr as regards determination of the upper limit to the boundary position. It has been pointed out [2] that the y rays from 137Cs show a detectable effect in the air at a distance of 10 m, while Rcr = 22 m; our measurements have also shown that Rel. =12-15 m for x rays of effective quan- tum energy 60 keV [4]. Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 57-58, July, 1979. Original article submitted December 4, 1978. 0038-531X/79/4701-0569$07.50 ? 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 569 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 4i, Interface Fig. 1. Working geometry. Therefore, on the whole, the integral approach to the identification of interfaces and the parameters of the backscattering pattern in the presence of air show marked effects from the distance to the interface, and these effects are extremely important in determining the upper limit to the coordinates of the interface. Consider an air medium at a distance R from a scatterer exposed to point isotropic pulsed x-ray source RS which is combined with a total-absorption detector in conditions of good geometry, in which an energy flux E0 is emitted into an angle (Fig. 1). We estimate the air component of the scattering on the assumption that the interface is a hemisphere at the center of which lie the detector and source, which are at a distance R1 in vacuum from the hemisphere. The backscattered energy flux is [2] as follows in the air?vacuum geom- etry: Ea (E1)= E0Ae111012nRf, where Ae is the energy albedo. We increase R1 by a certain amount AR and then have by analogy with (1) that Ea (R1-1- AR)= E0AeV,/2n (R14-AR)'. The energy flux backscattered by the air layer at a distance AR from the detector is Ea(AR)= Ea(Ri+ AR) ?4(E1)? If a layer AR of air is placed at a distance R from the source, a survey [2] indicates that the backscattered energy flux arising from the localized area of air as corrected for attenuation is Ea (AR) = E 0AeY 0 exp (-2?0R)[1?exp (? 2ttoAR)] (2nR2)-i. (1) (2) (3) The density of the energy flux backscattered by the material is affected by the attenuation of the primary beam tto and that of the scattered beam j., the result being [2] Er= exp [ ? (tto ?I) (2nR2)-2 (4) We use (3) and (4) with suitable steps to get E a (A R) exp (? 2itoAR) Er exp ? (pi ?go) El As ?0AR ?1 and (iii?tio)R ?1 in (5) for soft x rays, we put Ea (AR)2p0AR Er We determine Rer by equating (6) to 1 and allow AR to tend to zero (the localized air liolume is minimal). Then we have 570 (5) (6) Rcr=(11?t1o)-1. (7) Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Comparison of (7) withthe analogous expressionRcr= (3p0+ ?1)-1 of [2] shows that local estimates of the backscattered radiation and determination of the position of the interface when one of the media is air can allow one to identify the backscattering from the air and the material over a range of coordinates of the in- terface broaderthanthat for the integral method. 'Engineering implementation of the local-evaluation method can be provided by dynamic strobing of the detector; a narrow strobe it (SR) is used with a synchronized source to scan localized volumes of air in accordance with a set program, as well as the surface of the scat- terer in order to identify the quanta scattered by the material and the air. In experiments, At =10 nsec (AR =1.5 m), and the radiation sources were ones developed in ?col- laboration with I. P. Karpinskii et al. [5] and Kalinin Polytechnical Institute in Leningrad, which have been used in determining the coordinates of air-concrete interfaces for R ?80 m. The detector was a plastic scintillator (polystyrene containing P-terphenyl and POPOP) working with an FEU-87 [6]. LITERATURE CITED 1. Apparatus and Methods for X-Ray Analysis [in Russian], Nos.19-21, Mashinostroenie, Leningrad (1978). 2. B. P. Bulatov and N. F. Andryushin, Backscattered Gamma Radiation in Radiation Engineering [in Russian], Atomizdat, Moscow (1971), p. 201. 3. Radiation Technology, Issue 3, Papers from the All-Union Radiation Engineering Research Institute fin Russian], Atomizdat, Moscow (1969), p. 117. 4. F. L. Gerchikov, At. Energ., 40, No. 6, 487 (1976); 41, No. 6, 414 (1976). 5. I. D. Ivanov et al., in: Nuclear Instrumentation [in Russian], Nos. 34-35, Atomizdat, Moscow (1977), p. 126. .6. -A. P. Karmanova and E. E. Stepanov, in: Papers from the All-Union Instrumentation Research Insti- tute [in Russian],- Nos. 30-31 (1976), p. 69. 571 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 ANNIVERSARIES ACADEMICIAN PAVEL ALEKSEEVICH CHERENKOV (ON HIS 75th BIRTHDAY'ANNIVERSARY) E. I. Tamm and B. B. Govorkov e ? 11,11.11.;,.. ' 1 ? On July 28, 1979,Pavel Alekseevich Cherenkov, the eminent physicist-experimenter, whose name is associated with one of the most outstanding scientific discoveries of our time, was 75 years old. He greeted his anniversary full of creative plans, and his energy and enthusiasm areto be enviedbymany young scientists. During recent years, by the initiative of Pavel Alekseevich, many new, interesting, and promising investiga- tions have been initiated, covering broad problems of contemporary physics. These include questions of the structure of elementary particles and the investigation of new nuclear structures (hypernuclei) and, at first sight far removed from these questions, problems of the generation and utilization in different fields of sci- ence and technology of new forms of electromagnetic radiation, like the so-called synchrotron and undulatory radiation. This is far from a complete list of the problems, on the solution of which P. A. Cherenkov is now working, as Director of one of the most prominent laboratories of the P. N. Lebedev Institute of Physics of the Academy of Sciences of the USSR. The creative life of Pavel Alekseevich is associated with this Institute. In 1932 he became a graduate of the Institute of Physics of the Academy of Sciences (FIAN) and, on the initi- ative of S. I. Vavilov, he started to investigate the luminescence of solutions of uranium salts under the action of y radiation. These investigations also led Pavel Alekseevich to the discovery of a new, remarkably beauti- ful physical phenomenon. He discovered that y radiation creates a weak luminescence of the solution, which differs sharply from normal luminescence. In extremely time-consuming experiments, in which the method of photometry at the threshold of vision was used, Pavel Alekseevich studied certain characteristic features of the emission discovered by him. In the investigations the main traits of P. A. Cherenkov's nature were displayed ? enthusiasm, unusual tenacity in achieving the designated goal, ability to find the simplest solution to the problems arising, and the knack of paying attention to the "trifles" of the experiment. After 2 years it already had become clear that the fluorescence discovered had no relation with lumines- cence, its polarization was measured, and an increase of energy in the emission spectrum with a reduction of Translated from Atomnaya Energiya., Vol. 47, No. 1, pp. 59-60, July, 1979. 572 0038-531X/79/4701-0572$97.50 0 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 the wavelength of the primary Y quanta was discovered. This allowed S. I. Vavilov in 1934 to arrive at the conclusion that the new form of luminescence was related with the electrons formed in the solutions by the Compton scattering of,y radiation. For the next few years, Pavel Alekseevich studied experimentally all the fundamental characteristics of the new physical phenomenon, the nature of which was realized in 1936, after its theory was developed by I. E. Tamm and I. M. Frank. They showed that the luminescence discovered by P. A. Cherenkov is the emission of a charged particle, moving with a velocity exceeding the velocity of light in the substance. In 1936-1937, P. A. Cherenkov verified quantitatively the Tamm?Frank theory by measuring the characteristic angle of emission and its dependence on the refractive index of the medium, established the energy distribution in the emission spectrum, and the absolute brightness of the luminescence. These investigations brought P. A. Cherenkov world recognition. G. S. Landsberg called them the "decoration of Soviet physics." The new form of radiation is known now as "Cherenkov radiation." In 1946, after this work, P. A. Cherenkov, 5.1. Vavilov, E. I. Tamm, and I. M. Frank were honored with the State Prize of the Soviet Union. The discovery by P. A. Cherenkov, in addition to the enormous scientific interest, has a great practical importance. Thus, in high-energy physics the most outstanding experimental research conducted over the period of the last decades has proved to be possible only because of the use of methods for recording par- ticles based on the application of Cherenkov radiation, or as it is now customary to say, Cherenkov counters. Threshold and differential (gas) Cherenkov counters, shower Cherenkov spectrometers, various Cherenkov chambers ? all these are the instruments without which it is impossible now to describe the experimental phys- ics of elementary particles. The use of Cherenkov detectors in physics, astronomy, and other fresh fields of science has reached such scales that, without fear of being mistaken, it may be asserted that P. A. Cherenkov is now one of the world's most well-known physicists. In 1958 P. A. Cherenkov, L E. Tamm, and I. M. Frank were awarded the Nobel Prize for Physics "for the discovery and explanation of the Cherenkov effect." In the years of the Great Patriotic War, Pavel Alekseevich was occupied with the development of an instru- ment of military designation, based on the use of certain methods of nuclear physics. Since 1946, Pavel Alek- seevich participated in the development and construction of the first electron accelerators in the laboratory directed by V. I; Veksler. After his participation in work on the construction of a 250-MeV electron synchro- tron, Pavel Alekseevich, together with the team of authors, was awarded the State Prize of the Soviet Union. From 1959 Pavel Alekseevich directed the Laboratory of Photomeson Processes of FIAN, investigating the electromagnetic interactions of elementary particles. For a start, Pavel Alekseevich carried out fundamen- tal research of photon ? nucleoli interactions, in particular the photoscattering of the lightest nuclei at an energy of 250 MeV. After this work, -in 1977 P. A. Cherenkov with co-authors was honored for the third time with the State Prize of the Soviet Union. Pavel Alekseevich headed the work on the creation of the FIAN scientific group for the investigation of electromagnetic interactions, including the high-intensity "Pakhra" accelerator, operating at 1.3 GeV, and the modern measurement?recording center. Without waiting for the completion of construction of this com- plex, P. A. Cherenkov in the laboratory started to work on a study of high-energy electromagnetic processes, creating jointlywith the Institute of High-Energy Physics (IFVE) and the Erevan Institute of Physics (ErFI) the electron beam on the Serpukhov proton accelerator. P. A. Cherenkov was one of the first physicists who paid attention to the abundant possibilities opened up by the use of synchrotron radiation. Even in the 1950s synchrotron radiation was the principal proposed and appliectt method, -proposed by him together with Yu. M. Ado, for the storage of electrons and for the production of colliding electron?positron beams in synchrotrons. Subsequently, Pavel Alekseevich and authors addressed a paper in which the possibilities were considered of using synchrotron radiation in science and technology. Now, synchrotron radiation is being widely used everywhere where there are electron synchrotrons and storage devices, and in some countries sources of synchrotron radiation have been specially constructed. P. A. Cherenkov, with young colleagues, has done much for the theoretical and experimental study of undulatory radiation on the tmdulator, built by them for the first time and operating in the rectilinear gap of the "Pakhra" synchrotron. Pavel Alekseevich Cherenkov is widely known not only to the world scientific community. He devotes much effort and energy to the struggle for peace and to the expansion of scientific relations between the scientists of different countries. For many years he has been a Member of the Presidium of the Soviet Committee for 573 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 World Protection, a Member of the Soviet Committee for European Safety and Collaboration, and a partici- pant of the Pugwash movement of scientists. Pavel Alekseevich Cherenkov has been rewarded with two Orders of Lenin. two Orders of the Red Ban- ner, the Order of the "Badge of Honor," and medals of the Soviet Union. The high merits of P. A. Cherenkov have been marked also with orders of foreign countries. The friends and colleagues of Pavel Alekseevich warmly wish him good health, success, and new crea- tive happiness. THE 50th BIRTHDAY ANNIVERSARY OF EVGENII VLADIMIROVICH KULOV The editorial staff of the Journal heartily congratulate Evgenii Vladimirovich Kulov, Member of the Editorial Board of the Head of the Central Administration of the State Committee for the Utilization of Atomic Energy, on his 50th birthday, and wish him good health and new creative successes. Translated from Atomnaya Energiya, Vol. 47, No. 1, p. 60, July, 1979. 574 0038-531X/ 79/4701-057007.5001980 Plenum Publishing Corporation Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 Declassified and Approved For Release 2013/02/15: CIA-RDP10-02196R000800020001-4 INFORMATION THE ACCIDENT AT THE THREE MILE ISLAND NUCLEAR POWER PLANT As is known, on March 28, 1979, there was an accident at the Three Mile Island nuclear power plant which attracted the close attention of the world for several days. At that power station there is a Babcock and Wilcox pressurized water reactor with a power of 956 MW (gross). The reactor was first brought to criticality on March 9, 1978, and produced its first electricity on March 15, and was in commercial opera- tion since December 30. There were many sensational and contradictory reports about the accident. In some of them the danger of the accident was unjustifiably exaggerated. Recently publications have appeared which are used as the basis of this report.* It makes it possible to follow the causes, development, and resolution of the accident and to evaluate its consequences. Chronology of the Development and Resolution of the Accident 0 sec (4:00:0 local time). At a power of 98% of nominal, all three feed pumps shut off. The cause of the shutting off was said to be either a cutting off of the supply of condensate to the condensate cleaning sys- tem due to a fault in a valve on a connecting pipe or an obstruction in the ion exchange filters. Similar shut- offs of the feed pumps had been noticed previously (at least eight times since October, 1978). When the main feed water system fails the emergency supply system is supposed to be turned on automatically. However, this time, although the emergency feed pumps were turned on, water did not come into the loop since the gates in this system had been left closed after earlier teats. As a result, the steam generators ceased to be supplied with feed water which caused the turbines to be shut off. According to a statement by the NRC, operation of a nuclear power plant with closed gates on the emergency feed water supply system is forbidden. 3-6 sec. Because heat removal had ceased the temperature and pressure in the reactor began to rise. At a pressure of 158 kg/ cm2 in the primary loop the relief valve 7 (see Fig. 1) on the volume compensator 8 operated and part of the coolant went into the overflow tank 3. 9-12 sec. When the pressure in the loop reached 166 kg/ cm2 the reactor was automatically stopped. 15 sec. The pressure in the loop fell to 155 kg/ cm2 and reached roughly an atmosphere below the value at which valve 7 should close; however, this did not occur. Evidently, the operators did not know that the valve had not closed since at that time the apparatus which indicated the water level in the volume compensator was out of order and gave high readings (the apparatus went off scale). 30 sec. Sensors indicated that the emergency feed water supply pumps were working but fruitlessly since, as noted, the gates in this system were closed. 60 sec. The water level in the volume compensator 8 rose sharply and reached a minimum in both steam generators. 2 min. When the pressure in the loop fell to 112 kg/ cm2 the emergency core cooling system (ECCS) turned on automatically, sending water directly into the primary loop. It is intended to operate as well if the water level in the volume compensator is reduced or the pressure in the containment vessel rises. 3 min. The pressure in the overflow tank 3 reached 7 kg/ cm'. 4 min 30 sec. Since the ECCS supplied more water than had flowed out of the volume compensator, the operator manually turned off one of the pumps supplying water to this system in order to avoid completely fil- ling the volume compensator, at which time it would become impossible (under normal conditions) to regulate the pressure in the primary loop. *This report is compiled from material published in: Nuclear Engineering International, 24, No. 285, p. 10, (1979); RUN-Actualites, No. 2, p. 190 (1979); Nuclear News, Special Report, April 6, 1979; Atomwirtschaft, 24, No. 5, p. 222 (1979); and SVA-Bulletin, No. 7, p. 11 (1979). Translated from Atomnaya Energiya, Vol. 47, No. 1, pp. 61-63, July, 1979. 0038-531X/ 79/ 4701-0575$07.50 Co 1980 Plenum Publishing Corporation Declassified and Approved For Release 2013