Evolutionary design and construction: The system 80+TM solution to the cost-benefit dilemma

ABB Combustion Engineering Nuclear Power provides advanced nuclear power plant designs using an evolutionary design and implementation process. Since the emergence of severe accident concerns following the Three-Mile-Island accident, the industry has faced the problem of providing improved designs that are more economical to construct and operate relative to the current generation of operating nuclear power plants. It is easy to improve plant safety in the design process, but it is not so easy to develop features that are economical while at the same time improving safety. Moreover, it is critical to add only those design features that can be implemented in actual construction programs with high confidence that they will perform as expected. The key to ABB's development and implementation of advanced reactor designs is an evolutionary process that relies on use of proven design concepts and proven components. Furthermore, design improvements are implemented gradually in actual construction programs in order to maintain very high confidence that construction schedules will not be adversely affected and that plant startup and commercial operation will proceed as expected. ABB has demonstrated the success of the above approach through the System 80 design implemented at the Palo Verde Nuclear Generating Station, the gradually improved Korean Standard Nuclear Power Plant (KSNPP) designs (based on System 80) being constructed in the Republic of Korea, and the System 80+ Standard Plant Design certified by the US Nuclear Regulatory Commission (NRC) in 1997. This paper describes the improved redundancy, diversity, and simplicity of the more significant advanced design features that were included in the System 80+ design and that are now being implemented in the KSNPP and Korean Next Generation Reactor (KNGR) programs. Examples described herein include plant safety systems, control and electrical systems, and severe accident mitigation systems. Probabilistic Safety Analyses were performed to identify those design features with the most significant impact on plant safety as measured through core damage frequency, containment reliability, and off-site radiological releases. This paper presents improvements in core damage frequency for various initiating events and identifies the advanced design features, which contributed to the improvement. The radiological doses for System 80+ are presented and compared to those for plant designs typical of those analyzed when the current emergency planning regulations were being established. The results show significantly lower offsite doses to individuals at all distances from the plant and also a significant reduction in the land area for protection against radioactive foodstuff ingestion. (author)