ML18134A328

Diablo Canyon, Units 1 and 2, Change of Commitment Dates for Full Implementation of Open Phase Detection System

ML18134A328
Person / Time
Site:	Diablo Canyon
Issue date:	05/14/2018
From:	Welsch J M Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-18-036
Download: ML18134A328 (3)

Text

Pacific Gas and Electric Company* May 14, 2018 PG&E Letter DCL-18-036 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 James M. Welsch Vice President Nuclear Generation and Chief Nuclear Officer Diablo Canyon Power Plant P.O. Box 56 Avila Beach, CA 93424 805.545.3242 E-Mail: James. Welsch@pge.com Change of Commitment Dates for Full Implementation of Open Phase Detection System

References:

1. PG&E Letter DCL-14-118, "Supplement to Response to NRC Request for Additional Information Regarding Response to NRC Bulletin 2012-01 ,"dated December 22, 2014 2. PG&E Letter DCL-14-009, "Response to NRC Request for Additional Information Regarding Response to NRC Bulletin 2012-01 ,"dated February 3, 2014

Dear Commissioners and Staff:

In Reference 1, Pacific Gas and Electric Company (PG&E) committed to the following schedule for implementation of the Open Phase Detection system at Diablo Canyon Power Plant (DCPP) Units 1 and 2:

• Unit 1: Complete installation during the Unit 1 twentieth refueling outage (1 R20). Trip functions to be enabled by June 30, 2018.

• Unit 2: Complete installation during the Unit 2 twentieth refueling outage (2R20). Trip functions to be enabled by December 31, 2018. In Reference 1, PG&E additionally stated that the planned schedule for implementation of the Open Phase Detection system may be revised based on various factors. PG&E is hereby extending the schedule for enabling the trip functions for Units 1 and 2 to December 31,2019. A member of the STARS Alliance Callaway o Diablo Canyon o Palo Verde o Wolf Creek Document Control Desk May 14, 2018 Page 2 PG&E Letter DCL-18-036 PG&E selected the Open Phase Detection system that was developed by the Electric Power Research Institute and Power System Sentinel Technologies, LLC. This system was installed in each DCPP unit as previously committed. However, to improve the reliability of the equipment, digital injection source power supplies are being replaced with analog injection source power supplies. This hardware change was completed for Unit 2 in March 2018 and is planned to be completed for Unit 1 in May 2018. PG&E is extending the Open Phase Detection system monitoring period to gather more operating experience (OE) with this new hardware configuration before enabling the Open Phase Detection system trip functions at DCPP. Additional time will also provide more OE both from DCPP and from across the industry relative to the types and characteristics of grid disturbances that could cause spurious Open Phase Detection system actuations. The information obtained during the additional monitoring period will better inform the determination of the actuation setpoints and time delays for the system. This will minimize the potential for inadvertent system actuations once the trip functions have been enabled. Inadvertent system actuations during normal power operations would unnecessarily (1) reduce the availability of offsite power and (2) cause the emergency diesel generators on the affected DCPP unit to start and run unloaded. The extended monitoring period will not adversely impact the safe operation of DCPP Units 1 and 2 as summarized below:

• PG&E has taken interim corrective actions in response to this industry issue, as documented in Reference 2. As part of these interim corrective actions, PG&E will continue the daily visual inspection of the 230 kV tie-line for an open phase. As stated in Reference 2, "[t]he scope of the inspection includes the line termination at the standby/startup transformers of each unit up to switchyard disconnect switches (i.e., interface with the 230 kV busses)."

• The Open Phase Detection system alarm feature itself helps operators diagnose any potential open phase condition (OPC) in offsite power.

• During normal power operation at DCPP, an OPC affecting the immediately available 230 kV source would not impact either operating unit because the station auxiliary equipment is not connected to it. Operators would promptly respond per procedural guidance and correct the OPC in a timely manner. The Open Phase Detection trip function for the delayed access 500 kV source to DCPP is not enabled during normal power operation. A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek Document Control Desk May 14, 2018 Page 3 PG&E Letter DCL-18-036 This commitment change is processed in accordance with the Nuclear Energy Institute guidance for deviations to the OPC Initiative and NEI 99-04, "Guidelines for Managing NRC Commitment Changes." If you have any questions or require additional information regarding this schedule extension, please contact Mr. Hossein Hamzehee, DCPP Regulatory Services Manager, at 805-545-4720. Sincerely, Vice President, Nuclear Generation and Chief Nuclear Officer jmsp/4927 cc: Kriss M. Kennedy, NRC Region IV Administrator Christopher W. Newport, NRC Senior Resident Inspector Balwant K. Singal, NRC Senior Project Manager Diablo Canyon Distribution A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek