Surveillance Program Lessons Learned

The requirements for nuclear power plants to have a reactor vessel (RV) material surveillance program are codified into federal law per U.S. Nuclear Regulatory Commission (NRC) 10 CFR 50, Appendix H. The purpose of material surveillance programs is to monitor changes in the fracture toughness properties of ferritic materials in the RV under neutron irradiation and the thermal environment. Surveillance capsules are withdrawn periodically from the RV and then tested and evaluated. Results are reported following the guidelines laid forth in ASTM E185-82, Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels. Ideally, surveillance capsule lessons learned would be unnecessary; in practice, however, surveillance capsule management does not always run smoothly. Numerous lessons learned have been discovered, including lead factor lag, field failures, shipping situations, material maintenance, design decisions, and regulatory requirements. These lessons represent situations that have affected multiple nuclear plant programs and that should be mitigated in future surveillance capsule programs. Many of these lessons have been addressed with changes to the ASTM standards or shared with the industry via general operating experiences. More work is necessary between all parties, owners, vendors, and regulators to continue ensuring safe plant operation in regard to mitigating the past problems observed in the fleet-wide surveillance capsule programs from around the world.