NLS2022042, 10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2) Summary Report

10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2) Summary Report

ML22280A156
Person / Time
Site:	Cooper
Issue date:	10/07/2022
From:	Dewhirst L Nebraska Public Power District (NPPD)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NLS2022042
Download: ML22280A156 (5)

Text

H Nebraska Public Power District "Alw11ys ti.ere when you need 1ts" 50.59(d)(2) 72.48(d)(2)

NLS2022042 October 7, 2022 U.S. Nuclear Regulatory Commission Attention : Document Control Desk Washington, D.C. 20555-0001

Subject:

10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2) Summary Report Cooper Nuclear Station, Docket No. 50-298, License No. DPR-46

Dear Sir or Madam:

The purpose of this letter is for the Nebraska Public Power District to provide the summary report of evaluations that have been performed for Cooper Nuclear Station, in accordance with the requirements of 10 CFR 50.59(d)(2) and IO CFR 72.48(d)(2). This report covers the time period from August 1, 2020, to July 31, 2022. Summaries of applicable facility changes are discussed in the Attachment. There were no 72.48 evaluations performed during the specified time period.

There are no commitments contained in this letter.

Should you have any questions concerning this matter, please contact me at (402) 825-5416.

Linda Dewhir t Regulatory Affairs and Compliance Manager

/mu

Attachment:

Facility Changes COOPER NUCLEAR STATION 72676 648A Ave/ P.O. Box 98 / Brownville, NE 68321 http://www.nppd.com

NLS2022042 Page 2 of2 cc: Regional Administrator w/ attachment USNRC - Region IV Senior Resident Inspector w/ attachment USNRC-CNS Cooper Project Manager w/ attachment USNRC - NRR Plant Licensing Branch IV NPG Distribution w/ attachment CNS Records w/ attachment

NLS2022042 Attachment Page 1 of 3 Attachment Facility Changes The following is a summary of the 50.59 evaluation that was prepared to support a facility change implemented at Cooper Nuclear Station (CNS) during the time period from August 1, 2020 to July 31, 2022.

Temporary Configuration Change (TCC) 5395350 (Evaluation 2021-1, Revision 1)

Title:

MS-AOV-790AV Packing Leak Repair

Description:

TCC 5395350 repaired a packing leak on MS-AOV-790AV, Residual Heat Removal (RHR) Heat Exchanger A Steam Dripleg Drain Trap 17 Bypass Valve, by increasing the torque applied to the packing gland nuts beyond the limit previously authorized, in order to increase the consolidation of the valve packing. Consolidation of the valve packing forces the packing to extrude into the openings and crevices to seal the steam path and stop the leak.

MS-AOV-790AV is a normally closed bypass valve for the Main Steam Trap Station 17 associated with the original steam supply piping for the RHR Heat Exchanger A dripleg drain. This piping branches off of the steam supply piping for the High Pressure Coolant Injection (HPCI) steam turbine. MS-AOV-790AV opens upon a high-water level within the dripleg drain piping to bypass the steam trap and drain the moisture to the Main Condenser or the Feedwater Heaters.

MS-AOV-790AV performs two design functions within the steam supply piping. The first function is that the valve provides a pressure boundary to ensure that the steam supply is available to support the HPCI system. This function has been determined to not be affected by the activity. The second function (non-essential) that this valve provides is a flow path, upon receipt of a high-waterlevel signal from Main Steam Level Switch MS-LS-101, Low Point Moisture Trap Blowdown Interlock, to drain the excess moisture from the piping. This function is a backup method to support that the piping configuration is in agreement with the assumptions of the piping analysis (piping analyses do not account for moisture accumulating within the piping when a seismic event occurs). This function is primarily performed by the steam trap within the drain piping. Due to the increased packing friction resulting from the additional consolidation of the packing, it is assumed that movement of MS-AOV-790AV will not occur due to the limited capabilities of the valve actuator.

NLS2022042 Attachment Page 2 of3 As such, an alternate method was instituted to drain the moisture from this piping should MS-LS-101 alarm and not clear. This alternate method included actions to manipulate manual valves within the system piping to create a drain path when a high-water level alarm from level switch MS-LS-101 is received and will not clear. This alternate method was evaluated as a temporary manual action that is replacing an automatic action. The temporary manual method was instituted to support the initial assumptions of the piping analyses. The alarm response procedure was revised by this activity to provide the requirement to manually drain the piping within a 14-day time frame.

This TCC also established limitations for this activity. The manual draining of the piping and the installed steam trap cannot assure that the piping will be free of moisture accumulation during plant start-ups or the re-admittance of steam to this section of piping. As such, if the steam supply to this section of piping were to be impacted, then the functionality ofMS-AOV-790AV has to be restored or the alarm cleared prior to returning the applicable systems to service.

10CFR The evaluation concluded that the manual method of draining moisture from the 50.59 applicable section of the Main Steam piping is adequate and will provide an Evaluation: acceptable backup method of supporting the assumed starting conditions of the subject piping analysis.

The failure of the HPCI system to function is not an initiator in the station safety analyses for design basis accidents and operational transients. Additionally, the pipe stress analysis for the HPCI steam supply piping and the means of removing excess moisture from the piping are not inputs to the frequency of occurrence of accidents.

MS-AOV-790AV and its associated piping support the pressure boundary function of the steam supply to the HPCI turbine. This piping has been analyzed to ensure that it meets the Seismic Class IS requirements. The tightening of the valve packing gland nuts does not impact any of these requirements. However, disabling MS-AOV-790AV to move prevents the valve from performing its secondary function of draining moisture from the piping upon a failure of the Main Steam trap or an accumulation of moisture that exceeds the capacity of the Main Steam trap. Procedure guidance was implemented that directs a manual alternative action to drain the piping upon receipt of a high-water level alarm from level switch, MS-LS-101, within 14 days. Review of piping analyses determined this will not impact the ability of the piping to perform its intended function as the piping stresses will remain less than Code allowable limits.

Implementation of the alternative means for draining moisture requires an Operator to be in the area for monitoring and isolating the drain path once the accumulated moisture is removed. The location of the valves required to be manipulated for this alternative action are in a readily accessible, non-harsh

NLS2022042 Attachment Page 3 of3 area, and consists of routine Operator actions to complete. Mal operation or mispositioning of a valve during the draining would be readily apparent and subsequent actions are in place (valve closing) to isolate the drain path.

The alternate method to drain the piping of moisture supports the piping analyses initial assumptions, it does not introduce any new system level malfunctions, no new system level failure modes are created, and does not necessitate a revision or replacement of any currently used evaluation methodology.

It is concluded that implementation of this change does not require a Technical Specification change, does not require a License Amendment, and therefore may proceed without NRC approval.