AEP-NRC-2021-07, Supplement to Report Per Technical Specification 5.6.6, Lnoperability of Unit 1, Post Accident Monitoring, Containment Water Level

Supplement to Report Per Technical Specification 5.6.6, Lnoperability of Unit 1, Post Accident Monitoring, Containment Water Level

ML21036A125
Person / Time
Site:	Cook
Issue date:	01/28/2021
From:	Scarpello M American Electric Power, Indiana Michigan Power Co
To:	Office of Nuclear Reactor Regulation
References
AEP-NRC-2021-07
Download: ML21036A125 (3)

Text

m INDIANA Indiana Michigan Power MICHIGAN Cook Nuclear Plant POt11fER.* Ona Cook Place Bndgman, Ml 49108 A unrt ofAmencan Bectnc Power lndianaM1ch1ganPower com January 28, 2021 AEP-NRC-2021-07 10 CFR 50.4 10 CFR 50.36 Docket Nos.: 50-315 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Supplement to Report per Technical Specification 5.6.6, lnoperability of Unit 1, Post Accident Monitoring, Containment Water Level

Reference:

Letter from M. K Scarpello, Indiana Michigan Power Company, to the Nuclear Regulatory Commission, "Report per Technical Specification 5.6.6, lnoperability of Unit 1, Post Accident Monitoring, Containment Water Level," Dated November 24, 2020 (ML20332A027).

In the above Reference, Indiana Michigan Power Company (l&M), the licensee for Donald C. Cook Nuclear Plant (CNP) Unit 1, sent a report pursuant to CNP Technical Specification (TS) 3.3.3, "Post Accident Monitoring Instrumentation" and TS 5.6.6, "Post Accident Monitoring Report." The report was submitted due to Train B Lower Containment Water Level Monitor 1-NLl-320 being inoperable for greater than 30 days in accordance with TS 3.3.3, which requires entry into TS 5.6.6. This revision is being sent because the original plan to restore operability of 1-NLl-320 has changed. The current estimate for the return to operable status of Containment Water Level Monitor 1-NLl-320 is now on or about April 13, 2021. The enclosure to this letter contains a new report, in accordance with TS 3.3.3 and TS 5.6.6, for 1-NLl-320 inoperability, discussing the circumstance requiring this change.

There are no new or revised commitments in this letter. Should you have any questions, please contact me at (269) 466-2649.

~~~r Michael K. Scarpello Regulatory Affairs Director BMC/mll

U. S. Nuclear Regulatory Commission AEP-NRC-2021-07 Page 2 ,

Enclosure:

Donald C. Cook, Unit 1 Report per Technical Specification 5.6.6 lnoperability of Post-Accident Monitoring Instrument Containment Water Level, Revision 1 c: R. J. Ancona - MPSC -

EGLE - RMD/RPS J. B. Giessner - NRC Region Ill D. L. Hille - AEP Ft. Wayne, w/o enclosures NRC Resident Inspector R. M. Sistevaris - AEP Ft. Wayne, w/o enclosures S. P. Wall - NRC Washington, D.C.

A J. Williamson - AEP Ft. Wayne, w/o enclosures

Enclosure 1 to AEP-NRC-2021-07 Donald C. Cook, Unit 1 Report per Technlcal Specification 5.6.6 lnoperability of Post-Accident Monitoring Instrument Containment Water Level, Revision 1 Description of Condition On November 24, 2020, Indiana Michigan Power Company (l&M), the Licensee for Donald C. Cook Nuclear Plant (CNP) Unit 1, transmitted the Technical Specification-required report for Train B Lower Containment Water Level Monitor 1-NLl-320 being inoperable for greater than 30 days (ML20332A027). The suspected cause of inoperability is the signal processor, 1-NLl-320-SGP. The report detailed the plans to restore 1-NLl-320 to operability. Restoring 1-NLl-320 to operability required the spare electrical assembly to be sent offsite to the vendor for refurbishment. The refurbished component was expected to be installed on or about December 17, 2020. After the vendor received the spare component, they determined refurbishment was not possible. l&M elected to procure a new component, which will delay the expected restoration date of 1-NLl-320 outside of the previously expected time frame. The lead time for the new part is approximately 15 weeks. This revision updates the date that l&M expects to return 1-NLl-320 to service.

Background

The primary purpose of the Post-Accident Monitoring instrumentation is to display unit variables that provide information required by the control room operators during accident situations. Per Regulatory Guide 1.97, Revision 3, Instrumentation for Light-Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following an Accident (ML003740282), the Containment Water Level Monitor is a Type A, Category 1 variable provided for determination of adverse containment conditions. CNP Unit 1 has two containment water level channels, 1-NLl-321 and 1-NLl-320. Each channel is capable of measuring from 599' 3" elevation to 614' elevation (containment floor level to maximum flood level).

Cause of lnoperabllity The apparent cause of the failure of 1-NLl-320 is a faulty ~ignal processor, 1-NLl-320-SGP.

Preplanned Alternate Method of Monitoring The Containment Water Level Monitor consists of two redundant trains with one channel each.

Train A, 1-NLl-321, will remain operable and available while Train B, 1-NLl-320, is inoperable.

Additionally, the following instruments in containment will be used, if necessary, to monitor containment water level while 1-NLl-320 is inoperable:

1-NLl-311 - Lower Containment Sump Train A Level Indicator 1-NLA-310 - Lower Containment Sump Train B Level Alarm 1-NLl-301 - Containment Recirculation Sump Level Switch - Train A 1-NLl-300 - Containment Recirculation Sump Level Switch - Train B 1-NLl-331 - Containment Water Level Recirculation Level Switch - Train A 1-NLl-330 - Containment Water Level Recirculation Level Switch - Train B Plans and Schedule for Restoring Functlonallty l&M is procuring a new electrical assembly to return 1-NLl-320 to service. 1-NLl-320 will be returned to operable status at the next opportunity, following receipt of the new electrical assembly. As previously stated, the necessary installation can be completed online. The station estimates that 1-NLl-320 will be returned to operable status on or about April 13, 2021.