Yonggwang 4 power ascension test evaluation report on turbine load rejection test

The turbine load rejection event can be caused by a loss of external electric load, that is, a loss of offsite power or a loss of electric power flow path to the transmission system. The turbine load rejection tests at 50 % and 100 % power for Yonggwang Nuclear Power Plant Unit 4 (YGN 4) were performed to demonstrate that the NSSS and turbine-generator systems can accommodate the load rejections by controlling operating parameter within the acceptable ranges, without causing reactor and turbine trip, and without opening primary and/or secondary safety valves. In this report, the measured plant operating parameters were compared against the expected values and the results predicted by LTC computer code to verify the plant design as well as to validate the computer code. From this evaluation, it is concluded that the control systems of YGN 4 properly responded to accommodate the events by performing its own functions during these tests and hence the turbine load rejection tests at 50 % and 100 % power were successfully performed meeting the test acceptance criteria. 8 tabs., 68 figs., 6 refs. (Author) .new