DCL-21-048, Response to Request for Additional Information on Emergency License Amendment Request 21-05, Revision to Technical Specification 3.7.8, 'Auxiliary Saltwater (Asw) System'

Response to Request for Additional Information on Emergency License Amendment Request 21-05, Revision to Technical Specification 3.7.8, 'Auxiliary Saltwater (Asw) System'

ML21189A001
Person / Time
Site:	Diablo Canyon
Issue date:	07/07/2021
From:	Gerfen P Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-21-048
Download: ML21189A001 (7)

Text

mPacific Gas and Beclric Campany*

Paula Gerfen Site Vice President Diablo Canyon Power Plant Mail code 104/6/605 P.O. Box 56 Avila Beach, CA 93424 805.545.4596 Internal: 691.4596 Fax: 805.545.4234 PG&E Letter DCL-21-048 10 CFR 50.91 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Response to Request for Additional Information on Emergency License Amendment Request 21-05, Revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System

Reference:

1. PG&E Letter DCL-21-046, Emergency License Amendment Request 21-05, Revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System, dated July 7, 2021 [ADAMS Accession No. ML21188A214].

2. NRC email dated July 7, 2021

Dear Commissioners and Staff:

In Reference 1, Pacific Gas and Electric Company (PG&E) submitted an Emergency License Amendment Request for revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System. In Reference 2, the NRC Staff provided a request for additional information (RAI) via an e-mail, dated July 7, 2021. The Enclosure to this letter provides PG&E responses to the RAI.

This letter does not include any new or revised regulatory commitment (as defined by NEI 99-04).

If you have any questions or require additional information, please contact Mr. James Morris, Regulatory Services Manager, at (805) 545-4609.

I state under penalty of perjury that the foregoing is true and correct.

7/7/2021 Executed on Date: ____________

Sincerely, Paula Gerfen A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Document Control Desk PG&E Letter DCL-21-048 Page 2 kjse/51124688 Enclosure cc: Diablo Distribution cc/enc: Donald R. Krause, NRC Senior Resident Inspector Samson S. Lee, NRR Senior Project Manager Scott A. Morris, NRC Region IV Administrator Gonzalo L. Perez, Branch Chief, California Department of Public Health A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

PG&E Letter DCL-21-048 Enclosure Response to Request for Additional Information on Emergency License Amendment Request 21-05, Revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System

Background:

By letter dated July 7, 2021, Pacific Gas and Electric Company (PG&E or the licensee) submitted an emergency license amendment request (LAR) to revise the Technical Specification (TS) for the Diablo Canyon Nuclear Power Plant, Unit 1 (Diablo Canyon or DCPP) (ADAMS Accession No. ML21188A214). The proposed amendments would provide a new TS 3.7.8 Condition A note to allow a one-time Completion Time (CT) of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> to replace the Auxiliary Saltwater (ASW) Pump 1-1 motor during Cycle 23. The NRC staff has reviewed the LAR and determined that additional information is required to complete the review. The NRC staffs requests for additional information (RAIs) are listed below. The PG&E staff indicated that a clarification call is not necessary. The PG&E staff requested, and NRC agreed, to an RAI response by July 7, 2021.

NRC Question RAI APLA-1:

Risk Insights:

RAI APLA-1 For DCPP ASW Pump 1-1:

1.In the LAR, the licensee indicated that they will tailboard [pre-job brief] operators on providing backup cooling from firewater to charging pumps.

a. Are there any job performance measures for this activity?

b. Describe the nature of the reactor coolant pump (RCP) seals and any enhancement (i.e., Gen III SHIELD shutdown seal or Abeyance).

2.Will there be any restrictions on performing on-line maintenance for other systems, structures, and components (SSCs) during the extended allowable outage time (AOT)?

3.When doing the risk analysis, what assumptions were made on common cause failure (CCF) and why?

4.Was an all-hazards model used to estimate core damage frequency (CDF)/large early release frequency (LERF)?

1

PG&E Letter DCL-21-048 Enclosure PG&E Response: RAI APLA-1 1.a:

Yes. There are three job performance measures (JPM) that simulate the manual alignment of firewater to charging pumps on both Units. Two JPMs are alternate path and the other incorporates no malfunctions during procedure performance. The alternate path JPM incorporates malfunctions of components that requires the operator to perform actions other than those performed when a system responds normally. This task is required to be performed during initial qualification for operators and the JPMs are part of the exam bank of JPMs that can be randomly selected for Operator Annual Exams.

PG&E Response: RAI APLA-1 1.b:

DCPP has installed Westinghouse GEN III SHIELD shutdown seals in all four RCPs in both units.

PG&E Response: RAI APLA-1 2:

Maintenance and testing on protected equipment listed in the LAR will be restricted.

A sensitivity case was performed in support of providing Probabilistic Risk Assessment (PRA) risk insights. The sensitivity case evaluated numerical impacts (additional incremental conditional core damage probability and the incremental conditional large early release probability) of performing pre-planned on-line maintenance of other SSCs while the ASW Pump 1-1 is in TS 3.7.8 Condition A for the proposed CT of 144-hours. The results of the sensitivity case show that a significant margin remains when compared to Regulatory Guide (RG) 1.174 and DCPP on-line maintenance risk significance criteria.

PG&E Response: RAI APLA-1 3:

The common cause and independent failure probabilities for the ASW pumps were left unchanged in the LAR PRA model. This modeling decision was made because there is currently not sufficient information regarding the cause of the ASW Pump 1-1 motor ground or extent of condition for the other ASW motors to make a different decision. Use of the baseline CCF assumptions account for contributions to risk from both independent and CCFs and represents a reasonable approach when cause data is not available.

PG&E Response: RAI APLA-1 4:

The PRA analysis was based on an all-hazards model, which includes Internal Events, Internal Flooding, Internal Fire Events, and Seismic Events.

2

PG&E Letter DCL-21-048 Enclosure RAI APLA-2 In the LAR, Section 3 under Risk Insights, it was stated that, The results demonstrate that ICCDP [incremental conditional core damage probability] and ICLERF [incremental conditional large early release frequency] are below the risk significance criteria of Regulatory Guide (RG) 1.174, 1.0E-06 and 1.0E-07, respectively. Therefore, the proposed separate one-time extension of TS 3.7.8 Condition A Required Action to 6-days for emergent maintenance for ASW Pump 1-1 Motor is considered to not be risk significant. It was not clear to the staff which measure of risk was used since RG 1.174 refers to CDF/LERF and CDF/LERF.

a. Clarify if ICLERP was intended in lieu of ICLERF and if so, should RG 1.177 guidance on ICCDP/ICLERP be cited for this one-time TS change?

b. If not, justify how RG 1.174 metrics were used to conclude that maintenance on ASW Pump 1-1 Motor is not risk significant.

PG&E Response: RAI APLA-2.a:

Yes, ICLERP was intended in lieu of ICLERF. PG&E agrees that RG 1.177 should be referenced instead of RG 1.174 for a one-time TS CT change. The use of ICCDP and ICLERP defined in RG 1.177 was intended. The risk significance criteria of 1.0E-06 and 1.0E-07 for ICCDP and ICLERP from RG 1.177 was correctly used to demonstrate low risk significance of the proposed change.

PG&E Response: RAI APLA-2.b:

The risk significance criteria of 1.0E-06 and 1.0E-07 for ICCDP and ICLERP from RG 1.177 was used to demonstrate low risk significance of the proposed change and therefore justification of use of RG 1.174 metrics is not required. Under RG 1.177 risk significance criteria for ICCDP and ICLERP, an additional extension of TS 3.7.8 Condition A CT of 72-hours is not considered risk significant.

NRC Question RAI EEEB-1 Electrical Engineering:

RAI EEEB-1 In the LAR, the licensee stated that the proposed changes would revise the operating license to provide a new TS 3.7.8 Condition A note to allow a one-time CT of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> to replace the ASW Pump 1-1 motor during Cycle 23. Please clarify the type of the replacement motor and the specifications of both existing and replacement motors. Also, please confirm no load changes as the result of the motor replacement.

3

PG&E Letter DCL-21-048 Enclosure PG&E Response:

The data for the replacement pump and existing pump are the same for the replacement motor and existing motor including a horsepower (HP) of 465 HP.

There are no load changes that result from the motor replacement.

Replacement and Existing ASW Pump 1-1 motor data:

EFFICIENCY 94%

HORSEPOWER 465 HP VOLTAGE 4000 VOLTS AMPS 61.7 AMPS SPEED 887 RPM NRC Question RAI SNSB-1 Reactor Systems:

RAI SNSB-1 The LAR states, The TS 3.7.9 Ultimate Heat Sink (UHS) requirements are currently being met with the UHS (Pacific Ocean) temperature below 64°F. Given that the safety analysis assumes a maximum ASW temperature of 64°F, provide information on the expected UHS temperature for the duration of the proposed 144-hour CT in order to assure that the single operable train of ASW will continue to meet the design basis.

PG&E Response:

A southerly flowing current will continue through Sunday July 11, 2021, and intake seawater temperatures will remain below 64°F for the duration of the proposed one-time 144-hour CT.

NRC Question RAI EMIB-1 Mechanical Engineering:

RAI EMIB-1 In Section 2.0, Detailed Description, under Reason for the Proposed Change, it is stated, It is expected an additional 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> beyond the 72-hour completion time could be required to address contingency actions that may occur during the return of ASW Pump 1-1 to OPERABLE status. Provide a description of the contingency actions.

4

PG&E Letter DCL-21-048 Enclosure PG&E Response:

The following are issues that DCPP has experienced while performing component replacements of this nature and specifically to the vertically mounted ASW Motor/Pump configuration. Any one or combination of these issues could result in additional time in the duration required to replace the motor and complete the operability verification testing:

• Proper function of the motor space heater, requiring diagnose and repair

• Problems with removal of the coupling half from the existing motor or reinstallation on the new motor

• Achieving proper alignment of the pump to motor coupling

• Achieving proper tolerances on the motor seismic restraint

• Not achieving acceptance criteria of the specified operability verification testing and needing to perform the contingency operability verification testing

• Problems racking in the 4 kilovolt (kV) motor breaker

• Elevated vibration during test run warranting installation of balance weight

• Problems with reinstallation of the termination box on the new motor and re-termination of the 4 kV leads

• Potential reverse rotation following re-termination due to the nature of 3-phase motors 5