The challenges of licensing the AP600 passive nuclear power plant design

Westinghouse recently received a final design approval from the United States Nuclear Regulatory Commission for the AP600, a simplified passive advanced light water reactor (ALWR) nuclear power plant of 600 MWe national output power rating. The AP600 passive safety systems provide the functions of safety injection, decay heat removal and containment cooling without any ac power, in contrast with the designs of traditional reactor designs. In addition, there are a number of systems in the AP600 that are nonsafety-related that are considered safety-related in current plant designs. The AP600 design approach, while based on proven technology, did not directly conform to all aspects of the pressurized water reactor design described in the Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants (NUREG-0800). Therefore, a significant effort was required on the part of Westinghouse to convince the Nuclear Regulatory Commission technical staff that the design would be safe to construct and operate as required by Title 10 of the Code of Federal Regulations. The most significant part of the AP600 review effort was the test and analysis program which obtained data under prototypical passive plant accident conditions to verify and validate the computer programs used to perform the safety analyses required in the Standard Safety Analysis Report. A unique approach was agreed to between the Industry and the NRC to determine what additional regulatory oversight was required for the nonsafety-related AP600 systems that were safety-related in currently operating plants. The agreed to combination of deterministic and probabilistic approaches was one of the first examples of risk informed regulation. This paper discusses the regulatory review process that led to the final design approval along with the technical and regulatory advances that were approved over the course of the AP600 review. (author)