Preliminary results of a fuel-coolant interaction experiment in simulated molten fuel pool

Cheng, S.; Matsuba, Kenichi  ; Isozaki, Mikio; Kamiyama, Kenji  ; Suzuki, Toru; Tobita, Yoshiharu

In the severe accident analyses for sodium-cooled fast reactors, there is the possibility that a whole-core-scale pool containing sufficient fuel to exceed prompt criticality by fuel compaction might be formed. Local fuel-coolant interaction in the pool is regarded as one of the probable initiators that could lead to such compactive fluid motions. To clarify the mechanisms underlying this interaction, an experimental system using simulant materials has been developed. The experiments were conducted by delivering a given quantity of water into a simulated molten fuel pool. Current paper presents the experimental design and knowledge from preliminary analyses of several typical runs (with water quantity varying from 5 cc to 40 cc). Interaction characteristics including the pressure-buildup as well as mechanical energy release and its conversion efficiency are evaluated and compared in detail. It is revealed that as water quantity increases, a limited pressurization and resultant mechanical energy release is observable.