ML22151A009

NRR E-mail Capture - Request for Additional Information Re Sequoyah Nuclear Plant Alternative Request RV-02

ML22151A009
Person / Time
Site:	Sequoyah
Issue date:	05/26/2022
From:	Kimberly Green Plant Licensing Branch II
To:	Taylor A Tennessee Valley Authority
References
L-2022-LLR-0034
Download: ML22151A009 (6)

Text

From:

Green, Kimberly Sent:

Thursday, May 26, 2022 4:12 PM To:

Taylor, Andrew Charles Cc:

Wells, Russell Douglas; Buckberg, Perry

Subject:

Request for Additional Information re Sequoyah Nuclear Plant Alternative Request RV-02 (EPID L-2022-LLR-0034)

Attachments:

Sequoyah RV-2 PIV RAIs L-2022-LLR-0034 5-26-22.pdf

Dear Mr. Taylor,

By letter dated March 15, 2022 (ADAMS Accession No. ML22074A315), the Tennessee Valley Authority (TVA) submitted Alternative Request RV-02 for the Sequoyah Nuclear Plant, Units 1 and 2, to allow operation for 1 cycle if certain pressure isolation valves undergo mechanical agitation as a means to achieve acceptable valve seat leakage.

The U.S. Nuclear Regulatory Commission (NRC) staff is reviewing your submittal and has identified areas where additional information is needed to complete its review. A draft request for additional information (RAI) was previously transmitted to you by email dated May 20, 2022.

At TVAs request, a clarification call was held on May 26, 2022, to clarify the NRC staffs draft RAI. As a result of the clarification call, the following changes were made the RAI:

EMIB-RAI-1(b) was revised to add, general design, including thecurrent EMIB-RAI-2(a) was revised to remove the word operating and replace it with the word any EMIB-RAI-4(a) was revised to add, ifexperienced any subsequent physical damage or degradation after and in an attempt to control leakage was deleted.

EMIB-RAI-4(b) was revised to change the term credible potential to reasonable potential EMIB-RAI-6 was revised to add leakbefore they are disassembled and inspected EMIB-RAI-9 was corrected to refer to Sequoyah Unit 2 in two places As agreed during the call, a response to the attached RAI is requested by June 30, 2022.

The NRC staff considers that timely responses to RAIs help ensure sufficient time is available for staff review and contribute toward the NRCs goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact Perry Buckberg at (301) 415-1383 or via email at Perry.Buckberg@nrc.gov.

On behalf of Perry Buckberg, Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Hearing Identifier:

NRR_DRMA Email Number:

1653 Mail Envelope Properties (DM6PR09MB5462F473562C512351533FEE8FD99)

Subject:

Request for Additional Information re Sequoyah Nuclear Plant Alternative Request RV-02 (EPID L-2022-LLR-0034)

Sent Date:

5/26/2022 4:11:32 PM Received Date:

5/26/2022 4:11:00 PM From:

Green, Kimberly Created By:

Kimberly.Green@nrc.gov Recipients:

"Wells, Russell Douglas" <rdwells0@tva.gov>

Tracking Status: None "Buckberg, Perry" <Perry.Buckberg@nrc.gov>

Tracking Status: None "Taylor, Andrew Charles" <actaylor@tva.gov>

Tracking Status: None Post Office:

DM6PR09MB5462.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 2088 5/26/2022 4:11:00 PM Sequoyah RV-2 PIV RAIs L-2022-LLR-0034 5-26-22.pdf 96085 Options Priority:

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REQUEST FOR ADDITIONAL INFORMATION REGARDING ALTERNATIVE REQUEST RV-02 PRESSURE ISOLATION VALVE LEAKAGE TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 and 50-328 EPID-L-2022-LLA-0034 References

1.

Letter from Tennessee Valley Authority [TVA] to U.S. Nuclear Regulatory Commission (NRC), Sequoyah Nuclear Plant (SQN), Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RV-02, dated March 15, 2022 (ADAMS Accession No. ML22074A315).

2.

Summary of February 16, 2022, public pre-application meeting with Tennessee Valley Authority regarding a future submittal of a request for an alternative to requirements for addressing Pressure Isolation Valve Leakage (ADAMS Accession No. ML22048B785).

Regulatory Basis The SQN Units 1 and 2 Inservice Testing Program implements the American Society of Mechanical Engineers (ASME) Operation and Maintenance Code as required by SQN Units 1 and 2 Technical Specification 5.5.6, Inservice Testing Program, and Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(f). Subsection ISTC-3630 of the SQN Units 1 and 2 Operation and Maintenance Code of record requires PIV testing to verify their seat leakages within acceptable limits and states, Valve closure before seat leakage testing shall be by using the valve operator with no additional closing force applied. In accordance with 10 CFR 50.55a(z)(2), the NRC staff may authorize an alternative to an ASME Code requirement if the licensee demonstrates that the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Requests for Additional Information EMIB-RAI-1 Alternative Request RV-02,Section V, in the subsection Summary, first paragraph, states:

The proposed alternative would permit continued startup if the PIV [pressure isolation valve] could be demonstrated to have acceptable seat leakage following mechanical agitation. The valve would only be acceptable for normal operation for one cycle and only if the final PIV seat leakage met the TS [Technical Specification] leakage criteria. This alternative will apply to ISTC-3630 requirements as they relate to use of additional closing force to achieve PIV closure before seat leakage testing, ISTC-3630(f) requirements as they relate to corrective action following a failed seat leakage test, ISTC-5221(a)(1) requirements as they relate to demonstrating that a PIV check valve disc travel to its seat following cessation of flow, and ISTC-5224 requirements as they relate to retesting following any required corrective action before the valve is returned to service.

The licensee is requested to provide the following information:

(a)

Clarify how the mechanical agitation activity described in Alternative Request RV-02 relates to preconditioning.

(b)

Specify the general design, including manufacturer/vendor, for the current check valves within the scope of the request, and describe how mechanical agitation will provide sealing for the various check valve designs.

EMIB-RAI-2 Alternative Request RV-02,Section VI, Basis for Proposed Alternative, Item 2, Description of the mechanical agitation to be used, if needed, states:

Mechanical agitation is performed using a tool appropriately sized for the valve in question and for the location of the valve. The primary consideration is that the tool should not deform the valve body. The impact surface of the tool should be relatively large (greater than 1/2 diameter is preferred), and approximately flat or slightly rounded. The tool will contact the valve body surface so that it does not impact the body with an edge or sharp point. If available, a rubber coated tool may be used. In cases where there is limited access, a power-operated tool may be used provided the same precautions discussed above can be used. Agitation should be applied incrementally, starting with minimal force, and may be applied to different locations on the body, until either the disc is freed, or the plant determines agitation will not be successful. Because this activity does not lend itself to quantifiable parameters, the task is performed using the skill of the craft within the limitations discussed above. Because mechanical agitation is not a repair or replacement activity, this alternative is needed to avoid potential unnecessary emergent demands on plant equipment, resources, and personnel.

The licensee is requested to provide the following information:

(a)

Describe any experience with mechanical agitators at Sequoyah or other plants if known.

(b)

Specify the size of the actual mechanical agitators used on the 2-inch through 10-inch valves at Sequoyah if applied in the past.

(c)

Specify and describe the procedures that have been established to control the mechanical agitation activity such that the hand-operated and power-operated tools will not damage the valve seat, valve stem or pressure boundary function, etc.

(d)

Describe the weak link analysis that has been performed to verify that the mechanical agitation activity will not damage the check valves.

(e)

Explain the statement: Because mechanical agitation is not a repair or replacement activity, this alternative is needed to avoid potential unnecessary emergent demands on plant equipment, resources, and personnel.

(f)

Specify any available standard, or industry or vendor guidelines, that will be used in applying the mechanical agitators.

EMIB-RAI-3 Alternative Request RV-02,Section VI, Item 1, Review of Maintenance History of the PIVs, states, in part:

6 inclined seat swing check valves PIV leak test history has been generally satisfactorily (leakage present on 27.8%

of tests on SQN Unit 1 and 30.3% on SQN Unit 2 - no as-left failures).

10 vertical seat swing check valves PIV leak test history has improved in the last few outages and acceptable leak rates have been obtained in all cases (leakage present on 52.8% of tests on SQN Unit 1 and 75% on SQN Unit 2 - no as-left failures).

The licensee is requested to provide the following information:

(a)

Provide the evaluation of the cause of this high occurrence of leakage for the 6-inch and 10-inch check valves.

(b)

Provide the leakage rate history for 8-inch PIVs and describe the evaluation of the leakage rates.

EMIB-RAI-4 Alternative Request RV-02,Section VI, Item 3, Design of the PIV check valves, discusses the failures of PIVs at Sequoyah.

The licensee is requested to provide the following information:

(a)

Discuss if any PIVs experienced any subsequent physical damage or degradation after a mechanical agitator was applied.

(b)

Describe the evaluation of the design of each check valve to demonstrate that if a valve initially fails its leak rate test and the alternative is applied, there is no reasonable potential for disk separation or failure that might impede flow if the valve must open to perform its safety function.

EMIB-RAI-5 Alternative Request RV-02,Section IV, Reason for Request, states, in part:

Most PIVs tested at the lower pressures met the leakage rate acceptance criteria when correlated to RCS pressure. However, some PIVs have required a higher test pressure (up to nominal RCS pressure) in order to achieve acceptable leakage results. Test procedures are written to allow testing at low or higher pressures.

The licensee is requested to provide the following information:

Describe how the method to be used when implementing Alternative Request RV-02 will continue to meet ASME OM Code, paragraph ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, subparagraph ISTC-3630(b), Differential Test Pressure, and subparagraph ISTC-3630(e), Analysis of Leakage Rates, while performing PIV leakage testing at a lower pressure.

EMIB-RAI-6 Alternative Request RV-02,Section V, Proposed Alternative, in the subsection Description of the Proposed Alternative, states, in part, that PIVs that have been mechanically agitated and subsequently passed seat leakage testing, will be repaired, or replaced during the next refueling outage.

In order to support to the long-term effectiveness of Alternative Request RV-02, please discuss any plans to leak test these PIVs before they are disassembled and inspected at the next refueling outage prior to commencing with their repair or replacement to determine if agitation caused any adverse effects on valve performance.

EMIB-RAI-7 Alternative Request RV-02,Section VI, Basis for Proposed Alternative, Item 4, Description of Preventive Maintenance of the PIVs, first paragraph, states, Each unit has a scoping preventive maintenance (PM) to evaluate and identify PIVs to recommend for inspection and repair (or replace) for an upcoming refueling outage.

Please explain this statement in light of the requirement under Alternative Request RV-02 that all PIVs that have been mechanically agitated must undergo repair or replacement, and retesting, at the next refueling outage.

EMIB-RAI-8 Alternative Request RV-02,Section VI, Item 5, Description of PIV Open Exercise Testing, states in part:

While total pump design flow is instrumented and measured during every comprehensive pump test, flow through each individual injection line is instrumented and measured on an alternating basis in accordance with the check valve condition monitoring plan.

The licensee is requested to describe the ASME OM Code Appendix II check valve condition monitoring plan referenced in this item.

EMIB-RAI-9 During the pre-submittal meeting on February 16, 2022, the licensee indicated that recent operating experience has heightened TVAs awareness that mechanical agitation can lead to adequate valve sealing in addition to recent similar experience during the last Sequoyah Unit 2 outage. Please describe this experience during the last Sequoyah Unit 2 outage referenced in this meeting, and its impact on the provisions in Alternative Request RV-02.