Compilation report of VHTRC temperature coefficient benchmark calculations

A calculational benchmark problem has been proposed by JAERI to an IAEA Coordinated Research Program, 'Verification of Safety Related Neutronic Calculation for Low-enriched Gas-cooled Reactors' to investigate the accuracy of calculation results obtained by using codes of the participating countries. This benchmark is made on the basis of assembly heating experiments at a pin-in block type critical assembly, VHTRC. Requested calculation items are the cell parameters, effective multiplication factor, temperature coefficient of reactivity, reaction rates, fission rate distribution, etc. Seven institutions from five countries have joined the benchmark works. Calculation results are summarized in this report with some remarks by the authors. Each institute analyzed the problem by applying the calculation code system which was prepared for the HTGR development of individual country. The values of the most important parameter, keff, by all institutes showed good agreement with each other and with the experimental ones within 1%. The temperature coefficient agreed within 13%. The values of several cell parameters calculated by several institutes did not agree with the other's ones. It will be necessary to check the calculation conditions again for getting better agreement. (J.P.N.)