NLS2024076, Technical Specification Sections 5.6.6. - Post-Accident Monitoring Instrumentation 14-Day Report

Technical Specification Sections 5.6.6. - Post-Accident Monitoring Instrumentation 14-Day Report

ML24354A260
Person / Time
Site:	Cooper
Issue date:	12/19/2024
From:	Dewhirst L Nebraska Public Power District (NPPD)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NLS2024076
Download: ML24354A260 (1)

Text

NLS2024076 December 19, 2024 N

Nebraska Public Power District "Always there when you need us" U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

Technical Specifications Section 5.6.6 Post Accident Monitoring Instrumentation 14-Day Report Cooper Nuclear Station, Docket No. 50-298, Renewed License No. DPR-46 The purpose of this letter is to submit the Post Accident Monitoring Instrumentation Report as required by the Cooper Nuclear Station (CNS) Technical Specifications (TS) Section 5.6.6, "Post Accident Monitoring (PAM) Instrumentation Report."

The report, which is provided as an attachment to this letter, is based on the inoperability on November 11, 2024, of one required channel of the Primary Containment Gross Radiation Monitors. This condition required entry into TS Section 3.3.3.1, "Post Accident Monitoring (PAM) Instrumentation," Condition A, due to an inoperable indication channel for TS Table 3.3.3.1-1, Function 4. Condition A requires restoration of the required indication channel to an operable status within 30 days. Resolution of this issue within the 30-day requirement was not feasible due to the need for outage conditions and a primary containment entry to complete the necessary repairs. With the channel not restored to operable within 30 days, a report is required in accordance with TS Section 5.6.6.

Accordingly, the attached report outlines the preplanned alternate method of monitoring and the cause along with the plans and schedule for restoring the instrument channel to an operable status.

No formal licensee commitments are being made in this letter. Should you have any questions concerning this matter, please contact me at (402) 825-5416.

Lin* a Dewhirst Regulatory Affairs & Compliance Manager

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Attachment:

Post Accident Monitoring Instrumentation 14-Day Report COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 http://www.nppd.com

NLS2024076 Page 2 of2 cc:

Regional Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Plant Licensing Branch IV Senior Resident Inspector w/attachment USNRC-CNS NPG Distribution w/attachment CNS Records w/attachment

NLS2024076 Attachment Page 1 of2 Post Accident Monitoring Instrumentation 14-Day Report Preplanned Alternate Method of Monitoring The Cooper Nuclear Station (CNS) Primary Containment Gross Radiation Monitors (also known as Containment High Range Monitors or Drywell Radiation Monitors in CNS procedures) are provided to monitor and assess the potential for fission product barrier (Fuel Clad, Reactor Coolant System, Primary Containment) degradation in support of the site emergency plan procedures. Alternate methods contained in existing CNS procedures for determining fission product barrier degradation are:

Redundant channel of the Primary Containment Gross Radiation Monitors. This redundant radiation monitor indication is located within the CNS Main Control Room (MCR) and the associated radiation detector is inside of primary containment, approximately 180 degrees radially from the inoperable radiation detector.

Reactor Pressure Vessel Water Level Indications (Indication - CNS MCR).

Reactor Water Sample Analysis.

Main Steam Line Radiation Monitors (Indication - CNS MCR).

Off-Gas (Steam Jet Air Ejector (SJAE)) Radiation Monitors (Indication - CNS MCR).

Drywell Pressure Indications (Indication - CNS MCR).

Drywell Temperature Indications (Indication - CNS MCR).

Primary Containment H2 and 02 Concentration Indications (Indication - CNS MCR).

These alternate methods provide an acceptable preplanned method for determining fission product barrier degradation in support of operational decision making and classification. The Primary Containment High Range Radiation Monitor indication anomaly has been entered into the Corrective Action Program for final resolution.

Cause of the Inoperability The cause of the intermittent erratic radiation indication from the Primary Containment Gross Radiation Monitor is electronic noise susceptibility of the instrument loop signal path.

Restoration activities to date have replaced the accessible components in the instrument loop that are located outside of primary containment, including the readout module in the CNS MCR and the accessible signal cable connectors. Troubleshooting to date has concluded the noise source and signal degradation is likely located in the part of the instrument loop that is located inside primary containment. This part of the instrument loop contains the radiation detector, signal cable (including electrical connectors), and the high-voltage containment electrical penetration that provides the signal path out of primary containment.

The Primary Containment Gross Radiation Monitor's automated Electronic Check Source feature has confirmed that detector and signal path are intact and reading local radiation.

However, intermittent noise is causing the electronic signal to spike, resulting in spurious high radiation alarms. The Primary Containment Gross Radiation Monitor's instrument loop

NLS2024076 Attachment Page 2 of2 components that are located inside primary containment are not accessible during plant operation.

Plans and Schedule for Returning Function to Operable Status Repair of the instrument loop components located inside of primary containment requires a plant outage with drywell entry. The Primary Containment Gross Radiation Monitor instrument loop will be repaired as opportunity allows, and no later than the next scheduled refueling outage.