A method for development of efficient 3D models for neutronic calculations of ASTRA critical facility using experimental
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thod for Development of Efficient 3D Models for Neutronic Calculations of ASTRA Critical Facility Using Experimental Information A. L. Balanina, V. F. Boyarinova, E. S. Glushkova, A. A. Zimina, G. V. Kompanietsa, V. A. Nevinitsaa*, N. P. Moroza, P. A. Fomichenkoa, A. V. Timoshinova, and Yu. N. Volkovb a National b
Research Center Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 Russia National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409 Russia *e-mail: [email protected] Received March 12, 2015
Abstract—The application of experimental information on measured axial distributions of fission reaction rates for development of 3D numerical models of the ASTRA critical facility taking into account azimuthal asymmetry of the assembly simulating a HTGR with annular core is substantiated. Owing to the presence of the bottom reflector and the absence of the top reflector, the application of 2D models based on experimentally determined buckling is impossible for calculation of critical assemblies of the ASTRA facility; therefore, an alternative approach based on the application of the extrapolated assembly height is proposed. This approach is exemplified by the numerical analysis of experiments on measurement of efficiency of control rods mockups and protection system (CPS). Keywords: HTGR, ASTRA critical facility, axial distribution of reaction rates, buckling, 3D numerical models DOI: 10.1134/S1063778816080032
The modern state of the art in software and computers for neutronic calculations allows adequate 3D simulation; however, effective 2D models are sometimes used in practice of reactor calculations (in particular, for verification); in these models, the vertical dimension is taken into account using axial buckling (see, for example, [1]). As a rule, this parameter is determined using experimental data on axial distributions of fission and capture reaction rates. The practice of calculation of experimental configurations assembled at the ASTRA critical facility for investigation of high temperature reactor physics demonstrated that in some cases it is more correct to use experimental information on axial distributions of fission and/or capture reaction rates for development of 3D, rather than 2D, numerical models [2]. Experimental studies at the ASTRA critical facility cover the following problems: (i) experimental simulation of energy release fields (measurement of fission reaction rate distributions); (ii) measurement of CPS efficiency and their interference coefficients, determination of calibration characteristics of control rods; (iii) measurement of the neutron kinetics parameters;
(iv) experimental simulation of the physical startup of a reactor. Reactors of HTGR type simulated at the critical facility have the following specific features influencing their neutronic characteristics: (i) fuel in the form of particles with multilayer coating placed in a graphite matrix of fuel elements; this design results in double heterogeneity of fuel arrangement in the core and require
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