"JOYO" Special test report; In-core flow rate distribution measurement test of the irradiation core equilibrium cycle

not registered; not registered; Fukami, Akihiro*; not registered; not registered

In-core flow rate distribution measurement test is conducted after the seventh duty cycle of experimental fast reactor "JOYO" irradiation core (MK-II core). The high flow rate test (90% flow rate) and the low flow rate test (20% flow rate) are conducted, which are the same as previous tests. Furthermore, the very low flow rate test (6% flow rate) and also the test at pump-stop condition are newly conducted. The test results are as followings. (1)It is confirmed that the analysis eode which is used for the core management is verified with satisfactory accuracy. (2)In the case of the test at pump-stop condition, it is measured that the flow rate of the fuel subassembly is proportional to each subassembly's decay heat. (3)It is found that the ratio of center fuel subassembly flow rate to the total fuel flow rate at the 6% flow rate test is smaller than the ratio at the 90% flow rate test. (4)The fuel subassembly flow rate slightly decreased by the lapse of time after loading in the core. The decreasing ratio to the burn-up is -8.53 10/MW D/T and the ratio to the lapse day in the core is -2.12 10/day.