TRACE/PARCS coupling model of Lungmen NPP has been used to analyze the full isolation startup test, defined as a simultaneous full closure of all MSIVs (Main Steamline Isolation Valve). In this analysis, the full closure time of MSIVs was varied by 2 sec, 3sec (base), and 4 sec. As MSIV was closed to 90% full open position, a reactor power scram signal was initiated. For each of MSIV full closure time, the delayed time of scram signal to the start of control rod insertion was varied by base 0.09 sec, 0.04 sec, and 0.14 sec. Because of MSIVs closure, the increasing reactor dome pressure reached the setpoint of relief valves (RVs) and caused RVs to open. The 4 reactor internal pumps (RIPs) not connected to the M/G sets tripped and were runback to minimum pump speed when water level dropped to L3. The 6 RIPs connected to the M/G sets tripped if low water level (L2) or high reactor dome pressure (1140 psia) had been reached. Those important thermal parameters with various MSIV full closure times (2, 3, and 4sec) and various reactor scram signal delay times (0.09, 0.04, and 0.14 sec) are compared and shown in this paper.

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