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NRC Requests Additional Information for Diablo Canyon Emergency Amendment Request

Strategic Insights

— 1 min read

The United States Nuclear Regulatory Commission has issued a request for additional information regarding a proposed emergency license amendment request from Pacific Gas and Electric Company to revise the Technical Specification for the Diablo Canyon Nuclear Power Plant. The proposed changes would allow a one-time completion time of 144 hours to replace the Auxiliary Saltwater (ASW) pump 1-1 motor during Cycle 23. The NRC staff has reviewed the request and identified areas that require clarification to complete the review.

Key Takeaways:

  • The NRC staff has requested additional information from Pacific Gas and Electric Company to complete the review of the proposed emergency license amendment request.
  • The requested information includes job performance measures for tailboarding operators on providing backup cooling from firewater to charging pumps.
  • The licensee must provide clarification on the risk analysis assumptions made on common cause failure and the use of an all-hazards model to estimate core damage frequency (CDF) and large early release frequency (LERF).
  • The NRC staff is requesting information on the replacement motor and specifications of both existing and replacement motors.
  • The licensee must provide information on the expected Ultimate Heat Sink temperature for the duration of the proposed 144-hour completion time.
  • The NRC staff is seeking descriptions of contingency actions that may occur during the return of ASW Pump 1-1 to operable status.

Statistics:

  • The proposed completion time for replacing the ASW pump 1-1 motor is 144 hours.
  • The risk significance criteria for CDF/LERF is 1.0E-06 and 1.0E-07, respectively.
  • The expected Ultimate Heat Sink temperature for the duration of the proposed 144-hour completion time is not specified.

Sources:

  • Lee, Samson. United States Nuclear Regulatory Commission. From: Lee, Samson Sent: Wednesday, July 7, 2021 5:36 PM To: Richardson, Michael Subject: Request for additional information - Diablo Canyon emergency amendment request to revise Technical Specification 3.7.8, "Auxiliary Saltwater (ASW) System" (EPID L-2021-LLA-0123)
  • Regulatory Guide 1.174. United States Nuclear Regulatory Commission.

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