Accident analysis for test pin failure during Power-to-Melt test

Morii, Tadashi*; Kinjo, Hidehito*

Effects of pin failure during Power-to-Melt test performed in the experimental fast reactor "JOYO" have been analyzed in the present study in order to obtain a license for the test. The accident scenario of the present study is that after a clad failure of a test pin, melted fuel is released and forms blockage of fuel and stainless steel debris in a coolant flow area of a compartment in the test assembly. The follwing subjects have been investigated in the present study. (1)Blockage in the coolant flow area. (2)Contact of melted fuel with compartment. Conclusions are summarized as follows. (1)Under a hypothetical assumption in which all 4 test pins are melted and form a blockage, if the outer surface of the compartment is cooled by Na flow of an about 2200kg/(ms), the integrity of the compartment is assured. (2)If melted fuel released from the test pin directly come in contact with the inner surface of the compartment, the calculated results show that the fuel can not melt through the compartment.