Study for subassembly porous blockage in fast breeder reactors; Pre-subchannel analysis of 37-pin bundle sodium test

Iitsuka, Toru; Oki, Yoshihisa; Kawashima, Shigeyo*; Nishimura, Motohiko; Isozaki, Tadashi; Kamide, Hideki 

Assessment of the maximum temperature and the position of the hot spot is the most important issues on the reactor safety when the local subchannel porous blockage is occurred. From these background, authors are going to perform a sodium experiment with 37-pin bundle test rig simulating the porous blockage, to understand the phenomena and acquire data for thermal-hydraulic analysis code validation. Before the execution of sodium test, one basic experiment and some using subchannel analysis code ASFRE-III had been done. The basic experiment was a water test to examine the pressure loss characteristics of the porous blockage. The pressure loss correlation derived from the water test was applied to the subsequent subchannel analysis of the 37-pin bundle sodium test rig. The analysis such predicted that the difference between the maximum temperature and the inlet temperature would be in propotion to the power to flow rate ratio, within the condition of the power=100400 W/cm and the flow rate =200480 /min. And it was also shown that the maximum subchannel temperature would not over the operational limit temperature 650 C, if the power to flow rate ratio were kept lower than 0.75(W/cm)//min). The map was made to predict the maximum temperature from the experimental conditions.