JOYO Start-up test report; PT-41 Decay heat removal by main cooling system

Hirose, Tadashi*; Endo, Masayuki*; Nanashima, Takeshi*; not registered; not registered; Yamamoto, Hisashi*

The purposes of this test are to : (1)verify the procedure for decreasing reactor power from 50 MWt to shutdown, (2)remove the decay heat after shutdoun by the main heat-transport system using the normal procedure, (3)confirm that the rate of temperature decrease does not exceed -50C/hr during the cooldown. At the end of a full power (50MWt) run of 100hours, record steady state plant data. By insertion of one regulating rod, decrease reactor power until PRM indicates 80% (40MWt). Verify that a steady-state condition has been achieved (at least 15 minutes) and repeat data recording. Following same procedure, decrease power stepwise to 30 MWt, 20MWt and 10MWt. Stop the DHX Blowers at 10MWt. Decrease reactor power with one regulatiag rod to 1MWt as indicated on IRM, then shut down the reactor by slow scram. By manual operation of DHX vanes and dampers, decrease coolant temperature as rapidly as possible to the "warm standby" condition (The maximum allowable cooldown rate of 50C/hr must not be exceeded). Test results : (1)The main coolant temperature decrease rate averaged 34C/hr (maximum of 48C/hr) during the cooldown from full power to reator shutdown. During this period, the insertion rate of one regulating rod was approx. 1mm/minute. (2)The average rate of main coolant temperature decrease from shut down to "warm standby" was 35C/hr in manual control.