The light water reactor pressure vessel surveillance dosimetry improvement program (LWR-PV-SDIP): Past accomplishments, recent developments and future directions

The integrity of the pressure vessel (PV) of a nuclear power plant is a major safety consideration throughout the life of the power plant. Since the PV is nonreplaceable, radiation embrittlement can limit the serviceable lifetime of the PV and thereby limit the effective operating lifetime of the plant. It can further restrict normal heat-up and cool-down reactor operations, with resultant cycle-to-cycle economic implications. In recognition of these safety and economic issues, the US Nuclear Regulatory Commission (NRC) established the light water reactor LWR-PV surveillance dosimetry improvement program (SDIP) some ten years ago to improve, maintain and standardize neutron dosimetry, damage correlation, and the associated reactor analysis procedures used for predicting the integrated effect of neutron exposure to LWR-PV. The LWR-PV-SDIP adopted specific experimental and calculational strategies to meet the challenge of this complex radiation induced (PV) embrittlement phenomenon. A vigorous research effort has gone forward worldwide to implement these strategies. The major benefit of this program has been and continues to be a significant improvement in the accuracy of the assessment of the current metallurgical condition and the remaining safe operating lifetime of LWR-PV. The LWR-PV-SDIP has produced a broad range of technical accomplishments over the last decade and these achievements are reviewed. These earlier LWR-PV-SDIP accomplishments have generated, in turn, a number of significant new developments that are described. A natural outgrowth of LWR-PV-SDIP work is the experience to project future needs of LWR-PV surveillance. On this basis, recommendations for future directions are advanced with special emphasis on plant life extension. 46 refs., 2 figs., 5 tabs