W3F1-2024-0012, Response to NRC Integrated Inspection Report 05000382/2023004
| ML24071A185 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 03/11/2024 |
| From: | Sullivan J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, NRC Region 4, Document Control Desk |
| References | |
| W3F1-2024-0012 | |
| Download: ML24071A185 (1) | |
Text
E) entergy Joseph C. Sullivan Site Vice President Waterford Steam Electric Station, Unit 3 504-739-6660
March 11, 2024
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Response to NRC Integrated Inspection Report 05000382/2023004 Waterford Steam Electric Station, Unit 3 NRC Docket No. 50-382 Renewed Facility Operating License No. NPF-38
Reference:
Letter dated February 12, 2024, from John L. Dixon (NRC) to Joseph Sullivan (Entergy), Waterford Steam Electric Station, Unit 3 - Integrated Inspection Report 05000382/2023004
The purpose of this letter is to provide the Entergy Operations, Inc. (Entergy) response to the Waterford Steam Electric Station, Unit 3 Non-Cited Violation (NCV) 2023004-03 contained in the referenced letter. This NCV stated that the licensee's failure to ensure the starting batteries for the FLEX N and FLEX N+ 1 diesel generators had sufficient capacity to perform their functions was a violation of 10 CFR 50.155(b}(1 ). It is Entergy's position that this violation should be withdrawn based on the response to the NCV in the enclosure to this letter. The enclosure to this letter contains a restatement of the NCV and provides Entergy's response to the NCV.
This letter contains no new Regulatory Commitments. Should you have any questions concerning the content of this letter, please contact John Twarog, Regulatory Assurance Manager at 504-739-6747.
Respectfully,
Joseph C. Sullivan
Enclosure:
Response to NRC Integrated Inspection Report 05000382/2023004 Non-Cited Violation 2023004-03
cc: NRC Region IV Regional Administrator Director, Office of Enforcement Senior Resident Inspector, Waterford Steam Electric Station, Unit 3 Enclosure
W3F1-2024-00012 Response to NRC Integrated Inspection Report 05000382/2023004 Non-Cited Violation 2023004-03 W3F1-2024-0012 Enclosure Page 1 of 6
Response to NRC Integrated Inspection Report 05000382/2023004 Non-Cited Violation 2023004-03
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Background===
The Waterford Steam Electric Station, Unit 3 (Waterford 3) - Integrated Inspection Report 05000382/2023004 dated February 12, 2024 contained a Non-Cited Violation for failure to ensure the starting batteries for the FLEX N and FLEX N+ 1 diesel generators had sufficient capacity to perform their functions - NCV 05000382/2023004-03. This report stated, in part:
The inspectors reviewed a self-revealed Green finding and associated NCV of 10 CFR 50.155(b)(1), which states, in part, strategies and guidelines to mitigate beyond -design-basis events from natural phenomena must be capable of being implemented site-wide and must include maintaining or restoring core cooling capabilities. Specifically, from approximately February 14 to May 16, 2023, the licensee failed to ensure the starting batteries for the FLEX N and N+ 1 diesel generators had sufficient capacity to perform their required functions.
Description:
As part of the licensee's phase 2 strategies as required by NRG Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," the licensee committed to the guidance described in NE/ 12-06, "Diverse and Flexible Coping Strategies (FLEX)
Implementation Guide," revision 0. NRG Order EA-12-049 has since been codified by 1 O CFR 50. 155, "Mitigation of beyond-design-bas_is events."
Specifically for FLEX AC power supply, the licensee developed mitigating strategies that utilize a FLEX N diesel generator as a 480V power supply that can be hooked up into a safety bus. A FLEX N+ 1 diesel generator was stored outside the protected area as a backup that can be brought into the protected area and connected into a safety bus. These two diesel generators are the only dedicated means of providing 480V power for a beyond-design-basis station blackout event. The diesel generators are started by a set of two commercial 80 batteries for each generator.
On May 6, 2023, power was lost for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to the FLEX N+ 1 building which maintains the FLEX N+ 1 diesel generator starting battery charge. On May 13, 2023, the licensee was performing weekly rounds when it was identified the control panel of the FLEX N+ 1 diesel generator had no power. The capacity of the batteries was too low to restart the battery charger to provide the float charge. The batteries would not have had the capacity to start the FLEX N+ 1 diesel generator if needed. On May 14, 2023, the degraded starting batteries were replaced with the charged and ready set of spare FLEX starting batteries.
On May 16, 2023, the licensee removed power to the FLEX N diesel generator for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for maintenance. The power was reconnected 24 minutes later, and the licensee attempted to start the FLEX N diesel. However, the generator failed to start due to degraded capacity of the starting battery. In both failures, the cause was a starting battery that had degraded capacity. Because there was a set of ready spare batteries that would be able to be changed out in an actual event, the function of the FLEX AC power supply was not considered fully lost. All FLEX functions could still be completed within the time allotted.
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The licensee makes plans to replace the starting batteries on a 4-year frequency.
No tests are performed specifically on the batteries to ensure their capacity is adequate beyond performing a start of the FLEX N and FLEX N+ 1 diesel generators every six months. Both sets of starting batteries were purchased and installed in May 2020. There is no expected lifetime of the battery provided by the manufacturer. The warranty on the batteries is for 6 months with a pro-rated replacement that extends until 30 months of life. As evidenced by the failure to start of the diesel generators, the capacity of these starting batteries was degraded beyond the ability to start the FLEX diesel generators.
The date on which the starting batteries had degraded to no longer be functional is unable to be determined with accuracy. The degradation mechanism is not able to be identified on the licensee weekly or monthly checks of the equipment. The previous successful surveillances that started the FLEX N and N+ 1 diesel generators were on November 15, 2022. The inspectors assume the degradation occurred halfway from the last successful surveillance to when both FLEX diesel generators were repaired. This date was determined to be February 14, 2023.
Performance Assessment:
Performance Deficiency: The licensee failed to maintain mitigation strategies for beyond-design basis external events.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Equipment Performance attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the licensee failed to maintain the FLEX N and FLEX N+ 1 diesel generator batteries so their respective generators could start and provide power in accordance with the licensee mitigating strategies.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, "The Significance Determination Process (SOP) for Findings At Power." Using Exhibit 2, "Mitigating Systems Screening Questions," Section E, the inspectors determined the finding to be of very low safety significance (Green),
because the performance deficiency was associated with equipment not solely purposed for spent fuel pool instrumentation or for containment venting, but it was associated with equipment credited in a Phase 2 FLEX strategy such that all FLEX functions could still be completed in accordance with existing plant procedures within the time allotted.
Enforcement:
Violation: 10 CFR 50.155(b)(1), states, in part, strategies and guidelines to mitigate beyond-design-basis events from natural phenomena must be capable of being implemented site-wide and must include maintaining or restoring core cooling capabilities.
W3F1-2024-0012 Enclosure Page 3 of 6
Contrary to the above, from approximately February 14 to May 16, 2023, the licensee failed to maintain mitigation strategies for beyond-design basis external events. Specifically, the licensee failed to maintain the FLEX N and FLEX N+ 1 diesel generator batteries so their respective generators could start and provide power in accordance with the licensee mitigating strategies.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Entergy's Position
While the facts surrounding the events in May 2023 are stated accurately in the inspection report, the existence of a Performance Deficiency for the failure to ensure the starting batteries for the FLEX N and FLEX N+ 1 diesel generators had sufficient capacity to perform their functions is contested.
Since the industry-wide implementation of NEI 12-06, it has been widely discussed throughout the industry that an occurrence of a non-start of a FLEX diesel generator due to battery failure does not constitute a failure of that equipment to perform its function. The function of the equipment necessary to perform the required FLEX function (that of the diesel generator) was not compromised. The ability to start the diesel generator was degraded, but the functionality of the diesel generator was not in question and met the required timeline. Batteries are considered FLEX-support equipment and are not subject to the requirements of the EA-12-049 (and now codified in 1 O CFR 50.155) equipment necessary to support the Phase 2 strategies.
With the diverse and flexible solutions offered in the FLEX programs, the ability to jump, swap, or replace a battery immediately is within the design of the Final Integrated Plan for FLEX implementation, is considered a "skill of the craft," and does not need to be part of a procedure.
While some utilities have chosen to provide procedural guidance in the event a battery is not able to start a diesel generator, that is not required.
It is important to note that the FLEX equipment necessary to mitigate the beyond-design-basis external event was still functional. In fact, the inspection report clearly states that:
Because there was a set of ready spare batteries that would be able to be changed out in an actual event, the function of the FLEX AC power supply was not considered fully lost. All FLEX functions could still be completed within the time allotted.
Final Integrated Plan Expectations Maintained By letter dated, July 21, 2016, Waterford 3 notified the NRC of full compliance with EA-12-049.
In that letter, Waterford 3 states that the FLEX diesel generator is placed in service by 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> following the event. A detailed sizing calculation had been performed and its results indicate that the sizing of the diesel generator was acceptable for providing power to the necessary FLEX loads. The Waterford 3 commitment to having a functional diesel generator in service within the required time was maintained. The ability of the batteries to start the diesel generator does not impact the ability of the diesel generator, when started, to perform its function. In keeping with the overall expectation of the original Order and the current regulation, a licensee has the ability and expectation for "FLEXible" and reasonable means to be used to accomplish the Mitigating Strategies for a Beyond Design Basis External Event. The events cited in the inspection report meet that expectation. As a result, the Waterford 3 Final Integrated Plan was not degraded. No additional measure, other than those which would have met the expectation of the framers of NEI 12-06, would have been necessary.
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EPRI Preventative Maintenance Basis for FLEX Equipment Not Applicable In an effort to provide preventative maintenance guidance for use by licensee for plant equipment, in 1996 - long prior to the Fukushima event - the industry developed the EPRI Preventive Maintenance Basis Database (PMBD). This database continues to assist licensees in providing effective maintenance for nuclear power plants. Following the Fukushima event, the PMBD, along with the Expert Panel Workshop Process, was used to develop the "EPRI Preventative Maintenance Basis for FLEX Equipment." This is commonly referenced as the "EPRI FLEX PM Templates" or "PM Templates" or "EPRI guidance 1." These guidelines contain maintenance task contents, task interval recommendations, and a synopsis of the associated technical basis for many major components used in FLEX implementation. While the PMBD does have experience-based information and recommendations for battery maintenance, the EPRI FLEX PM Template refers to batteries and battery chargers as "supporting equipment." It is widely recognized that the expectation to maintain the equipment necessary to meet to the FLEX Mitigating Strategies was the intended target of the EPRI FLEX PM Template.
NEI 12-06, Section 11.5.2 states, "equipment that directly performs ( emphasis added) a FLEX mitigation strategy for the core, containment, or SFP should be subject to maintenance and testing guidance provided in INPO AP 913, Equipment Reliability Process, to verify proper function. The maintenance program should ensure that the FLEX equipment reliability is being achieved. Standard industry templates (e.g., EPRI) and associated bases will be developed to define specific maintenance and testing." The diesel generators, and not the supporting batteries, directly perform the function. As a result, the diesel generators are subject the maintenance requirements and not the batteries.
Over the last several years, failing starting batteries which support FLEX equipment have occurred at multiple stations. EPRI Operating Experience Bulletin (OEB)21-002 was issued to address this and to aid in the understanding of what constitutes FLEX equipment functionality.
This OEB provided a generic functionality assessment for FLEX equipment with starting battery failures. It states:
The supported piece of FLEX equipment should be considered non-functional if the starting battery is incapable of starting the supported piece of FLEX equipment unless the conditions described below are met for declaring the supported piece of FLEX equipment Functional but degraded. The supported piece of FLEX equipment may be considered Functional but degraded if the following conditions apply:
- An alternate means of starting the supported piece of FLEX equipment is available - e.g, jumper cables, spare batteries, jump packs.
- There is sufficient time to perform the recovery actions to start the supported FLEX equipment within the time allotted to successfully implement the associated FLEX strategy - e.g., margin is available between the time required and the expected performance validation time for the action such as using the supported FLEX pump to provide core cooling or the supported FLEX generator to provide electrical power.
Other considerations were also discussed in the OEB. It further states that, "(p)ersonnel performing jumpstart actions should be capable of doing so either as a skill of the craft action or written actions directed in procedures or guidelines."
1 NRC Operating Experience Smart Sample (OpESS) 2020/01 for IP 71111.XX and IP 71152.
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In consideration of the overarching requirement for the FLEX equipment to meet its function in the required timeline, the equipment skid itself and the supporting components for the FLEX equipment are important and should be maintained (including the batteries). However, these supporting components and the associated maintenance for them is outside the scope of that which is necessary to ensure the capacity and capability of the FLEX equipment, provided the overarching requirement can be met. Easily corrected issues like this do not, by itself, result in a Performance Deficiency.
Regulatory Requirements Maintained 10 CFR 50.155(b)(1) requires that strategies and guidelines to mitigate beyond-design-basis external events from natural phenomena be capable of being implemented. In this case, the equipment used to mitigate a Beyond Design Basis External Event is that of the FLEX diesel generator. The functionality of either the FLEX Nor the FLEX N+1 diesel generator will accomplish the strategy. The diesel generators are appropriately tested and maintained to ensure their function. Again, as stated in the inspection report, "(b)ecause there was a set of ready spare batteries that would be able to be changed out in an actual event, the function of the FLEX AC power supply was not considered fully lost. All FLEX functions could still be completed within the time allotted." As a result, no violation of 1 O CFR 50.155(b)(1) occurred.
Even if Waterford 3 had been faced with a flooding event as a part of a Beyond Design Basis External Event and the FLEX N+ 1 storage building where the spare batteries are stored was not easily accessible, other batteries on the 21' elevation could have been used to start the FLEX N Diesel Generator. The two batteries, one for the Diesel Driven Air Compressor and one for the FLEX Water Transfer Pump, would have been adequate.
Performance Deficiency Does Not Exist As stated in the inspection report, the Performance Deficiency was: "The licensee failed to maintain mitigation strategies for beyond-design basis external events." At no time during the events described in the inspection report did Waterford 3 fail to maintain its mitigation strategies for Beyond Design Basis External Events. The diesel generators were functional and, again as stated in the inspection report, "(a)II FLEX functions could still be completed within the time allotted."
The failure to maintain the FLEX N and FLEX N+ 1 diesel generator batteries is NOT the same as the failure to maintain the FLEX N and FLEX N+ 1 diesel generators. The diesel generators are the equipment that must be maintained as functional. With no Performance Deficiency, the use of IMC 0609, Appendix A, Exhibit 2 is not necessary or appropriate.
Batteries Maintained Appropriately On April 18, 2023, the Maintenance Work Orders (verifications/inspections) were performed on both the FLEX N and FLEX N+ 1 diesel generators. These inspections included ensuring that the supporting batteries for the FLEX equipment had clean tops and tight connections. The Battery Charging Systems were also checked to ensure they were working properly, and the charger voltages were recorded. It is appropriate to consider these Work Orders to be failure detection activities. While the battery failures in May 2023 were earlier than expected, the replacements were appropriately performed.
Since May 2023, the procedures for maintenance of FLEX batteries have been further enhanced to include specific instructions for failed batteries and battery testing; however, it is stressed that these enhancements were not necessary to meet the regulatory requirements of 10 CFR 50.155.
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Technical Requirement Manual <TRM) Requirements Maintained Waterford 3 TRM Section 3.13.2 requires the continued functionality of certain FLEX equipment.
If the FLEX Diesel Generator (FLEXMDSG001) in the Reactor Auxiliary Building is non functional, actions are required to be initiated to restore that equipment within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, implement compensatory measures for "N" capability within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and restore the equipment within 45 days. Similarly, if the FLEX Diesel Generator (FLEXMDSG002) in the 'N+1' Building is non-functional, it is required to be restored within 45 days. Although the ACTION statement was conservatively entered when the batteries were found to be degraded, the equipment itself continued to meet the surveillance requirements.
Conclusion The damage at the Fukushima Dai-ichi facility in 2011 caused by the Great Tohoku Earthquake and resulting tsunami in Japan was extensive, by all accounts. The NRC and the nuclear industry took significant action to enhance the safety of reactors in the United States based on the lessons learned from that accident. Embodied in those actions for licensees to plan for Beyond Design Basis External Events was always, and continues to be, the flexibility that may need to be taken. In fact, the term FLEX was not an acronym - it was used continuously by both the NRC and the industry to propagate the need for FLEXibility.
During the development of the response to EA-12-049, there was a recognition by the NRC management of the Japan Lessons Learned Project Directorate (JLD) that batteries were easily replaced. The stated requirement expressed by the JLD was that licensees could meet their Final Integrated Plan expectations within the required timeline. The NRC reviewed Revision O of NEI 12-06 and endorsed it in JLD-ISG-2012-01 as a process the NRC considered acceptable for meeting the regulatory requirements with noted clarifications.2 Throughout the revisions to NEI 12-06, it has been widely discussed throughout the industry, and with the NRC, that a battery failure does not constitute a failure of the equipment necessary to implement the FLEX strategy.
Considering the fact that FLEX equipment is commercial grade equipment and not safety related, it is important to remember that the same rigor and procedural guidance applicable to existing plant equipment is not necessary, expected nor appropriate. The proper capacity, capability, maintenance, and protection of FLEX equipment was driven by an NRC Order and resulting codification in 10 CFR 50.155; however, expending extraordinary resources, beyond those that the framers of NEI 12-06 intended, is not prudent and not in keeping with risk informed regulation.
For the issue at Waterford 3, the function of the equipment necessary to perform the required FLEX function (that of the diesel generator) was not compromised. The ability to start the diesel generator was degraded, but the functionality of the diesel generator was not in question and met the required timeline. Batteries are considered FLEX-support equipment and are not subject to the capability and capacity requirement of 1 O CFR 50. 155. With the diverse and flexible solutions offered in the FLEX programs, the ability to jump, swap, or replace a battery immediately is within the design of the Final Integrated Plan for FLEX implementation, is considered a "skill of the craft," and does not need to be part of a procedure. As a result, Entergy contends that no Performance Deficiency exists and the NCV, as written, should be withdrawn.
2 NRC Regulatory Guide 1.226, Revision O (June 2019), p.5.