LR-N18-0107, Response to Request for Additional Information, License Amendment Request Inverter Allowed Outage Time (AOT) Extension (Electrical Branch)

Response to Request for Additional Information, License Amendment Request Inverter Allowed Outage Time (AOT) Extension (Electrical Branch)

ML18291B053
Person / Time
Site:	Hope Creek
Issue date:	10/17/2018
From:	Carr E Public Service Enterprise Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LAR H18-02, LR-N18-0107
Download: ML18291B053 (7)

Text

PSEG Nuclear LLC P. 0. Box 2:36, Hancocks Bridge, New Jersey 08038-0236 PSEG Nudea:rLLC 10 CFR 50.90 LR-N18-01 07 LAR H18-02

7. 201R orS..TJ*uclear U. Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Hope Creek Generating Station Renewed Facility Operating License No. NPF-57 NRC Docket No. 50-354

Subject:

Response to Request for Additional Information, Re: License Amendment Request: Inverter Allowed Outage Time (AOT) Extension

References:

1. PSEG letter to NRC, "License Amendment Request: Inverter Allowed Outage Time (AOT) Extension" dated April 13, 2018 (ADAMS Accession No. ML18103A218)

2. NRC email to PSEG, "Hope Creek- Final RAI RE: Inverter AOT Extension,"

dated September 6, 2018 (ADAMS Accession No. ML18250A314)

In the Reference 1 letter, PSEG Nuclear LLC (PSEG) submitted a license amendment request for Hope Creek Generating Station. The proposed amendment would revise Technical Specifications to increase the Alternating Current (AC) Inverters allowed outage time (AOT) from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days. In Reference 2, the Nuclear Regulatory Commission (NRC) requested PSEG to provide additional information in order to evaluate the proposed License Amendment Request to revise Technical Specifications. The response due date was subsequently extended to October 19 , 2018 at PSEG's request. to this letter provides a restatement of the RAJ questions followed by our responses. PSEG has determined that the information provided in this submittal does not alter the conclusions reached in the 1 0 CFR 50.92 no significant hazards determination previously submitted. In addition, the information provided in this submittal does not affect the bases for conGiuding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.

There are no regulatory commitments contained in this letter.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b), PSEG is providing a copy of this response, with attachments, to the designated State of New Jersey Official.

Should you have any questions regarding this submittal, please contact Mr. Lee Marabella at 856-339-1208.

OCT 17 20*18 Page 2 10 CFR 50.90 LR-N18-0107 I declare under penalty of perjury that the foregoing is true and correct.

Executed on !0/7:?-

(Date)

Eric Carr Site Vice President Hope Creek Generating Station

Attachment:

1. Response to Request for Additional Information - License Amendment Request to Revise Technical Specification 3.8.3.1 Regarding Alternating Current Inverters cc: Administrator, Region I, NRC Mr. J. Kim, Project Manager, NRC NRC Senior Resident Inspector, Hope Creek Mr. P. Mulligan, Chief, NJBNE Hope Creek Commitment Tracking Coordinator Corporate Commitment Tracking Coordinator

LR-N18-0107 Attachment 1 Response to Request for Additional Information - License Amendment Request to Revise Technical Specification 3.8.3.1 Regarding Alternating Current Inverters 1

LR-N18-0107 By letter dated April 13, 2018 (Agencywide Documents Access management System (ADAMS)

Accession No. ML18103A218), PSEG Nuclear LLC (PSEG), requested an amendment to the Renewed Facility Operating License NPF-57 for Hope Creek Generating Station (HCGS) Unit 1.

The proposed license amendment request (LAR) would revise the Technical Specifications (TS) 3.8.3.1, Distribution - Operating, to increase the allowed outage time (AOT) for restoring inoperable alternate current (AC) inverter(s) to operable status from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days. By email dated September 6, 2018, the NRC staff requested additional information to complete the review of the LAR.

Below is a restatement of the questions followed by our responses.

Question 1 (EEOB RAI-1)

In the LAR, the licensee proposed to extend the AOT for restoring inoperable inverter (s) in one channel to operable status from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days, which is a 6-day extension. The licensee stated that the current 24-hour AOT can be insufficient in certain instances to support on-line troubleshooting, corrective maintenance, and post-maintenance testing in response to emergent issues. The licensee further states:

[if] the emergent issue had required complex troubleshooting or more extensive post-maintenance testing, or if backup, burnt in replacement components were not available on site, the process of returning the inverter to operable status could have taken more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The recommended burn-in period for replacement circuit cards is 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />.

In addition, the licensee stated that HCGS performs preventive maintenance on the safety related UPS units during each refueling outage and has no current plans to perform routine preventive maintenance on a scheduled basis at power. The licensee provided operating experience instances for inoperable inverters.

The NRC staffs guidance in BTP 8-8 for reviewing LARs for AOT extensions for electrical power sources states that the licensee must provide justification for the duration of the requested AOT (actual hours plus margin) based on plant-specific past operating experience.

The NRC staff notes that the inoperable inverters were returned to operable status within the existing 24-hour AOT in each of the HCGS operating experience instances, and the licensee did not provide a technical justification for the proposed extended AOT. Therefore, the NRC staff requests the following information:

Provide a discussion that details a technical justification for the proposed inverter AOT extension based on the HCGS plant-specific past operating experience and vendor recommendations for performing maintenance on the inverters.

Response

Plant-specific operating experience does not include instances in which more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> was required to return an inoperable inverter to operable status. However, as noted in the LAR, in one case an inoperable inverter was restored to operable status with less than seven hours before plant shutdown would have been required. Conditions that resulted in an unplanned inoperability of a required inverter were promptly identified, replacement parts were readily available and extensive post-maintenance testing and component tuning was not required. In any of the instances of unplanned inverter inoperability in the Hope Creek plant-specific 2

LR-N18-0107 operating experience, the current 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allowed outage time would likely have been exceeded if burned-in replacement parts had not been readily available, or if the emergent issue had required complex troubleshooting, or more extensive post-maintenance testing. The extended AOT will provide the time that would be required to properly develop and implement a troubleshooting plan; perform corrective maintenance, and complete operability testing in the event of an inverter failure that required complex troubleshooting or extensive component replacement.

In the event of an inverter failure that requires complex troubleshooting, the required time to resolve the issue could be well over the current 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allowable outage time. The inverter would first need to be tagged out by operations personnel in order to ensure the safety of both workers and the inverter. A multi-discipline troubleshooting team would have to be assembled consisting of maintenance, engineering, and operations personnel to diagnose and resolve the equipment malfunction. This team would then create a troubleshooting plan which requires a proper level of risk review and would be subject to independent challenge or possibly independent third party review before implementation. Once approved, the troubleshooting plan would then have to be executed through an emergent work order. This entire process of assembling a team, developing a plan, and planning the work order could realistically take over the current allowable 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> depending on the nature of the inverter failure. Following the work order planning, maintenance would need to implement the troubleshooting plan.

In the event that the failed component is an electrolytic capacitor, the possibility for multiple failed components due to short-circuit leading to leakage of electrolytes is possible. In this situation, the work that needs to be done to fix the inverter may require both the removal and replacement of circuit cards and capacitors, as well as a full cleaning of the inside of the cabinet of electrolyte residue. In order to perform the troubleshooting, plan a work order, and remove and replace failed cards and capacitors, this could take maintenance more than 5 complete shifts. After the replacement of the failed components, calibration of the gate cards is required.

Once the gate cards are calibrated, the next steps revolve around ensuring the inverter can be returned to service. De-energized tests on the inverter are to be performed in order to ensure proper maintenance was performed. Once the de-energized tests are complete, operations can release tags to energize the inverter. Once the inverter has warmed up, post maintenance energized testing must be performed as final check to ensure that the inverter can be returned to service.

A postulated timeline for failure of a Class 1E inverter [A-D]D48[1/2] is provided below.

Additional time could be required if corrective maintenance required replacement of cards for which burned-in spares were not immediately available:

Activity Activity duration (hours)

Assemble troubleshooting team 4 Staff outage control center (OCC) and review situation 4 Tag-out equipment 4 Develop complex troubleshooting plan 12 Plan troubleshooting work order 2 Implement troubleshooting plan 12 Plan corrective maintenance work order 4 Perform corrective maintenance 36 3

LR-N18-0107 Activity Activity duration (hours)

Calibrate gate cards 12 Perform de-energized test 12 Release tags 4 Energize inverter 2 Post maintenance test 8 Total duration 116 With the exception of air filter inspections and thermography, preventive maintenance is performed during refueling outages. There are no current plans to perform routine preventive maintenance on a scheduled basis at power. Should the need for such maintenance be identified as a result of component performance, the necessary preventive maintenance would be planned and scheduled in accordance with PSEG procedures for on-line work management.

Vendor recommended maintenance includes air filter inspections and cleaning (if necessary),

and periodic inspections and cleaning of the inverter, rectifier, static switch and regulator.

Cleaning and inspections are currently performed at 18 month interval for various uninterruptible power supply (UPS) components.

Question 2 (EEOB RAI 2)

LAR Section 2.1, System Design and Operation, states:

The Class 1E AC power system is designed to provide reliable source of power to all Class 1E loads in the plant. The system is divided into 4 channels (A, B, C, D). These loads are essential for safe and orderly shutdown of the plant, maintaining the plant in a safe condition, and mitigating the consequences of an accident. The loads are divided into 4 groups such that any combination of 3 out of the 4 groups has the ability to supply the minimum required safety loads to perform the above functions. The channels do not have load sharing ability. Each of these channels has two associated Class 1E 120 V

[volts] AC uninterruptable power supply (UPS) units. []

Each UPS is comprised of a static rectifier, a static inverter, a static switch assembly, and a regulated power supply.

The licensee provided a summary of the effects of an inverter failure on the plant safety systems, controls, and indications for each 120 V AC distribution panel fed by its associated inverter. The failure of each of the two inverters in a channel has different impacts on the plant.

The NRC staffs guidance in BTP 8-8 for reviewing LARs for AOT extensions for electrical power sources recommends the provision of a supplemental power source capable of performing the function of the inoperable equipment during the extended AOT. The NRC staff notes that the licensee did not discuss the provision of a supplemental power source during the extended AOT. To allow the NRC staff to evaluate the technical adequacy of the extended AOT for inoperable inverters, provide the following information:

In case another inverter would fail in a redundant channel during the proposed extended AOT for restoring inoperable inverters in one channel to operable status, provide a discussion that describes:

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LR-N18-0107

a. The plant response and the effects on the plant safety-related systems required to mitigate a design basis event (DBE) and their safety functions.

Response

In the event another inverter would fail in a redundant channel during the proposed extended AOT, the static switch shifts to the backup AC power supply (Class 1E 480V AC MCC powered from an MCC different than the one powering the UPS static rectifier),

if a loss of inverter output is indicated. Operating procedures provide direction for manual transfer to the backup AC power supply if required.

With the associated 120 VAC distribution panel energized from its backup Class 1E 480 VAC MCC via the voltage regulator, plant safety-related systems required to mitigate a design basis event (DBE) would remain OPERABLE. If failure of a second inverter while in the extended AOT resulted in loss of power to the associated 120 VAC distribution panel, plant response would be as described in section 2.1 of the LAR. In either case, having inverters in more than one channel inoperable would require entry into LCO 3.0.3 requiring action to be initiated within one hour to be in STARTUP within the next six hours, HOT SHUTDOWN within the following six hours and in COLD SHUTDOWN within the subsequent 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

For a design basis event (DBE), coincident with a loss of offsite power, the effects of another inverter failure in a redundant channel on the plant safety-related systems and their safety functions would depend upon which two inverters were inoperable. Any combination of inverter losses would be dealt with by their individual procedures on a priority basis.

b. The use of a supplemental 120 V AC power source such as a spare inverter or a UPS, the compensatory measures, equipment alignment, and the procedures in place to address the potential consequences to the plant in the event of a DBE or an anticipated operational occurrence if there would be a potential loss of safety functions or reduction in defense in depth of affected safety systems. If there is not a need to use a supplemental 120 V AC power source, please provide a justification.

Response

The Protected Equipment Program incorporates compensatory measures which control what equipment or systems will not be allowed to be taken out of service concurrent with one or both inverters in one channel out of service. With one or both inverters in one channel inoperable, the redundant inverters, instrument panels and emergency diesel generators in the redundant channels are protected. Inoperability of inverter [A-D]D481 does not prevent the associated EDG from starting automatically and re-energizing the associated 4160V AC bus. The associated EDG can also be manually started and loaded in accordance with existing operating procedures if required to restore power to a 120 VAC distribution panel. The operator response time program documents that an EDG can be transferred to local control well within the time recommended in BTP 8-8 for supplemental power sources. The time required to then start and load the EDG would not be expected to exceed the recommended time.

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