Development of a National Neutron Database for Nuclear Technology
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- 7 - XA9744992 DEVELOPMENT OF A NATIONAL NEUTRON DATABASE FOR NUCLEAR TECHNOLOGY A. V. Ignatyuk, V.N. Kononov, B.D. Kuzminov, V.N. Manokhin M.N. Nikolaev, B.I. Furzov State Research Centre of the Russian Federation Institute of Physics and Power Engineering, Obninsk Abstract This paper describes the stages of a many years activities at the IPPE consisting of the measurement, theoretical description and evaluation of neutron data, and of the establishment of a national data bank of neutron data for nuclear technology. A list of libraries which are stored at the Nuclear Data Centre is given. Introduction Currently, nuclear technology has found wide applications in a number of fields in science and technology consisting of: - nuclear energy (nuclear fission reactors, nuclear fission reactors, radioisotopic sources) - nuclear transmutation (production of radioisotopes for medical and other applications, burn-up of long-lived radio nuclides, radiation alloying of semiconducting materials, etc..) - nuclear instrumentation in industry (activation analysis, nuclear micro-analysis, control of fissile materials, etc..) - scientific investigations (nuclear physics, nuclear astrophysics, medicine, radiobiology, agro-radiology, ecology, etc.). In the sphere of nuclear technology, a number of processes use more than 500 stable and radioactive nuclides in a broad energy range. To ascertain the proper functioning of nuclear installations which have various functions and applications in industrial projects and scientific investigations, there is a need for nuclear data that characterize the properties of nuclear reactions. The reliability of radiation and nuclear safety, the ecological acceptance, and the economical planning of nuclear installations, all depend on the completeness, quality and accuracy of nuclear data. To satisfy that need, a concerted effort spanning many years of research in the field of neutron data at the FEI and other research institutes have led to the - 8 - creation of the National Library of Recommended Evaluated Data, BROND. This systematically planned research effort consisted of the following activities - the determination of the main requirements and optimal accuracies of the nuclear data, - the measurement of cross sections and other parameters which characterize the interaction of neutrons with fissile, structural and technological materials, the minor actinides and fission products, - experimental and theoretical research to determine the mechanisms of nuclear reactions needed for the development of models used to ensure the required accuracy of calculational results; - the development of evaluation methods and the evaluation of neutron data including all results obtained from experimental measurements and theoretical calculations, - the creation of a domestic system of files of recommended evaluated neutron data, and their storage in computer data banks, and the satisfaction of users' requests The data survey includes data published since 1972 until now in accordance with State projects (established in accordance with the Council of Ministers decree No. 474-163, dated 15.06.1976. Listing of federal goal-oriented programs, P. 11 - Scientific and technological programs) and specialized programs (in accordance with decrees No. 0156 dated 30.06.71; No. 086 dated 22.04.82, No. 0187 dated 23.07.76 and No. 770 dated 10.10.88, of the long- term Russian research program in the field of nuclear data for the years 1995-2005). Goal-oriented research which would have the objective to guarantee the availability of neutron data to problems related to the following fields of activities: - fast and intermediate neutron power reactors; - nuclear safety and internal reactor safety; - external fuel cycle; - ecologically safe handling of long-lived radioactive waste (burial and transmutation); - radiation resistant materials; - disassembly of used up reactors: - usage of weapons and reactor plutonium; - development of the international fusion reactor project; - manufacturing of radioisotopes for medical application, diagnostics and therapeutics; - radiation protection of defense oriented problems; - geophysical, astrophysical and a number of other applied problems in the national economy. The research was executed primarily by the staff of the Institute of Physics and Power Engineering (FEI). Some of the work was performed by scientists of other Russian institutes, namely: - the Russian Federal Nuclear Centre - VNIIEF - the Radium Institute - RI - the Russian Science Centre - Kurchatov Institute - the State Science Centre - NIIAR - the Institutes of the Russian Academy of Sciences - 9 - - NIYaFS (S Petersburg) - Iyal (Moscow) and others; - the Institute of Nuclear Research of the Ukrainian Academy of Sciences - Iyal UAN - the Institute of Nuclear Energy of the Byeloruss Academy of Sciences - IAE BAN, and currently, - the Institute of Radiation Physical Chemistry - IRKhFP The coordination of the research was executed by the Russian Commission on Nuclear Data and the FEI institute The considerable demand for a high quality of needed neutron data, the enormous number of stable and radioactive nuclides which are involved in nuclear technology, and the wide energy range of the interactive particles (which at the present time extends from fractions of electron volts (eV) to a few GeV) has inevitably led to international cooperation so as to be able to cope with the solution of nuclear data problems. I. Structure of the Nuclear Data Activities The generation of nuclear data, which is a complex scientific activity, requires the participation of highly qualified staff and the availability of highly precise instrumentation. Neutron data exists in a variety of forms: - differential experimental neutron data which characterize nuclear interaction at a fundamental level, - reference or standard neutron data, which require extreme exactness and precision in their production, - theoretical data, resulting from calculational models, - integral neutron data which characterize the properties of a combination of nuclear interactions in various media or differential characteristics averaged over a broad energy range; - evaluated neutron data generated from a combination of experimental data and theoretical models of nuclear reactions; - task-dependent data. The principal objective of the generation of neutron data is the creation of a universal library of evaluated neutron data which could serve as the underlying source of information for the solution of specific nuclear technology tasks. Figure. 1 shows the interdependence of nuclear data activities Nuclear data users specify the accuracy requirements in the calculation of parameters or formalisms which characterize the properties of the projected nuclear installation. Based on these objective-oriented requirements, specialists formulate a list of needed neutron data and their required accuracy. At the initial stages of the project, when the viability of the project is being investigated, the accuracy of the nuclear data is not of great importance. At subsequent stages, however, when the conceptual aspects of the project are being investigated, and the safety and economical aspects come into play, much more accurate data are needed. Should the accuracy of the existing experimental and evaluated neutron data - 10 - not satisfy the stated requirements, a special program, designed to generate new data or improve the accuracy of the existing data, is then implemented. The measurement of differential neutron data are performed either to validate nuclear models, to merge the calculated results with the existing experimental data in order to improve their accuracy, or to create data for special applications. The results of differential neutron data measurements serve as the principle source of information in the generation of evaluated data. NUCLEAR DATA USERS NUCLEAR DATA REQUIREMENTS FINANCING RESEARCH PLAN DEVELOPMENT DIFFERENTIAL MEASUREMENTS INTEGRAL MEASUREMENTS EXPERIMENTAL DEVELOPMENT BANK OF DATA BANK OF THEORETICAL INTEGRAL MODELS EXPERIMENTS GENERATION CHECKING OF EVALUATED OF DATA FILES DATA FILES LIBRARY PROBLEM ORIENTED OF RECOMMENDED NUCLEAR DATA EVALUATED DATA INTERNATIONAL BANK OF EVALUATED DATA Figure 1. Structure of nuclear data activities - 11 - Currently, theoretical modeling of neutron interactions plays an important role in satisfying existing requirements of neutron data inasmuch as trying to satisfy the neutron data demand by means of their measurement alone is not practical because they cost too much and take too long to implement. Calculations using theoretical models give a realistic representation of the shape of the dependence, however, the values of calculated reaction cross sections are not accurate enough. In order to increase the accuracy of the calculational results, it is necessary to normalize the calculated curves to experimental data. Thus, theoretical and experimental results complement each other: theory generates the shape of continuous curves, and the measurements provide accurate values of the data At the same time data measurements yield a number of parameters (such as fission barrier characteristics, level densities, optical model parameters, and others), which enter into the theoretical model calculations. An enormous amount of experimental and theoretical data has accumulated over the years. However, before they can be used in nuclear technology projects these data must go through an evaluation stage During that stage, scientist collect all of the available