THERMAL-HYDRAULIC EVALUATION OF JOYO FUEL SUBASSEMBLY WITH LOCAL BLOCKAGE

摘要

In the incident of the experimental fast reactor Joyo in June 2007, little amount of metal powder was estimated to be produced by the contact between the bottom of the upper core structure and the test section of the material testing rig with temperature control. Up to now, no foreign materials were detected by the in-vessel observations. However, a small amount of metal powder which could be placed into the fuel pin bundles was assumed in the present study. Preliminary safety evaluation of the wire-wrapped fuel pin bundles of Joyo with local blockage were performed in the rated power operational condition, an anticipated transient during operation and an accident. A single-phase transient subchannel analysis code ASFRE, which was verified by various local blockage experiments in France and in Japan, was applied to the present evaluations. From these results, it was concluded a small amount of metal powder assumed to be produced by the incident would not affect the safety operations in rated power conditions, in anticipated transients and in accidents.