JOYO MK-III performance test report. Blower start-up test (PT-303), power-increase test (PT-301), rated power operation test (PT-302)

In the MK-III performance test for the experimental fast reactor JOYO, the reactor thermal power was raised gradually with steps at about 20%, 50%, 75%, 90%, and 100% (140 MWt). The rated power of 140 MWt for the MK-III reactor core was reached on October 28, 2003. Then, it was operated continuously by rated power for 100 hours or more. The major results of the tests are as follows. (1) From standby states (sodium temperature of 250degC, isothermal condition), the rated power of 140 MWt for the MK-III reactor core was reached on October 28, 2003 by the usual power-increase operation (a power-up rate of about 5 MWt/20 min, where the power was held for about 10 minutes every 5 MWt). It was confirmed that the temperature and flow of sodium were the alarm setting values or less at each steps. (2) The blower start-up operation of which the parameter was the reactor thermal power was done, and the influence which it was on coolant temperature was confirmed. As a result, the optimal reactor thermal power to start up the blower from a natural ventilation cooling state was set to about 18 MWt, and the starting procedure was made into a method (order of 1A->2A->1B->2B) which starts four sets of one blower at a time one by one. (3) The reactor shutdown operation was confirmed by two simultaneous control-rod insertions at 35 MWt. It was confirmed to be carried out by a series of operations from the control rod insertion to the blower shutdown with enough time margin. By adopting this reactor shutdown operation, operation complexity was mitigated and plant characteristics also improved. (4) The rated power of 140 MWt was reached on November 14. It was operated continuously by rated power for 100 hours or more on November 20, 10:30. The detailed plant data was acquired at intervals of 24 hours, and was confirmed to be less than the alarm setting values. (author)