ML20160A023

SR 2020-001-00 for Browns Ferry Nuclear Plant (Bfn),Inoperable Oscillating Power Range Monitor (OPRM) Instrumentation

ML20160A023
Person / Time
Site:	Browns Ferry
Issue date:	06/04/2020
From:	Bono S Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SR 2020-001-00
Download: ML20160A023 (3)

Text

[I!fil Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 June 4, 2020 10 CFR 50.4 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 3 Renewed Facility Operating License No. DPR-68 NRC Docket No. 50-296

Subject:

Browns Ferry Nuclear Plant (BFN) - Special Report 296/2020-001 for Inoperable Oscillating Power Range Monitor (OPRM) Instrumentation In accordance with Technical Specification (TS) 5.6.7, OPRM Report, this letter provides notification of inoperable OPRM instrumentation. Due to the inoperability of BFN Unit 3 OPRM instrumentation channels during the implementation of the Maximum Extended Load Line Limit Analysis Plus (MELLLA+) License Amendment, TS 3.3.1.1, Reactor Protection System (RPS)

Instrumentation, Condition I was entered and associated Required Action I.3 of TS 3.3.1.1 was taken to immediately initiate action to submit an OPRM report in accordance with TS 5.6.7.

BACKGROUND INFORMATION:

On March 10, 2020, the MELLLA+ License Amendment was implemented for BFN Unit 3. At that time BFN Unit 3 was in Mode 5, Refueling. One of the changes approved by the NRC in the MELLLA+ License Amendment was the use of the Detect and Suppress Solution -

Confirmation Density (DSS-CD) thermal-hydraulic stability solution, instead of the previous approved Option III thermal-hydraulic stability solution. At the time of implementation, the BFN Unit 3 OPRMs were configured for compliance with DSS-CD thermal-hydraulic stability solution. However, completion of certain MELLLA+ testing and placing the confirmation density algorithm of the DSS-CD in service are required for the OPRMs to be considered Operable.

These activities were not planned to be completed until after the OPRM Condition of Applicability (i.e., > 18% Rated Thermal Power (RTP)) was reached following startup from the BFN Unit 3 Spring 2020 refueling outage. As a result, all channels of the OPRM Upscale Function were inoperable on March 26, 2020, when BFN Unit 3 reached 18% RTP following startup from the refueling outage. The applicable Required Actions of TS 3.3.1.1 were taken prior to BFN Unit 3 reaching 18% RTP. Subsequently, on April 1, 2020, power on BFN Unit 3 was reduced below 18% RTP in preparation for a forced outage. On April 6, 2020, during

U.S. Nuclear Regulatory Commission Page 2 June 4, 2020 startup from the forced outage, the OPRM Condition of Applicability was again reached. At that time, all applicable Required Actions of TS 3.3.1.1 for inoperable OPRM channels were satisfied.

TS Table 3.3.1.1-1, Function 2.f, requires three of the four OPRM Upscale channels to be Operable. With one or more required OPRM Upscale channels inoperable, TS 3.3.1.1 Required Action A.1 requires the inoperable channels to be placed in trip within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. With all four of the OPRM Upscale channels inoperable, the associated RPS trip capability is not maintained and TS 3.3.1.1 Required Action C.1 requires restoration of RPS trip capability to be restored within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. If a Required Action and associated Completion Time is not met, TS 3.3.1.1 Required Action D.1 requires entry into the Condition referenced in Table 3.3.1.1-1 for the channel. For channels associated with Function 2.f, Table 3.3.1.1-1 references Condition I.

TS 3.3.1.1 Condition I includes Required Actions to immediately initiate action to implement Manual Backup Stability Protection Regions (Required Action I.1), within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> implement the Automated Backup Stability Protection Scram Region (Required Action I.2), and immediately initate action to submit an OPRM report in accordance with TS 5.6.7 (Required Action I.3).

Action was initiated, on March 10, 2020, to submit the OPRM report in accordance with TS 5.6.7. TS 5.6.7 requires, when an OPRM report is required by Condition I of TS 3.3.1.1, that the report be submitted to NRC within the following 90 days. The OPRM report is required to outline the preplanned means to provide backup stability protection, the cause of the inoperability and the plans and schedule for restoring the required instrumentation channels to Operable status.

CAUSE OF THE INOPERABILITY:

The cause of the inoperability of the OPRM Upscale channels was a preplanned evolution to implement the BFN Unit 3 MELLLA+ License Amendment with the unit in Mode 1 above 18% RTP (i.e., the condition of Applicability for the OPRM Upscale channels) following startup from the BFN Unit 3 Spring 2020 refueling outage. On March 10, 2020, when the BFN Unit 3 MELLLA+ License Amendment was implemented, the OPRM Upscale channels were configured for compliance with the DSS-CD thermal-hydraulic stability solution. However, certain MELLLA+ testing had not been completed and the confirmation density algorithm of the DSS-CD had not been placed in service. These activities were required to be completed for the OPRM Upscale channels to be considered Operable. Therefore, upon implementing the BFN Unit 3 MELLLA+ License Amendment and when BFN Unit 3 first reached 18% RTP, the OPRM Upscale channels were inoperable.

PREPLANNED MEANS OF BACKUP STABILITY PROTECTION:

Upon declaring the OPRM Upscale channels inoperable and prior to entering the OPRM Condition of Applicability, the following preplanned means of backup stability protection were implemented.

x Operations personnel immediately initiated action to implement the Manual Backup Stability Protection Regions in accordance with TS 3.3.1.1 Required Action I.1. Operations personnel were required to immediately verify unit operation was outside of Manual Backup

U.S. Nuclear Regulatory Commission Page 3 June 4, 2020 Stability Protection Regions, i.e., Region 1 (Scram) and Region 2 (Controlled Entry) of the power/flow map. In addition, Operations personnel were required by procedures to monitor for thermal-hydraulic oscillations if unit operation was within 10% of the rated core flow or power of Region 2 of the power/flow map. Operations personnel were also required by procedures to re-perform the verifications each time core flow was lowered by 10% or reactor power was raised by 5%, when flow was below 75% of rated core flow and power was above 18% rated thermal power.

x In accordance with TS 3.3.1.1 Required Action I.2, within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, the Automated Backup Stability Protection Scram Region was implemented. To implement the Automated Backup Stability Protection Scram Region, Maintenance personnel implemented the modified Average Power Range Monitor (APRM) Flow Biased Simulated Thermal Power - High Scram setpoints specified in the Core Operating Limits Report for the Automated Backup Stability Protection Scram Region.

PLANS AND SCHEDULE FOR RESTORING THE REQUIRED INSTRUMENTATION CHANNNELS:

On April 24, 2020, upon completion of certain MELLLA+ testing and placing the confirmation density algorithm of the DSS-CD in service, the OPRM Upscale channels were declared Operable.

There are no new regulatory commitments associated with this submittal. If there are any questions or if additional information is needed, please contact J. L. Paul, Nuclear Site Licensing Manager, at (256) 729-2636.

Respectfully, S. M S M. Bono o Site Vice President cc:

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant