The following is a summary from the Diablo Canyon Part 21 Report submitted:
On May 18, 2020, Pacific Gas and Electric (PG&E) completed its evaluation of a deviation concerning commercial-grade thermocouples dedicated at Diablo Canyon Power Plant. The original defect was discovered on April 10, 2020 during bench testing where two separate thermocouples exhibited leakage during static pressure testing. The two thermocouples were tested as part of a spare safety-related pump motor refurbishment. Upon subsequent review, it was identified that a pressure boundary test had not been required as part of the dedication process, but should have for its safety-related application. These components were not installed in the plant and there was no risk to the health and safety of the public. Thermocouples from the same batch have been quarantined to prevent installation, and it has been confirmed that none of the suspect batch of thermocouples have been installed in the plant. The thermocouple replacement part evaluation has been revised to include a pressure boundary test as part of the commercial-grade dedication prior to acceptance.
Thermocouple Make and Model: March Bellofram 3060-2-JJ-2-13.00-0-1-000
The NRC Resident Inspectors have been notified.
This report only affects Diablo Canyon Power Plant.
The person informing the Nuclear Regulatory Commission:
Kenneth Cortese
Quality Verification Director
Diablo Canyon Power Plant
Pacific Gas and Electric
805-440-367
