Analysis of Multiple Steam Generator Tube Rupture for AP1000

The multiple steam generator tube rupture accident in AP1000 was analyzed using RELAP5/MOD3 code. Based on best-estimated method, 1.5 steam generator tube rupture cases were analyzed. The results show that the main steam safety valve (MSSV) remains closed with power-operated relief valves available and the containment bypass will not occur. In each case, there is no core makeup tank level reduction and no automatic depressurization signal generated. Even if MSSV is postulated to stick open, the core is never uncovered and remains cooled.