HTGR Knowledge Base

Conference Article: Investigation of Criticality Parameters of High Temperature Reactors at the Kurchatov Institute’s ASTRA Critical Facility

Abstract

The basic parameters of critical assemblies created at the ASTRA critical facility of the RRC Kurchatov Institute for simulation of high-temperature reactors are given in the paper. Capability to simulate different HTGR reactors at the ASTRA critical facility is presented. Brief description of the experiments simulating the PBMR reactor being developed in Republic of South Africa is given. Spherical graphite elements with the outer diameter of 6 cm containing about 2.4 g of uranium with the enrichment of about 21 % are used as fuel elements at the facility. Fuel particles (kernels) made of uranium dioxide with the diameter of about 500 micrometers, having four-layer coating are evenly distributed in the graphite matrix in the central part (5 cm in diameter) of each spherical fuel element. Graphite blocks are used as moderator in reflectors. Up to 46000 spherical elements were loaded in the core in the most recent experiments. Anticipatory computations of critical parameters of the assemblies performed at the RRC KI for the substantiation of criticality safety of the experiments are described in the paper. The calculations were performed with the Russian MCU program complex, which uses Monte-Carlo method. The MCU code was modified for calculations of the double heterogeneity of the HTGR fuel. Kernels of coated fuel particles were not smeared with graphite matrix of fuel elements, and their heterogeneous structure was directly taken into account in the calculations. Results of the implemented experiments are intended for validation of calculational codes used in HTGR designing and justification of neutronics of HTGRs under development.

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Reference:

Proceedings of the Conference on High Temperature Reactors, Petten, NL, April 22-24, 2002
Organized by HTR-TN in cooperation with the European Nucler Society (ENS) and the IAEA

International Atomic Energy Agency, Vienna (Austria)

HTR-2002, pp:1-5