ATWS analysis for Maanshan PWR using TRACE/SNAP code

• To calculate overpressure phenomena for a PWR under ATWS.
• A review for AMSAC system that built for Westinghouse PWR.
• Feedback to U.S. NRC for developing TRACE code.
• Restriction on MTC that demanded by Taiwan Power Company.
• Sensitivity studies on RCP trip, and partial failure of MDAFW.

The objective of this study was to use TRACE code to analyze the reactor coolant system pressure transients under LONF ATWS for Maanshan PWR. According to Westinghouse Anticipated Transients Without Trip report, LONF ATWS was considered as the most severe plant condition. The ASME Code Level C service limit criteria of 22.06 MPa (3200 psig) was assumed to be an unacceptable plant condition in SECY-83-293. In accordance with 10 CFR 50.62, Maanshan NPP has established AMSAC. Unlike the reactor trip system, it automatically initiates the auxiliary feedwater system and turbine trip under conditions indicating an ATWS. Since the ATWS analysis is not specified in the FSAR (Taiwan Power Company, 1982), TRACE code was used to assess the RCS pressure for Maanshan NPP. Analysis results indicate that RCS pressure can be maintained within 22.06 MPa with sufficient negative moderator temperature coefficient and normal work of AMSAC and valves.