Simulation of Reactor Power Cutback System Tests for YGN 3 and 4

Abstract

Among those tests performed during the Yonggwang Nuclear Power Plant Units 3 and 4 (YGN 3 and 4) Power Ascension Test period, the 'Load Rejection to House Load' and 'Loss of One Main Feedwater Pump' tests at 100% power are the major tests in which the Reactor Power Cutback System (RPCS) plays a key role for a successful execution. Unless the NSSS control systems including RPCS actuate properly, the reactor will be tripped on low SG water level or high pressurizer pressure. The tests performed for both units 3 and 4 were successful by meeting all acceptance criteria, and the plant was stabilized at a reduced power level without reactor trip mainly due to a proper RPCS actuation. The measured test data for the major plant parameters are compared with the predictions made by the KISPAC computer code, a best-estimate plant performance analysis code, to verify and validate its applicability. The comparison results showed good agreement in the magnitude as well as the trends of the major plant parameters. Therefore, the KISPAC code can be utilized for the best-estimate nuclear power plant design and simulation tool.