HEAT REMOVAL TESTS FOR THE HIGH PERFORMANCE VAULT STORAGE SYSTEM OF SPENT NUCLEAR FUEL

A new concept has been proposed for a vault type spent fuel storage system which can achieve a high storage density of 0.7MTU/m 2 . Two canisters, with 10 - 40 BWR spent fuel assemblies each, are vertically inserted in line into a storage tube. The storage room is radiologically shielded and an air flow separation baffle is installed horizontally in the middle of the area holding the storage tubes. The cross flow air generated by the stack effect removes decay heat from the spent fuel. Heat removability in the storage room is one of the most important points for realizing this system. Small model tests and thermal hydraulic analysis were performed to clarify the air flow distribution in the storage room. Air flow rate and pitch distance of heaters were chosen as experimental parameters. The analysis model was confirmed by test data. The analysis model and knowledge acquired from the heat removal tests were applied to improve the air flow passage in the storage room so that the structural concrete temperature remains below 65 oC during the storage period and the pitch distance of the storage tubes can be rationalized to increase the storage density.