ML20231A717

Request for Additional Information (e-mail Dated 8/18/2020) License Amendment Request to Revise TS Table 3.3-11 Accident Monitoring Instrumentation

ML20231A717
Person / Time
Site:	Millstone
Issue date:	08/18/2020
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Sinha S Dominion Energy Nuclear Connecticut
Guzman R
References
EPID L-2020-LLA-0039
Download: ML20231A717 (5)

Text

From: Guzman, Richard To: Shayan.Sinha@dominionenergy.com

Subject:

Millstone Power Station, Unit No. 2 - REQUEST FOR ADDITIONAL INFORMATION re: LAR to revise TS Table 3.3-11, Accident Monitoring Instrumentation [EPID: L-2020-LLA-0039]

Date: Tuesday, August 18, 2020 9:56:03 AM

Shayan, On August 3, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff sent Dominion Energy Nuclear Connecticut, Inc. (DENC) the subject Request for Additional Information (RAI) as a draft (via e-mail shown below).This RAI relates to the license amendment request submitted by DENC dated March 3, 2020 (ADAMS Accession No. ML20065K976),

proposing to revise Action 3 in Technical Specification Table 3.3-11, Accident Monitoring Instrumentation, for monitoring PORV and PSV valve position when any of the three valve position monitoring indications (i.e., Instruments 4, 5 and 6) become inoperable.

On August 13, 2020, the NRC staff conducted a conference call with the licensee staff to clarify the request. Following the discussion, you indicated that DENC will provide a response to this RAI within 30 days from the issuance of the RAI; therefore, the NRC staff expects DENCs formal response by September 18, 2020. Updated below is the official (final) RAI. A publicly available version of this e-mail and RAI will be placed in the NRCs ADAMS system. Please contact me should you have any questions in regard to this request.

Sincerely, Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov From: Guzman, Richard <Richard.Guzman@nrc.gov>

Sent: Monday, August 3, 2020 11:17 AM To: Shayan Sinha (Services - 6) <Shayan.Sinha@dominionenergy.com>

Subject:

[EXTERNAL] Millstone Unit 2 - DRAFT Request for Additional Information - LAR to revise TS Table 3.3-11, Accident Monitoring Instrumentation [EPID: L-2020-LLA-0039]

Shayan, By letter dated March 3, 2020 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML20065K976), Dominion Energy Nuclear Connecticut, Inc. (DENC, the licensee) submitted a license amendment request (LAR) for the Millstone Power Station, Unit No. 2 (MPS2). The proposed license amendment would revise Action 3 in Technical Specification Table 3.3-11, Accident Monitoring Instrumentation, for monitoring PORV and PSV valve position when any of the three valve position monitoring indications (i.e., Instruments 4, 5 and 6) become inoperable.

The NRC staff has reviewed the LAR and determined that additional information is needed to complete its review, as described in the request for additional information (RAI) shown below. This RAI is identified as DRAFT at this time to confirm your understanding of the information needed by the NRC staff to complete

its evaluation. Please let me know your groups availability for a clarification call to be held within the next two weeks with the technical staff. I intend to send out the questions below as official upon completion of our clarification call by 8/14, if possible.

Thanks, Rich Guzman Sr. PM, Division Operator Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov

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REQUEST FOR ADDITIONAL INFORMATION LAR TO REVISE TS TABLE 3.3-11, ACCIDENT MONITORING INSTRUMENTATION MILLSTONE POWER STATION, UNIT NO. 3 DOCKET NO. 50-336 EPID L-2020-LLA-0039 By letter dated March 3, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20065K976), Dominion Energy Nuclear Connecticut, Inc.

(DENC, the licensee) submitted a license amendment request (LAR) for the Millstone Power Station, Unit No. 2 (MPS2). The proposed license amendment would revise Action 3 in Technical Specification (TS) Table 3.3-11, Accident Monitoring Instrumentation, for monitoring PORV and PSV valve position when any of the three valve position monitoring indications (i.e., Instruments 4, 5 and 6) become inoperable. The NRC staff has reviewed the LAR and determined that additional information is necessary to complete its review, as described in the request for additional information (RAI) shown below.

Background

When valve position indications for Instrument 4 power-operated relief valves (PORVs),

Instrument 5 PORV block valves, or Instrument 6 pressurizer safety valves (PSVs) are inoperable, MPS2 TS Table 3.3-11, Action 3 currently requires control room operators to obtain quench tank temperature, level and pressure information, and monitor discharge pipe temperature once per shift to determine valve position. Action 3 currently requires that all of the identified parameters must be monitored once per shift. The licensee requested to revise Action 3 in Table 3.3-11 to address what the licensee considers as unnecessary restrictions for monitoring valve position when any of the three valve position monitoring indications (i.e., Instruments 4, 5 and 6) become inoperable. The licensee proposes the following INSERT to Action 3:

With the number of OPERABLE accident monitoring instrumentation channels less than the required Minimum Channels OPERABLE in Table 3.3-11 and one or more of the above mentioned quench tank parameters or discharge pipe temperatures unavailable, either restore the inoperable accident monitoring instrumentation channel to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, or prepare and submit a Special

Report to the Commission pursuant to Specification 6.9.2 within the next 10 days outlining the cause of the malfunction, the plans for restoring the accident monitoring instrumentation channel to OPERABLE status, and any alternate methods in effect for determining if there is a loss of coolant through an inadvertently open valve during the interim.

Regulatory Basis The regulation at 10 CFR 50, Appendix A, General Design Criteria (GDC) 13, Instrumentation and control, requires, in part, that instrumentation shall be provided to monitor variables and systems over their anticipated ranges for normal operation, for anticipated operational occurrences, and for accident conditions as appropriate to assure adequate safety.

Generic Letter 80-90 incorporated into one document (NUREG-0737) all TMI-related items approved for implementation by the Commission. Item II.D.3 of NUREG-0737 requires that reactor coolant system relief and safety valves shall be provided with a positive indication in the control room derived from a reliable valve-position detection device or a reliable indication of flow in the discharge pipe.

Regulatory Guide 1.97, Revision 2, Table 2 specifies that the purpose for monitoring the variable "Primary System Safety Relief Valve Positions (including PORV and code valves) or Flow Through or Pressure in Relief Valve Lines" is to provide operational status and to monitor for loss of coolant.

Request for Additional Information The application does not provide sufficient details for the staff to adequately assess how alternate methods as described can be sufficient to serve as a reliable method to provide position indication in the control room, derived from a reliable valve-position detection device or a reliable indication of flow in the discharge pipe. Based on the proposed wording, it appears that any combination, including all, of the direct parameters could be unavailable and the plant could continue operating indefinitely in this condition. The application provides general examples of alternative, indirect means to diagnose whether there is loss of coolant through a PORV or PSV, so that restorative or mitigative actions can be taken. However, the examples do not appear to be actual alternative means that the licensee is committing to follow using developed procedures accounting for the possible combinations of available direct or indirect parameters. In addition, a technical basis is needed to demonstrate that potential alternative methods and operator diagnostics will be reliable in promptly identifying loss of coolant, consistent with the current actions in Action

3. The following information is needed to verify compliance with the requirements of 10 CFR 50 Appendix A, GDC 13 and NUREG-0737 and conformance with RG 1.97.

RAI 1

The proposed TS Action 3 appears to allow continued operation for an unspecified interim period with any combination, including all, of the direct parameters being unavailable, with a TS 6.9.2 Special Report submitted to NRC to describe the alternate method in effect for determining if there is a loss of coolant through an inadvertently open valve. Please confirm if the intent of the TS is to continue plant operations in all possible combinations indefinitely (e.g., for the remainder of the operating cycle and beyond), including potential conditions in which all direct parameters are unavailable. Discuss how the requirements are met in these potential conditions, specifically those in NUREG-0737, Position II.D.3, to

provide positive indication in the control room derived from a reliable valve-position detection device or a reliable indication of flow in the discharge pipe.

RAI 2

The proposed change could allow MPS2 to enter revised Action 3 without any quench tank parameters and only discharge pipe temperature measurements as the only remaining direct parameter. Justify that this potential condition (i.e., the availability of only the discharge pipe temperature indication) would provide a reliable indication of valve position or flow in the discharge pipe. In the response, please address the following:

• The normal operating temperature ranges for the discharge pipe temperatures compared to anticipated temperatures with allowable amounts of seat leakage and with an open valve.

• Impact of containment ambient temperature on discharge pipe temperatures when containment is at its hottest (i.e. during the summer at 100% power) and the ability to timely detect an open valve.

• How operators distinguish between temperature increases in the discharge piping due to allowable seat leakage and other factors versus an open valve.

• Existing operator actions that are taken when the discharge pipe temperature for one of the valves is rising, prior to, and when reaching, the alarm setpoint. What changes, if any, are there based on the proposed LAR?

RAI 3

The LAR (Attachment 1, bottom of Page 6 of 11) states, Since multiple, independent instruments are available to the operator to provide indication of an inadvertently opened PORV or PSV, loss of one or more of these instruments would not preclude the operator from correctly diagnosing the condition. Discuss what is meant by independent as used here to describe the direct parameters. For example, are there any shared power supplies, annunciator equipment, or other single point failure vulnerabilities associated with the PORV, PORV block and PSV position indication equipment and any of the direct parameters?

RAI 4

The proposed Action 3 would allow the reduction in operability requirements for direct parameter measurements, and thus, a reduction in defense-in-depth in identifying an open valve when the primary accident monitoring position indication is inoperable. The NRC staff is evaluating whether there will still be reasonable assurance in the positive indication in the control room of a reliable indication of flow in the discharge pipe. Provide a discussion regarding the reliability in determining PORV or PSV status when a reduced number of direct parameter instruments is available (i.e., loss of any quench tank temperature, level, and pressure, and discharge pipe temperatures) and for a total loss of all direct parameters, as allowed for in the proposed Action 3. Describe the surveillance or maintenance that is normally performed for these direct parameter instruments. Describe the proposed actions that will be taken to restore any of the direct parameters, once the proposed TS revision goes into effect.

RAI 5

While in proposed Action 3, clarify if there are procedures to address the various combinations of available direct and indirect parameters for verifying positive indication in the control room derived from a reliable valve-position detection device or a reliable indication of flow in the discharge pipe. With the current and proposed Action 3, readings

are taken once per shift of the direct parameters. Is there a continued or modified requirement to obtain these readings when one or more of the direct parameters are unavailable?