NMP2L2739, Request for Additional Information for Nine Mile Point Nuclear Station, Unit 2, to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b, Revision 2

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Request for Additional Information for Nine Mile Point Nuclear Station, Unit 2, to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b, Revision 2
ML20241A044
Person / Time
Site: Nine Mile Point Constellation icon.png
Issue date: 08/28/2020
From: David Gudger
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NMP2L2739
Download: ML20241A044 (12)
v • d • e


Text

200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.90 NMP2L2739 August 28, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410

Subject:

Request for Additional Information for Nine Mile Point Nuclear Station, Unit 2, to Adopt TSTF-505, "Provide Risk-Informed Extended Completion Times -

RITSTF Initiative 4b," Revision 2

References:

1. Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times -

RITSTF Initiative 4b," dated October 31, 2019

2. Letter from M. Marshall (Senior Project Manager, U.S Nuclear Regulatory Commission) to R. Reynolds (Exelon Generation Company, LLC), "Nine Mile Point Nuclear Station, Unit 2 - Supplemental Information Needed for Acceptance of Requested Licensing Action RE: Adoption of Risk-Informed Completion Times (EPID L-2019-LLA-0234), " dated December 5, 2019
3. Letter from S. Rafferty-Czincila (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Supplemental Information No.1 for Nine Mile Point Nuclear Station, Unit 2, to Adopt TSTF-505, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b,' Revision 2,"

dated December 12, 2019

4. Letter from M. Marshall (Senior Project Manager, U.S Nuclear Regulatory Commission) to R. Reynolds (Exelon Generation Company, LLC), "Nine Mile Point Nuclear Station, Unit 2 - Request for Additional Information RE:

Review of License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times (EPID L-2019-LLA-0234)," dated July 30, 2020

U.S. Nuclear Regulatory Commission Request for Additional Information TSTF-505, Risk-Informed Extended Completion Times Docket No. 50-410 August 28, 2020 Page 2 By letter dated October 31, 2019 (Reference 1), Exelon Generation Company, LLC (Exelon) requested to change the Nine Mile Point Nuclear Station, Unit 2 (NMP2) Technical Specifications (TS). The proposed amendment would modify TS requirements to permit the use of Risk Informed Completion Times in accordance with TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b," (ADAMS Accession No. ML18183A493).

In a letter dated December 5, 2019 (Reference 2), the NRC requested Supplemental Information to support their acceptance review of Reference 1. The acceptance review is performed to determine if there is sufficient information in scope and depth to allow the NRC staff to complete its detailed technical review. The letter states that bullets e and f of the proposed TS Administrative Section 5.5.15, "Risk Informed Completion Time Program,"

provided in Attachment 2 of Reference 1 differs from the wording in the NRC-approved TSTF-505, Revision 2 and that this variation is not identified nor justified in Reference 1.

This letter requests supplemental information to justify the variation. Exelon provided the supplemental information in Reference 3.

On July 30, 2020, the NRC provided a Request for Additional Information (RAI) to support their continued review of Reference 1. to this letter contains the NRCs request for additional information immediately followed by Exelons response. Attachment 2 provides the markup changes to Enclosure 1, Table E1-1. Attachment 3 provides the updated TS markup of page 3.3.5.1-3.

Exelon has reviewed the information supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in Reference 1. The supplemental information provided in this letter does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration.

Furthermore, the supplemental information provided in this letter does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.

There are no commitments contained in this response.

If you should have any questions regarding this submittal, please contact Ron Reynolds at 610-765-5247.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 28th day of August 2020.

U.S. Nuclear Regulatory Commission Request for Additional Information TSTF-505, Risk-Informed Extended Completion Times Docket No. 50-410 August 28, 2020 Page 3 Respectfully, David T. Gudger Sr. Manager, Licensing Exelon Generation Company, LLC : Response to Request for Additional Information : Revised Page E1-21 of Table E1-1 in Enclosure 1 : Revised TS Page 3.3.5.1-3 cc:

USNRC Region I Regional Administrator w/attachments USNRC Senior Resident Inspector - NMP USNRC Project Manager, NRR - NMP A. L. Peterson, NYSERDA

ATTACHMENT 1 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License NPF-69 Docket No. 50-410 Request for Additional Information Adopt Risk Informed Completion Times Response to Request for Additional Information

Response to Request for Additional Information Adopt Risk Informed Completion Times Page 1 of 4 Docket No. 50-410

RAI 1

Section 50.36(c) of 10 CFR requires TS to contain limiting conditions of operation (LCO) that describe the lowest functional capability of equipment required for safe operation of a plant. In Table E1-1 of Enclosure 1 of the LAR, the licensee lists each LCO to which the RICT Program is proposed to be applied and the design success criteria (DSC) for the LCO. In section 1 of, the licensee stated that the DSC is a summary of the success criteria from the design basis analyses.

The plants DSC are derived from the design basis analysis of the plant, as documented in the updated safety analysis report (USAR) and should include a minimum set of required equipment that has the capacity and capability to safely shut down the reactor in case of an accident and maintain it in a safe condition. NMP2 USAR, Section 8.1.4 states, in part:

The emergency ac [alternating current] power system is divided into three physically separate and electrically independent divisions designated Divisions I, II, and III. Any two out of these three divisions [have] the capacity and capability to safely shut down the reactor in case of a LOCA [loss of coolant accident] or any other DBA [design basis accident].

In Table E1-1 of Enclosure 1 of the LAR, the licensee stated that the DSC for TS LCO 3.8.1, Condition B, are one non-HPCS (high pressure core spray) emergency diesel generator (EDG).

However, in the LAR, the DSC for TS LCO 3.8.1.B are one non-HPCS EDG while the USAR states that two divisions of the AC power system are required to safely shut down the reactor.

Please explain this apparent discrepancy DSC in Table E1-1 of Enclosure 1 of the LAR and the Nine Mile Point USAR. Additionally, describe any effect the discrepancy may have on the PRA success criteria for TS LCO 3.8.1.B.

Exelon Response to RAI 1 USAR Section 8.1.4 states:

The emergency ac power system is divided into three physically separate and electrically independent divisions designated Divisions I, II, and III. Any two out of these three divisions has the capacity and capability to safely shut down the reactor in case of a LOCA or any other DBA. The physical separation and electrical independence of the three divisions are maintained through the distribution system under all conditions of plant operation. The three divisions are color coded for easy identification.

USAR Section 8.3.1.1.2:

In case of unavailability of any one diesel generator, the remaining two diesel generators will be capable of feeding all the loads necessary for safe shutdown of the unit in the event of any DBA and LOOP.

The Tech Spec Bases for 3.8.1 states:

These features are designed with redundant safety related divisions (i.e., single division systems are not included, although, for this Required Action, Division 3 (HPCS System) is considered redundant to Division 1 and 2 Emergency Core Cooling Systems (ECCS)). Redundant required features failures consist of

Response to Request for Additional Information Adopt Risk Informed Completion Times Page 2 of 4 Docket No. 50-410 inoperable features associated with a division redundant to the division that has no offsite power.

Based on the above information, the Design Success Criteria for TS 3.8.1.B in Table E1-1 is revised to state "Any two EDGs" instead of One of two Non HPCS EDGs. Also, the PRA Success Criteria for TS 3.8.1.A in Table E1-1 is revised to state "Same" as the HPCS EDG is explicitly credited in the Design Success Criteria. (see Attachment 2)

RAI 2

Section 50.36(c) of 10 CFR requires TS to contain limiting conditions of operation (LCO) that describe the lowest functional capability of equipment required for safe operation of a plant. In Table E1-1 of Enclosure 1 of the LAR, the DSC for TS LCO 3.8.1.C (two required offsite circuits inoperable) is one offsite source. The NRC staff notes that the programs condition description for TS 3.8.1.C is, "[t]wo offsite circuits inoperable." If both offsite circuits are inoperable, one offsite source, as listed in the DSC, cannot provide the necessary power to shutdown the reactor and maintain it in safe condition. Therefore, it is not clear how one offsite circuit can be the DSC for TS 3.8.1.C during the RICT program entry.

Please explain this apparent discrepancy in Table E1-1 of Enclosure 1 of the LAR. Additionally, describe any effect the discrepancy may have on the PRA success criteria for TS LCO 3.8.1.C.

Exelon Response to RAI 2 In the event of a loss of both offsite power sources (both offsite circuits inoperable), the Engineered Safety Features (ESF) electrical loads are automatically connected to the Diesel Generators in sufficient time to provide for safe reactor shutdown and to mitigate the consequences of a Design Basis Accident (DBA) such as a LOCA. Certain required plant loads are returned to service in predetermined sequence in order to prevent overloading the Diesel Generators.

The ESF systems of any two of the three divisions provide for the minimum safety functions necessary to shut down the unit and maintain it in a safe shutdown condition.

The OPERABILITY of the AC electrical power sources is consistent with the initial assumptions of the accident analyses and is based upon meeting the design basis of the unit. This includes maintaining the onsite or offsite AC sources OPERABLE during accident conditions in the event of an assumed loss of all offsite power or all onsite AC power; and a worst-case single failure.

Table E1-1 regarding TS 3.8.1.c incorrectly references See 3.8.1.A. This table section is revised as appropriate (see Attachment 2).

RAI 3

As part of its evaluation, the NRC staff reviews the proposed risk management action (RMA) examples for reasonable assurance that the RMAs are considered to monitor and control risk and to ensure adequate defense-in-depth. Enclosure 12 of the LAR describes the RMAs examples for TS 3.8.1.A, TS 3.8.1.B, TS 3.8.1.D, and TS 3.8.4.A. However, the LAR does not include the RMA examples for TS 3.8.1.C, TS 3.8.7.A, TS 3.8.8.A, TS 3.8.8.B, and TS 3.8.8.C.

Response to Request for Additional Information Adopt Risk Informed Completion Times Page 3 of 4 Docket No. 50-410 Please provide RMA examples for TS 3.8.1.C, TS 3.8.7.A, TS 3.8.8.A, TS 3.8.8.B and TS 3.8.8.C.

Exelon Response to RAI 3 TS 3.8.1.C - This TS is for both offsite sources inoperable. As such, the same RMA examples provided for TS 3.8.1.A would apply with the exception of grid-related and switchyard RMAs which do not apply with two offsite lines inoperable. Additional RMA examples to reduce the magnitude of the risk increase for both offsite sources inoperable could include:

Maximize and protect the remaining capability of the offsite sources.

Protect RCIC and HPCS Defer activities that could increase the likelihood of a plant trip.

TS 3.8.7.A -The same RMA example as 3.8.1.D is applied to TS 3.8.7.A. The UPS system is comprised of two UPS per division with one required. They are operable when powered from either the AC or DC source as long as the DC source is operable per the Bases. Therefore, the same RMA for 3.8.1.D is applied to the scenario with the UPS inoperable.

3.8.8.A - For one or both Division 1 and 2 AC electrical power distribution subsystems inoperable -the same RMA as 3.8.1.D are applied.

3.8.8.B - For one or both Division 1 and 2 120 VAC uninterruptible electrical power distribution subsystems inoperable -the same RMA as 3.8.1.D are applied based on the same rationale provided above for 3.8.7.A.

3.8.8.C - One or both Division 1 and 2 DC electrical power distribution subsystems inoperable -

the same RMA as TS 3.8.4.A is applied as they are both for the divisional DC busses.

RAI 4

In the LAR, the licensee stated that the proposed amendment is consistent with TSTF-505, Revision 2. In Section 2.3 of Attachment 1 of the LAR, the licensee lists the variations from TSTF-505, Revision 2. The TSTF contain model LCOs. Section 50.36(c) of 10 CFR requires TS to contain LCOs that describe the lowest functional capability of equipment required for safe operation of a plant.

For the required action of "Restore one [required] offsite circuit to OPERABLE status" for the condition "Two [required] offsite circuits inoperable," the completion time is "24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />." In the LAR the completion time is "24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> from discovery of both HPCS and Low-Pressure Core Spray (LPCS) Systems with no offsite power." The NRC staff notes that this difference appears to be a variation. The apparent variation between TSTF-505 and the NMP2 proposal is that the NMP2 TS requires restoration of one offsite circuit within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> from discovery of both HPCS and LPCS systems without offsite power. The LAR does not address the apparent variation.

Please provide a discussion of the difference and how it is implemented into the RICT program.

Response to Request for Additional Information Adopt Risk Informed Completion Times Page 4 of 4 Docket No. 50-410 Exelon Response to RAI 4 The following is a variation to TSTF-505, Revision 2 TS 3.8.1, AC Sources-Operating, Required Action A.3: The current Unit 2 TS addresses the multiple electrical alignments available for the HPCS system which is allowed to be aligned to either offsite circuit Line 5 or offsite circuit Line 6. LPCS can only be aligned to Line 5.

Depending upon which offsite circuit is lost and the alignment of the HPCS system, either or both systems may be impacted. The 24-hour required Completion Time places the additional restriction into the TS to recognize the potential to lose offsite capability for both injection systems simultaneously. This unique system design characteristic is a variance from the standard BWR/4 and BWR/6 design and therefore is a variation to TSTF-505, Revision 2.

The PRA fully models these alignments and is capable of calculating a RICT in the event LPCS and HPCS are without AC power.

RAI 5

Section 50.36(c) of 10 CFR requires TS to contain limiting conditions of operation that describe the lowest functional capability of equipment required for safe operation of a plant. TSTF-505, Revision 2 (ADAMS Accession No. ML18183A493), does not allow for TS loss of function conditions (i.e., those conditions that represent a loss of a specified safety function or inoperability of all required trains of a system required to be operable) in the risk informed completion time program.

There appears to be an error in the logical connector for the note for LCO 3.3.5.1, "ECCS -

Instrumentation," Action B.3.1 in that the note should apply only to the 24-hour completion time.

Therefore, the "OR" should be indented instead of what is currently proposed (where the "OR" would apply to both the 12-hour and 24-hour completion times). If the "OR" applies to the 12-hour completion time, based on the design success criteria provided in the license amendment request, it appears that this LCO action may constitute a loss of function.

a) Clarify whether the "OR" applies to both the 12-hour and 24-hour completion times or just the 24-hour completion time.

b) If the "OR" does apply to the 12-hour completion time, provide the technical basis for why the action does not constitute a loss of function.

Exelon Response to RAI 5 a) The "OR" applies to the 24-hour Completion Time. Markup of TS page 3.3.5.1-3 is revised to indent the "OR" appropriately to only apply to the 24-hour Completion Time (see Attachment 3).

b) The "OR" does not apply to the 12-hourCompletion Time. See the response to a) above and Attachment 3.

ATTACHMENT 2 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License NPF-69 Docket No. 50-410 Request for Additional Information Adopt Risk Informed Completion Times Revised Page E1-21 of Table E1-1 in Enclosure 1

Request IRU$GGLWLRQDO,QIRUPDWLRQ Adopt Risk Informed Completion Times TSTF-505 Docket No. 50-410 List of Revised Required Actions to Corresponding PRA Functions E1-21 Table E1-1: In Scope TS/LCO Conditions to Corresponding PRA Functions Technical Specification (TS)

TS Condition Description SSCs Covered by TS LCO Condition SSCs Modeled in PRA?

Function Required by TS LCO Condition Design Success Criteria PRA Success Criteria Other Comments 3.8.1.B One required DG inoperable.

2 EDGs and HPCS EDG Yes Supply AC loads when offsite power is lost

$Q\\WZR('*V Same SSCs are modeled consistent with the TS scope and so can be directly included in the RTR tool for the RICT program. The success criteria are consistent with the design basis.

3.8.1.C Two required offsite circuits inoperable.

3.8.1.D One required offsite circuit inoperable AND One required DG inoperable.

3.8.4.A Division 1 or 2 DC electrical power subsystem inoperable.

Two Battery chargers and one battery per division Yes Supply DC loads during operation One of two subsystems Same SSCs are modeled consistent with the TS scope and so can be directly included in the RTR tool for the RICT program. The success criteria are consistent with the design basis.

Lines 5/6 Yes Supply AC loads during operation ESF Electrical loads automatically connected to the EDGs Same Offsite Lines 5/6 and 2 EDGs and HPCS EDG Yes Supply AC loads during operation Same 2QHRIIVLWH6RXUFH

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E1-21 SSCs are modeled consistent with the TS scope and so can be directly included in the RTR tool for the RICT Program. The success criteria are consistent with the design basis.

ATTACHMENT 3 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License NPF-69 Docket No. 50-410 Request for Additional Information Adopt Risk Informed Completion Times Revised TS Page 3.3.5.1-3

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Not applicable when trip capability is not maintained.

In accordance with the Risk Informed Completion Time Program

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