DCL-23-120, License Amendment Request 23-03 Revision to Technical Specification 3.7.8, Auxiliary Saltwater (Asw) System

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License Amendment Request 23-03 Revision to Technical Specification 3.7.8, Auxiliary Saltwater (Asw) System
ML23319A204
Person / Time
Site: Diablo Canyon 
Issue date: 11/14/2023
From: Petersen B
Pacific Gas & Electric Co
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
DCL-23-120
Download: ML23319A204 (25)
v • d • e


Text

Dennis B. Petersen Station Director Diablo Canyon Power Plant Mail code 104/5/502 P.O. Box 56 Avila Beach, CA 93424 805.545.4022 Dennis.Petersen@pge.com A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

  • Diablo Canyon
  • Palo Verde

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.91, Pacific Gas and Electric Company (PG&E) hereby requests approval of the enclosed proposed amendment to Facility Operating License No. DPR-80 for Unit 2 of the Diablo Canyon Power Plant (DCPP). The enclosed license amendment request (LAR) proposes to revise the DCPP Technical Specification (TS) 3.7.8, Auxiliary Saltwater (ASW) System.

The enclosure to this letter contains the evaluation of the proposed change.

PG&E requests approval of this LAR on an exigent basis no later than at 19:00 PST on December 8, 2023. PG&E requests the license amendment be made effective upon NRC issuance, to be implemented within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> from the date of issuance.

PG&E makes no regulatory commitment (as defined by NEI 99-04) in this letter.

This letter includes no revisions to existing regulatory commitments.

In accordance with site administrative procedures and the Quality Assurance Program, the proposed amendment has been reviewed by the Plant Staff Review Committee.

Pursuant to 10 CFR 50.91, PG&E is sending a copy of this proposed amendment to the California Department of Public Health.

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

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

m PacHic Gas and Electric Company*

Document Control Desk Page 2 Sincerely, Dennis B. Petersen Station Director Executed on:

kjse/ SAPN 51201169 Enclosures Date cc:

Diablo Distribution PG&E Letter DCL-23-120 cc/enc: Anthony Chu, Branch Chief, California Dept of Public Health Mahdi 0. Hayes, NRG Senior Resident Inspector Samson S. Lee, NRR Project Manager John D. Monninger, NRG Region IV Deputy Administrator A

member of the STARS (Strategic Teaming and Resource Shari ng)

Al liance Callaway

  • Diablo Canyon
  • Palo Verde
  • Wolf Creek

Enclosure PG&E Letter DCL-23-120 Evaluation of the Proposed Change

Subject:

License Amendment Request 23-03, Revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System

1.

SUMMARY

DESCRIPTION

2.

DETAILED DESCRIPTION 2.1 Description of the Proposed Change 2.2 System Design and Operation 2.3 Current Technical Specifications Requirements 2.4 Reason for the Proposed Change

3.

TECHNICAL EVALUATION

4.

REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration Analysis 4.4 Conclusions

5.

ENVIRONMENTAL CONSIDERATION

6.

REFERENCES ATTACHMENTS:

1.

Proposed Technical Specification Change

2.

Revised Technical Specification Page

3.

Technical Specification Bases Changes

Enclosure PG&E Letter DCL-23-120 1

EVALUATION

1.

SUMMARY

DESCRIPTION The proposed change(s) will revise the Diablo Canyon Unit 2 Operating License to provide a revised TS 3.7.8, Auxiliary Saltwater (ASW) System, Condition A note to allow a one-time Completion Time 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 2-2 motor during Cycle 24.

The TS 3.7.8 change requested in this exigent LAR provides a more appropriate TS 3.7.8 Completion Time that is commensurate with the online risk associated with one of two ASW pumps inoperable. The online risk for the proposed ASW system Completion Time based on risk insights is considered to not be risk significant due to the redundancy in the design of the ASW system. The TS 3.7.8 change will avoid an unnecessary plant shutdown during the expected time needed to perform the replacement of the ASW Pump 2-2 motor, and associated post-maintenance inspections and testing.

The change requested in this LAR will prevent an unnecessary Unit 2 shutdown for a low-risk scenario, and is consistent with safely maintaining DCPP generation and thereby supporting electrical grid reliability in California.

The need to replace the ASW Pump 2-2 motor occurred on an emergent basis due to indication of a potential degraded motor bearing. The ASW Pump 2-2 motor is currently OPERABLE but trends in bearing performance indicate that OPERABILITY could be impacted prior to the next scheduled Unit 2 refueling outage in April 2023. In order to maintain high plant safety, PG&E currently plans to begin replacement of the ASW Pump 2-2 motor the week of December 11, 2023 with a spare ASW pump motor.

Accordingly, PG&E requests approval of this LAR on an exigent basis no later than at 19:00 PST on December 8, 2023.

2.

DETAILED DESCRIPTION 2.1 Description of Proposed Change The TS 3.7.8 Condition A Completion Time is revised to provide a revised note for the current "72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />" Completion Time:

A Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> is Applicable for ASW pump 2-2 on a one-time basis, for Unit 2 cycle 24.

Enclosure PG&E Letter DCL-23-120 2

The proposed TS change is noted on the marked-up TS page provided in Attachment 1.

The proposed retyped TS is provided in Attachment 2.

The TS Bases changes for TS 3.7.8 Condition A are included in Attachment 3 for information only and will be implemented in accordance with the TS Bases Control Program.

In summary, the TS 3.7.8 Condition A Completion Time is revised to allow a one-time Completion Time of 144-hours for ASW Pump 2-2 during Unit 2 Cycle 24 to support replacement of the ASW Pump 2-2 motor. The one-time Completion Time of 144-hours for ASW Pump 2-2 supports emergent replacement of the ASW Pump 2-2 motor. The proposed one-time 144-hour Completion Time reasonably avoids a potential unnecessary shutdown of DCPP Unit 2 due to the current 72-hour Completion Time of TS 3.7.8 Condition A being exceeded.

2.2 System Design and Operation The ASW system provides a heat sink from the Pacific Ocean for the removal of process and operating heat from the component cooling water (CCW) system. The CCW system then provides cooling to PG&E Design Class I components during all modes of operation, including a design basis accident (DBA), and also to various non-PG&E Design Class I components during normal operation and shutdown.

The ASW system consists of two, 100 percent capacity, PG&E Design Class I, cooling water trains. Each train consists of one 100 percent capacity pump, one CCW heat exchanger, piping, valving, and instrumentation. The pumps are automatically started upon receipt of a safety injection signal or 4 kilovolt (kV) automatic transfer. The normal configuration is for one train operation with the second pump cross-tied in stand-by and the second heat exchanger valved out-of-service except when the ultimate heat sink temperature is 64 degrees Fahrenheit (°F) or higher; therefore no valve realignment occurs with a safety injection signal.

Cross-tie capability of the ASW system exists between the DCPP units. Manual and remote manual system realignment provides for utilization of the second CCW heat exchanger, for use of the standby pump on the same unit, for cross-tying the standby ASW pump from the opposite unit, and for train separation for long-term cooling. The ASW unit cross-tie valve allows one ASW pump on one unit to supply the CCW heat exchanger(s) on the other unit. In the event of a total loss of ASW in one unit, the capability to cross-tie units ensures the availability of sufficient redundant cooling capacity for the affected unit. If the unit cross-tie capability were used, the unit with no operable ASW train would enter Limiting Condition for Operation (LCO) 3.0.3, and the unit from which ASW was being provided would be in a TS 3.7.8 Action A 72-hour Required Action with the cross-tie then declared inoperable.

Enclosure PG&E Letter DCL-23-120 3

The principal PG&E Design Class I function of the ASW system is the removal of decay heat from the reactor via the PG&E Design Class I CCW System. The ASW system satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii). Additional information about the design and operation of the ASW system is presented in the Updated Final Safety Analysis Report (UFSAR), Section 9.2.7.

The design basis of the ASW system is for one ASW train, in conjunction with the CCW System and the containment cooling systems, to remove accident generated and core decay heat following a design basis loss-of-coolant accident (LOCA) as discussed in the UFSAR, Section 6.2. The ASW system can be re-configured to maintain the CCW temperature to within its design bases limits. The ASW system is designed to perform its function with a single failure of any active component, with or without the loss of offsite power. This assumes a maximum ASW supply temperature of 64°F occurring simultaneously with maximum heat loads on the system. The ASW system, in conjunction with the CCW System, also cools the unit from residual heat removal (RHR) entry conditions to MODE 5 during normal and post-accident operations. The time required for this evolution is a function of the number of ASW pumps, CCW heat exchangers, and RHR heat exchangers that are operating. One ASW train is sufficient to remove decay heat during subsequent operations in MODES 5 and 6. However, in the split-train configuration during post-accident operation, operator action may be required to realign the ASW and CCW systems to prevent loss of all cooling to containment and PG&E Design Class 1 systems following specific active failure scenarios.

2.3 Current Technical Specifications Requirements Two ASW trains are required to be OPERABLE by TS 3.7.8 to provide the required redundancy to ensure that the system functions to remove post-accident heat loads, assuming that the worst-case single active failure occurs coincident with the loss of offsite power.

An ASW train is considered OPERABLE during MODES 1, 2, 3, and 4 when:

a. The pump is OPERABLE,
b. The associated piping, valves, heat exchanger, and instrumentation and controls required to perform the PG&E Design Class I function are OPERABLE, and
c. The associated pump vault drain check valve is OPERABLE.

An LCO 3.7.8 OPERABLE ASW train requires that at least one vacuum relief valve be OPERABLE. Each ASW train has a vacuum relief system consisting of two vacuum relief valves (check valves) which function to prevent water hammer in the system piping during an ASW pump trip and restart transient. The second vacuum relief valve on each header ensures reliability of the function.

Both train cross-tie valves are required to be open to support single active failure criteria. The valves may be closed in post-accident long-term phase to support passive failure criteria, if system integrity is a concern. With one or both ASW trains in service

Enclosure PG&E Letter DCL-23-120 4

with the cross-tie valves closed, a single active failure could result in a significant reduction or loss of heat removal capability. With both ASW trains in service, approximately one-half of the total CCW flow is routed through each CCW heat exchanger. In the event of a postulated ASW pump failure in this configuration, with the cross-tie valves closed, only one ASW pump would be operating and providing heat removal to one-half of the total CCW flow via its associated in-service CCW heat exchanger. In this situation, the ASW systems heat removal capability is limited and may not meet the requirements of the system to maintain the CCW supply temperature within its design limits.

An LCO 3.7.8 OPERABLE ASW train also requires the ASW pump vault check valves prevent flooding of the ASW pump vaults during design flood events.

The TS 3.7.8 applicability for the ASW system is MODES 1, 2, 3, and 4. The ASW system is a normally operating system that is required to support the OPERABILITY of the equipment serviced by the ASW system and required to be OPERABLE in these MODES. In MODES 5 and 6, the OPERABILITY requirements of the ASW system are determined by the systems it supports.

TS 3.7.8 Condition A is for one ASW train inoperable. If one ASW train is inoperable, action must be taken to restore OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In this Condition, the remaining OPERABLE ASW train is adequate to perform the heat removal function.

However, the overall reliability is reduced because a single failure in the OPERABLE ASW train could result in loss of ASW system function. The Condition A 72-hour Completion Time is based on the redundant capabilities afforded by the OPERABLE train, and the low probability of a DBA occurring during this time period. If the TS 3.7.8 Condition A Completion Time is not met, TS 3.7.8 Condition B must be entered and requires plant shutdown to MODE 3 entry in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 4 entry in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

The current TS 3.7.8 Condition A Required Action A.1 Completion Time contains a note approved in Unit 1 Amendment 238 (Reference 2) that provided a one-time basis Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> that was applicable for ASW Pump 1-1 for Unit 1 cycle

23.

2.4 Reason for the Proposed Change The currently installed ASW Pump 2-2 motor was installed during Unit 2 refueling outage 23 (2R23) in November 2022. On December 27, 2022, maintenance personnel performed an oil sample on the ASW Pump 2-2 motor. The lower motor bearing oil sample was discolored indicating existence of material contamination. Subsequent to collection of the oil sample, maintenance personnel flushed oil through the lower bearing reservoir, and completed maintenance verification testing satisfactory.

As a result of the discovery of the discolored oil sample on December 27, 2022, actions were taken to implement bi-weekly oil sample collection and recording of pump vibration

Enclosure PG&E Letter DCL-23-120 5

readings for ASW Pump 2-2 to monitor motor health. The bi-weekly oil samples and recording of pump vibration readings continued from January 2023 through May 2023.

In May 2023, engineering determined that sample quality was continuing to improve, there was no change in vibration readings, and that there were no indications of bearing damage or wear (e.g., increasing or constantly elevated iron content). The initial discolored oil sample from December 27, 2022, was attributed to pump run in of the bearing after installation of the ASW Pump 2-2 pump and motor in 2R23, and not to motor bearing damage.

On August 21, 2023, an ASW Pump 2-2 oil sample collected by maintenance personnel exhibited darker than normal oil. A ferrography test performed by engineering on the oil identified existence of iron particles. Vibration surveys were conducted on ASW Pump 2-2 and no abnormalities were observed. The results were consistent with past vibration surveys. System health of the ASW Pump 2-2 was monitored through establishment of enhanced vibration surveys which showed no abnormalities with regard to motor bearing degradation and no changes from past vibration surveys.

On October 23, 2023, the ASW Pump 2-2 oil sample visually exhibited further discoloration compared to the sample collected on August 21, 2023 indicating that degradation had continued. As a result, the oil sample was sent to an offsite vendor for analysis. The vendor report identified elevated iron concentrations and therefore PG&E implemented the vendor report recommendation to check pump vibration data and reduce oil contaminant levels.

On November 5, 2023, ASW Pump 2-2 oil flushes were performed on the lower oil reservoir and the collected oil sample exhibited improved oil condition. The pump vibration data is within normal operating limits.

As a result of the indication of a potential degraded ASW Pump 2-2 motor bearing on October 23, 2023, and as a prudent measure to maintain high reliability of the ASW pump, PG&E currently plans to begin replacement of the ASW Pump 2-2 motor on the week of December 11, 2023, with a spare ASW pump motor. The spare ASW pump motor to be installed has been used in Unit 2 previously and is electrically equivalent to the current ASW Pump 2-2 motor. Preservice activities being performed on the spare ASW pump motor to prepare it for installation are hand cleaning of motor, advanced winding analysis, oil flush, motor space heater testing, and end play adjustment (as needed).

The following required actions will be performed to support replacement of the ASW Pump 2-2 motor with estimated work planning durations in parentheses:

  • Install ground buggy (6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />)
  • Install personal grounds (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />)
  • De-terminate and remove existing motor (18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />)

Enclosure PG&E Letter DCL-23-120 6

  • Install replacement motor, perform uncoupled pump test (48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />)
  • Remove personal grounds (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />)
  • Remove ground buggy for lift (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />)
  • Install ground buggy after lift (6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />)
  • Perform coupled test run (8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />)
  • Touch-up coatings (10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />)
  • Perform post-maintenance operational verification testing required to declare ASW Pump 2-2 OPERABLE (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />)
  • Operations review of operational verification testing results for operability As demonstrated above, it is estimated that more than the full TS 3.7.8 Condition A Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> will be required, without any contingency time, to return the ASW Pump 2-2 to OPERABLE status.

Based on operating experience, the following are potential issues that could arise while performing component replacements of this nature in the vertically mounted ASW Motor/Pump configuration. Any or a combination of these issues could result in additional contingency actions and time in the duration required to replace the motor and complete the ASW Pump 2-2 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 It is expected that up to 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 2-2 to OPERABLE status. The DCPP Units 1 and Unit 2 ASW pumps are OPERABLE. The TS 3.7.9 Ultimate Heat Sink (UHS) requirements are currently being met with the UHS (Pacific Ocean) temperature below 64°F. The ocean temperature in December rarely, if ever, approaches 64°F.

The results of recent surveillance testing for ASW Pump 1-1, ASW Pump 1-2, and ASW Pump 2-1 confirming OPERABILITY are:

Enclosure PG&E Letter DCL-23-120 7

ASW Pump 1-1:

The last routine pump surveillance test November 3, 2023 - results were within acceptance criteria Last oil sample collected on July 17, 2023 - results were within acceptance criteria ASW Pump 1-2:

This pump was replaced during Unit 1 Refueling outage 24. The last routine surveillance test was on November 2, 2023 as part of a preservice test - results were within acceptance criteria Last oil sample collected on November 5, 2023 - initial results were acceptable ASW Pump 2-1:

The last routine ASW Pump 2-1 quarterly test was performed on November 7, 2023.

Test results were within acceptance criteria.

Vibration data is collected on a quarterly basis. The most recent data from November 14, 2023, indicates stable trends at the motor, and no indications of mechanical degradation are detected.

Upper and lower bearing oil samples were collected on June 20, 2023, for routine monitoring - upper bearing overall results are satisfactory. Lower bearings results indicated slightly higher particle count. This condition has been present since motor installation in 2018 and is trending down. The Analytical Ferrography section of the most recent oil analysis reports a normal wear situation.

Bearing temperature trends have been reviewed and are normal and stable. Based on routine vibration monitoring, oil analysis, and bearing temperature trends, there is no evidence of early stage bearing degradation on ASW Pump 2-1 and the pump is determined acceptable for service.

The circumstances requiring this exigent amendment request could not reasonably have been avoided. Oil samples collected from ASW pump 2-2 in January 2023 up until August 21, 2023, were within acceptance limits.

When ASW pump 2-2 is declared inoperable to perform the motor replacement, PG&E will perform work on the ASW Pump 2-2 on a 24-hour per day basis until the pump is returned to OPERABLE status.

A one-time change for the ASW pump 2-2 Completion Time is being requested because PG&E has submitted an LAR (Reference 5) requesting NRC approval of Technical Specifications Task Force (TSTF) TSTF-505 which will allow upon approval PG&E calculation of a risk-informed Completion Time for TS 3.7.8 Action A of up to 30 days.

Enclosure PG&E Letter DCL-23-120 8

Prompt action is requested for the NRC to approve an exigent amendment to TS 3.7.8 Condition A to provide an additional one-time period of 72-hours beyond the current 72-hour Completion Time (144 total hours) during Unit 2 Cycle 24 to allow replacement of the ASW Pump 2-2 motor currently planned on December 11, 2023.

3.

TECHNICAL EVALUATION Technical Specification Changes The TS 3.7.8 Condition A Completion Time is revised to allow a one-time -time Completion Time of 144-hours during Unit 2 Cycle 24. The one-time Completion Time of 144-hours for the ASW Pump 2-2 supports emergent replacement of the ASW Pump 2-2 motor.

TS 3.7.8 Condition A corresponds to a level of degradation in which one train of the ASW system is inoperable and the system has lost its redundancy to perform the heat removal function. The ASW system is designed to perform its function with a single failure of any active component, with or without the loss of offsite power. This assumes a maximum ASW temperature of 64°F occurring simultaneously with maximum heat loads on the system. In addition, cross tie capability of the ASW system exists between the DCPP units. Manual and remote manual system realignment provides for utilization of the second CCW heat exchanger, for use of the standby pump on the same unit, for cross-tying the standby ASW pump from the opposite unit, and for train separation for long term cooling. The ASW unit cross-tie valve allows one ASW pump on one unit to supply the CCW heat exchanger(s) on the other unit. In the event of a total loss of ASW in Unit 2, the capability to cross-tie units ensures the availability of sufficient redundant cooling capacity for Unit 2. It is noted that if the Unit 2 ASW Pump 2-1 were also to become inoperable and unit cross-tie capability were used, Unit 2 would have no operable ASW train and would enter LCO 3.0.3, and Unit 1 would be in a TS 3.7.8 Condition A 72-hour action with the cross-tie declared inoperable.

The one-time Completion Time of 144-hours for the ASW Pump 2-2 during Cycle 24 is reasonable based on the capabilities of the other ASW Pump 2-1 to perform the heat removal function, the cross-tie capabilities of ASW from Unit 1, the low probability of a design basis accident occurring during this period, the one-time use of a 144-hour Completion Time, and that it provides sufficient time to perform the emergent replacement of the ASW Pump 2-2 motor and the required post-maintenance testing. In addition, based on risk insights using the DCPP Probabilistic Risk Assessment (PRA) model, the 144-hour Completion Time for ASW Pump 2-2 has been determined to not be risk significant. Risk management actions have been determined (see Risk Insights section below) based on evaluation of the insights from the PRA assessment and have been accepted by Operations to be implemented during the proposed TS 3.7.8 Action A 144-hour Completion Time:

Enclosure PG&E Letter DCL-23-120 9

The proposed one-time 144-hour Completion Time reasonably avoids a potential unnecessary Unit 2 shutdown due to the current 72-hour Completion Time of TS 3.7.8 Condition A being exceeded during the emergent replacement of the ASW Pump 2-2 motor.

Technical Specification Bases Changes The TS Bases for the TS 3.7.8 Condition A Completion Time are updated as follows:

The 72-hour Completion Time is modified by a Note that allows a one-time Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> for ASW pump 2-2, for Unit 2 cycle 24 to support emergent replacement of the ASW pump 2-2 motor. The one-time Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> is reasonable considering the capabilities of the other ASW Pump 2-1 to perform the heat removal function, the cross-tie capabilities of ASW from Unit 1, the low probability of a design basis accident occurring during this period, and the one-time use of a 144-hour Completion Time.

The TS Bases change reflects the change to TS 3.7.8 for the one-time 144-hour Completion Time for ASW Pump 2-2. The TS Bases change will be implemented in accordance with the TS Bases Control Program as part of amendment implementation.

Risk Insights This LAR is not a risk-informed LAR. However, for additional information, the risk insights determined with the DCPP PRA model are summarized here.

Extending the Completion Time of one train of the ASW system out for maintenance has been assessed using the DCPP PRA model, which is an all-hazard model including Internal Events, Internal Flooding, Internal Fire Events, and Seismic Events. All of the DCPP PRA models have been peer reviewed and assessed using PRA Standard ASME/ANS RA-Sa-2009 and RG 1.200 Revision 2. All peer review F&Os have been closed using the process documented in Appendix X to NEI 05-04/07-12/12-16, Close-out of Facts and Observations (F&Os)..

For the PRA assessment, the total additional exposure time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is used.

This is based on the proposed extension of the current Completion Time from 72-hours (3-days) to 144-hours (6-days). The incremental conditional core damage probability (ICCDP) and the incremental conditional large early release probability (ICLERP) using the Core Damage Frequency and Large Early Release Frequency increase above the baseline plant risk have been calculated to be 1.0E-06 and 1.0E-07, respectively. The results demonstrate that ICCDP

Enclosure PG&E Letter DCL-23-120 10 and ICLERP are below the risk significance criteria of Regulatory Guide 1.177.

Therefore, the proposed separate one-time extension of TS 3.7.8 Condition A Required Action A.1 to 6-days for emergent maintenance for ASW Pump 2-2 motor is considered to not be risk significant.

The PRA evaluation conservatively includes an impact to common cause even though there is currently not sufficient information to guide and support a meaningful extent of condition for the other ASW motors. The ASW Pump 2-2 was set to guaranteed failure in the PRA evaluation. The failure-to-run and fail-to-start probabilities of the other three ASW pumps were set to the Alpha 2 parameter of common cause group of 4 from Section 2.1.8.1 of INL/EXT 62940, CCF Parameter Estimations, 2020 Update, November 2021.

During the ASW Pump 2-2 replacement, in accordance with plant procedures planned maintenance of high risk SSCs will be minimized to the extent possible, and low and medium risk maintenance be managed in accordance with the maintenance rule.

The following risk management actions have been determined to be appropriate based on evaluation of the insights from the PRA assessment and will be implemented during the proposed TS 3.7.8 Condition A Required Action 144-hour (6-day) Completion Time:

  • Protect ASW Pumps 1-1, 1-2, and 2-1 and the ASW unit crosstie
  • Protect both Unit 2 CCW heat exchangers
  • Protect Charging Pump 2-3
  • Protect AFW pump trains 2-1, 2-2 and 2-3
  • Brief operators on the action to provide backup firewater cooling to the Unit 2 Centrifugal Charging Pumps
  • Protect the Diesel Emergency Generators on Unit 2 In accordance with plant procedures, the maintenance and testing of the above protected equipment will be restricted.

For the above risk management action to brief operators on the action to trip the RCPs on a loss of CCW, DCPP has installed Westinghouse GEN III SHIELD shutdown seals in all four RCPs in both units.

For the above risk management action to brief operators on the action to provide backup firewater cooling to the charging pumps, operators are trained through job performance measures that simulate the manual alignment of firewater to charging pumps on both units.

Enclosure PG&E Letter DCL-23-120 11 The proposed change has been determined to not be risk significant, and it does not:

  • Substantially increase the likelihood or consequences of accidents that are risk significant but are beyond the design and licensing basis of the plant,
  • Degrade multiple levels of defense, or cornerstones in the reactor oversight process, through plant operations or situations not explicitly considered in the development of the regulations,
  • Significantly reduce the availability or reliability of structures, systems, or components that are risk significant but are not required by regulations, or
  • Involve changes for which the synergistic or cumulative effects could significantly impact risk, Therefore, the proposed change does not create a special circumstance described in Appendix D, Use of Risk Information in Review of Non-Risk-Informed License Amendment Requests, of NUREG-0800 (Standard Review Plan), Chapter 19.2, Review of Risk Information Used to Support Permanent Plant-Specific Changes to the Licensing Basis: General Guidance.

ASW TS 3.7.8 Action A Completion Time Change Summary/Conclusion The impact on the ASW system has been evaluated for the proposed revised TS 3.7.8 Condition A that provides a one-time Completion Time of 144-hours for ASW Pump 2-2 during Unit 2 Cycle 24.

The plant configuration, while in the proposed TS 3.7.8 Condition A Completion Time of 144-hours, is bounded by the UFSAR accident analyses since the ASW system heat removal function can still be performed by the OPERABLE ASW Pump 2-1.

In addition, based on risk insights using the DCPP PRA model, the one-time 144-hour Completion Time proposed for TS 3.7.8 Condition A for Unit 2 Cycle 24 has been determined to not be risk significant. Risk management actions have been determined, based on insights from the PRA evaluation, and have been accepted by Operations to be implemented during the proposed TS 3.7.8 Condition A 144-hour Completion Time.

Only a one-time TS change for the ASW pump 2-2 Completion Time is being requested because PG&E has submitted an LAR (Reference 5) which will allow, upon approval, PG&E calculation of a risk-informed Completion Time for TS 3.7.8 Action A of up to 30 days.

Enclosure PG&E Letter DCL-23-120 12

4.

REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria The proposed change to the requirements in TS 3.7.8, Auxiliary Saltwater (ASW) System Condition A is to allow a one-time Completion Time of 144-hours for ASW Pump 2-2 during Unit 2 Cycle 24. The one-time Completion Time of 144-hours for ASW Pump 2-2 supports emergent replacement of the pump motor.

General Design Criteria DCPP Units 1 and 2 were designed to comply with the Atomic Energy Commission (AEC) (now the Nuclear Regulatory Commission, or NRC) General Design Criteria (GDC) for Nuclear Power Plant Construction Permits, published in July 1967. PG&E has made subsequent commitments to GDCs issued later that are discussed in Section 3.1 of the DCPP UFSAR. Since the requested change does not involve any change to the ASW system design function and it only allows a separate one-time extension to an existing TS Completion Time, controlled by 10 CFR 50.36, for one train of the ASW system being inoperable, there is no impact on the compliance to the GDC applicable to the ASW system.

10 CFR 50.36 - TS Regulation in 10 CFR 50.36(c)(2)(i) states, in part, that:

Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition for operation of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.

The TS remedial actions must provide the requisite reasonable assurance of public health and safety. With the proposed change to the TS 3.7.8 Condition A Completion Time, the ASW system will continue to be able to perform the heat removal function for a DBA. The proposed 144-hour Completion Time can only be used once for ASW Pump 2-2 during Unit 2 Cycle 24. Therefore, the requisite reasonable assurance of public health and safety will continue to be provided.

There are no changes being proposed such that compliance with any of the regulatory requirements above would come into question. The evaluations documented above confirm that PG&E will continue to comply with all applicable regulatory requirements.

In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be

Enclosure PG&E Letter DCL-23-120 13 endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

4.2 Precedent The NRC has previously approved a 144-hour completion time for TS 3.7.8 Action A.1 to support replacement of the ASW Pump 1-1 motor during Unit 1 Cycle 23 in Amendment 238 for Unit 1 (Reference 2) based on PG&E Letters DCL-21-046 (Reference 2) and DCL-21-048 (Reference 3). The NRC approved the same additional Completion Time of 72-hours for TS 3.7.8 Required Action A.1 (total Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br />) for the same component, the ASW pump motor, in Reference 2.

The NRC technical conclusion found the 144-hour Completion Time acceptable based on the loss of one ASW pump, while in the proposed TS 3.7.8 Condition A Completion Time of 144-hours, remained bounded by the UFSAR accident analyses in that the remaining Operable ASW pump can provide the necessary heat removal function. This conclusion remains applicable since the OPERABLE Unit 2 ASW pump 2-1 can provide the necessary heat removal function.

The NRC staff further found the proposed change was not risk significant based on risk insights. This conclusion remains applicable since the risk insights using the DCPP PRA model, for the one-time 144-hour Completion Time proposed for TS 3.7.8 Condition A for Unit 2 Cycle 24, has been determined to not be risk significant.

4.3 No Significant Hazards Consideration Analysis PG&E has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, Issuance of amendment, as discussed below:

1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed change to the requirements in TS 3.7.8, Auxiliary Saltwater (ASW) System Condition A will allow a one-time Completion Time of 144-hours during Unit 2 Cycle 24 for Auxiliary Saltwater System (ASW) Pump 2-2 to support the emergent replacement of the pump motor. The ASW system is not an initiator of any UFSAR Chapter 6 or 15 design basis accident or event, and therefore, the proposed change does not increase the probability of any accident

Enclosure PG&E Letter DCL-23-120 14 previously evaluated. The ASW system is used to supply cooling water to respond to accidents that have been previously evaluated. The proposed change affects only the time allowed for an ASW system train to be inoperable and does not affect the design of the ASW system. With the change to TS 3.7.8, adequate ASW continues to be provided to perform the heat removal function for accidents previously evaluated and there is no significant impact on accident consequences. The proposed change does not significantly change how the plant would mitigate an accident previously evaluated.

Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different accident from any accident previously evaluated?

Response: No.

The proposed change does not result in a change in the manner in which the ASW system provides plant protection. The ASW system will continue to perform the function of heat removal while in the proposed revised TS 3.7.8 Condition A. The change does not involve a physical alteration of the plant that impacts the capability of the ASW system to perform its design function.

Therefore, the proposed change does not create the possibility of a new or different accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed change does not alter the manner in which safety limits, limiting safety system settings, or limiting conditions for operation are determined. The safety analysis acceptance criteria are not impacted by this change. The proposed change will not result in plant operation in a configuration outside the existing design basis since TS 3.7.8 Condition A already allows one train of the ASW system to be inoperable.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above evaluation, PG&E concludes that the proposed change does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and accordingly, a finding of no significant hazards consideration is justified.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Enclosure PG&E Letter DCL-23-120 15 Based on the above evaluation, PG&E concludes that the proposed change does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and accordingly, a finding of no significant hazards consideration is justified.

4.4 Conclusions In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5.

ENVIRONMENTAL CONSIDERATION PG&E has evaluated the proposed amendment and has determined that the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

6.

REFERENCES

1.

NUREG-0800 (Standard Review Plan), Chapter 19.2, Review of Risk Information Used to Support Permanent Plant-Specific Changes to the Licensing Basis: General Guidance, Appendix D, Use of Risk Information in Review of Non-Risk-Informed License Amendment Requests, June 2007.

2. NRC Letter Diablo Canyon Nuclear Power Plant, Unit 1 - Issuance of Amendment No. 238 RE: Revision to Technical Specification 3.7.8, Auxiliary Saltwater (ASW) System (Emergency Circumstances) (EPID L-2021-LLA-0123), dated July 8. 2021 (ADAMS Accession No. ML21188A345).
3. 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).

Enclosure PG&E Letter DCL-23-120 16

4. PG&E Letter 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,'

dated July 7, 2021 (ADAMS Accession No. ML21189A001).

5. PG&E Letter DCL-23-054, License Amendment Request 23-01, Revision to Technical Specifications to Adopt Risk-Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b,' dated July 13, 2023 (ADAMS Accession No. ML23194A228).

Enclosure PG&E Letter DCL-23-120 Proposed Technical Specification Change(s)

Remove Page Insert Page 3.7-16 3.7-16

ASW 3.7.8 DIABLO CANYON - UNITS 1 & 2 3.7 PLANT SYSTEMS 3.7.8 Auxiliary Saltwater (ASW) System LCO 3.7.8 Two ASW trains shall be OPERABLE.

APPLICABILITY:

MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One ASW train inoperable.

A.1

NOTE--------------

Enter applicable Conditions and Required Actions of LCO 3.4.6, RCS Loops - MODE 4, for residual heat removal loops made inoperable by ASW.

NOTE----------

A Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> is applicable for ASW pump 2-21-1 on a one-time basis, for Unit 21 cycle 2423.

Restore ASW train to OPERABLE status 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B. Required Action and associated Completion Time of Condition A not met.

B.1 Be in MODE 3.

AND B.2

NOTE-----------

LCO 3.0.4.a is not applicable when entering MODE 4.

Be in MODE 4.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 12 hours 3.7-16 Unit 1 - Amendment No. 135, 200, 219, 238, Unit 2 - Amendment No. 135, 201, 221,

Enclosure PG&E Letter DCL-23-120 Revised Technical Specification Page(s)

ASW 3.7.8 DIABLO CANYON - UNITS 1 & 2 3.7 PLANT SYSTEMS 3.7.8 Auxiliary Saltwater (ASW) System LCO 3.7.8 Two ASW trains shall be OPERABLE.

APPLICABILITY:

MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One ASW train inoperable.

A.1

NOTE--------------

Enter applicable Conditions and Required Actions of LCO 3.4.6, RCS Loops - MODE 4, for residual heat removal loops made inoperable by ASW.

NOTE----------

A Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> is applicable for ASW pump 2-2 on a one-time basis, for Unit 2 cycle 24.

Restore ASW train to OPERABLE status 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B. Required Action and associated Completion Time of Condition A not met.

B.1 Be in MODE 3.

AND B.2

NOTE-----------

LCO 3.0.4.a is not applicable when entering MODE 4.

Be in MODE 4.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 12 hours 3.7-16 Unit 1 - Amendment No. 135, 200, 219, 238, Unit 2 - Amendment No. 135, 201, 221,

Enclosure PG&E Letter DCL-23-120 Technical Specification Bases Change(s)

(For information only)

ASW B 3.7.8 DIABLO CANYON - UNITS 1 & 2 BASES (continued)

ACTIONS A.1 If one ASW train is inoperable, action must be taken to restore OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In this Condition, the remaining OPERABLE ASW train is adequate to perform the heat removal function. However, the overall reliability is reduced because a single failure in the OPERABLE ASW train could result in loss of ASW system function. The Note indicates that the applicable Conditions and Required Actions of LCO 3.4.6, "RCS Loops-MODE 4," should be entered if an inoperable ASW train results in an inoperable decay heat removal train. This is an exception to LCO 3.0.6 and ensures the proper actions are taken for these components. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is based on the redundant capabilities afforded by the OPERABLE train, and the low probability of a DBA occurring during this time period.

The 72-hour Completion Time is modified by a Note that allows a one-time Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> for ASW pump 2-21-1, for Unit 21 cycle 2423 to support emergent replacement of the ASW pump 2-21-1 motor. The one-time Completion Time of 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> is reasonable considering the capabilities of the other ASW Pump 2-11-2 to perform the heat removal function, the cross-tie capabilities of ASW from Unit 12, the low probability of a design basis accident occurring during this period, and the one-time use of a 144-hour Completion Time.

(continued)

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