Preliminary criticality safety evaluation of long-term storage of spent nuclear fuels

Okuno, Hiroshi; Suyama, Kenya; Okuda, Yasuhisa*; Yoshiyama, Hiroshi*; Miyoshi, Yoshinori

Proceedings of 8th International Conference on Nuclear Criticality Safety (ICNC 2007), p.140 - 143, 2007/05

In this research, a preliminary critical safe evaluation of a canister was performed, which stored either (1) four UO fuel assemblies (initial uranium enrichment of 4.1 wt%) or (2) four mixed uranium and plutonium oxide (MOX) fuel assemblies (initial plutonium enrichment of 10 wt%) for pressurized-water reactors (PWRs) in the earth for 1000 years without a crash of a fuel bundle. Ten actinide nuclides were chosen, most of which based on "A Guide Introducing Burnup Credit, Preliminary Version", and their compositions were computed with the SWAT code system. Criticality calculations were carried out with the MVP code adopting the computed composition, and the neutron multiplication factor was calculated to be less than 0.9. Issues for consideration were finally summarized.

Benchmark analyses of criticality calculation codes based on the evaluated dissolver-type criticality experiment systems

Okuno, Hiroshi; Takada, Tomoyuki; Yoshiyama, Hiroshi; Miyoshi, Yoshinori

JAEA-Data/Code 2005-001, 117 Pages, 2005/11

JAEA-Data-Code-2005-001.pdf:9.37MB

Criticality calculation codes/code systems MCNP, MVP, SCALE and JACS, which are currently typically used in Japan for nuclear criticality safety evaluation, were benchmarked for so called dissolver-typed systems, i.e., fuel rod arrays immersed in fuel solution. The benchmark analyses were made for the evaluated critical experiments published in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook: one evaluation representing five critical configurations from heterogeneous core of low-enriched uranium dioxides at the Japan Atomic Energy Research Institute and two evaluations representing 16 critical configurations from heterogeneous core of mixed uranium and plutonium dioxides (MOXs) at the Battelle Pacific Northwest Laboratories of the U.S.A.. The results of the analyses showed that the minimum values of the neutron multiplication factor obtained with MCNP, MVP, SCALE and JACS were 0.993, 0.990, 0.993, 0.972, respectively, which values are from 2% to 4% larger than the maximum permissible multiplication factor of 0.95.