DIABLO CANYON POWER PLANT INSIGHTS FROM APPLICATION OF USNRC INTERIM STAFF GUIDANCE

摘要

Diablo Canyon Power Plant (DCPP) is replacing the existing digital Westinghouse Eagle 21 Process Protection System (PPS) to address obsolescence and maintenance issues. The Eagle 21 system was installed in 1994 to replace the original analog Westinghouse Hagan 7100 PPS. The Nuclear Regulatory Commission (NRC) has designated the License Amendment Request (LAR) for the DCPP PPS replacement project as the pilot application for use of Digital I&C (DI&C) Interim Staff Guidance (ISG)-06, Licensing Process. ISG-06 describes the licensing process guidance the NRC staff may use to review the LAR for a DI&C modification. This paper describes PG&E participation in ISG-06 development along with the process used to prepare the LAR, which is currently under Staff review. USNRC Digital I&C (DI&C) Interim Staff Guidance (ISG) document ISG-02 describes acceptable methods for implementing diversity and defense-in-depth (D3) in digital I&C reactor protection system designs to mitigate the potential for a common-cause failure (CCF) that would disable redundant protection system channels and prevent FSARU Chapter 15 acceptance criteria from being met. The USNRC has approved the Topical Report for the PPS Replacement D3 design, which conforms to the guidance of ISG-02 Positions 1 & 2 without a Diverse Actuation System (DAS) by providing automated, independent, and diverse backup. This paper describes PG&E participation in the ISG-02 development process as well as the evolution of the PPS replacement D3 design.