The software for Level 1

2 and 3 probabilistic safety assessments (PSA) was developed based on the PSA code by the US Nuclear Regulatory Commission and independent research.It was applied to integrating the design of a 300 MW nuclear power plant

unit 2 (C-2).It includes the analysis of initiating events

event trees

fault trees

dependency analysis

human reliability analysis

database analysis

event sequence quantification

plant damage state analysis

accident progression and containment response analysis

source term analysis

large early release frequency (LERF) analysis

uncertainty analysis

importance/sensitivity analysis

applications during design phase

etc.The model of Level 1 and 2 PSA was established for the C-2 unit.Several design improvements based on the PSA were implemented in the design

such as the isolation valves on the mini-flow line of the safety injection pump and spray pump

reciprocating charging pump in chemical and volume control system

essential service water system

etc.The unit’s internal events at power generation were assessed as 7.25×10-6/ry for core damage frequency (CDF) and 3.24×10-7/ry for LERF.The C-2 PSA has not only justified the balance of its design

but also provided the probability assessment information for optimizing C-2 design and operation strategies

reducing the risk of severe accidents efficiently.