Abstracts and Available Papers Presented at the
1998 International RERTR Meeting

NEUTRONICS CHARACTERISTICS OF JRR-4 LOW ENRICHED URANIUM CORE

Yoshihiro NAKANO, Yoshiro FUNAYAMA and Teruo NAKAJIMA

Japan Atomic Energy Research Institute
Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 Japan

ABSTRACT

JRR-4 (Japan Research Reactor No.4) had been operated using 93% enriched uranium (HEU) fuel since 1965. All of fresh HEU fuels had been consumed and stopped the reactor operation on January 1996. The reactor modification works started not only for fuel conversion but also for installation of a medical irradiation facility, repairing of the reactor building and so on. It has finished June 1998 and performance tests have begun. JRR-4 achieved the first criticality using 20% enriched uranium (LEU) fuel on July 14th, 1998. The minimum critical core consisted of 12 fuel elements, reflector elements and other reactor elements. During the tests, several reactor physics parameters have been measured. This paper presents the results of the tests. Methodology and results of neutronics design calculations are presented as well. The results are compared with the measured data.

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