05000341/LER-2021-001, Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis

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Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis
ML21182A291
Person / Time
Site: Fermi DTE Energy icon.png
Issue date: 07/01/2021
From: Peter Dietrich
DTE Electric Company
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC-21-0035 LER 2021-001-00
Download: ML21182A291 (9)


LER-2021-001, Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition

10 CFR 50.73(a)(2)(v), Loss of Safety Function

10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3412021001R00 - NRC Website

text

Peter Dietrich Senior Vice President and Chief Nuclear Officer DTE Electric Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.4153 Fax: 734.586.1431 Email: peter.dietrich@dteenergy.com 10 CFR 50.73 July 1, 2021 NRC-21-0035 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Fermi 2 Power Plant NRC Docket No. 50-341 NRC License No. NPF-43

Subject:

Licensee Event Report (LER) No. 2021-001 Pursuant to 10 CFR 50.73(a)(2)(i)(B), 10 CFR 50.73(a)(2)(ii)(B), 10 CFR 50.73(a)(2)(v), 10 CFR 50.73(a)(2)(vii), and 10 CFR 50.72(a)(2)(ix)(A), DTE Electric Company (DTE) is submitting LER No. 2021-001, Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis.

No new commitments are being made in this submittal.

Should you have any questions or require additional information, please contact Mr. Ertman L.

Bennett III, Manager - Nuclear Licensing, at (734) 586-4273.

Sincerely, Peter Dietrich Senior Vice President and Chief Nuclear Officer Enclosure: Licensee Event Report No. 2021-001, Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis cc:

NRC Project Manager NRC Resident Office Regional Administrator, Region III

Enclosure to NRC-21-0035 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2021-001 Unrecognized Impact of Opening of Barrier Doors on High Energy Line Break Analysis

Abstract

The Fermi 2 Reactor Building Steam Tunnel (RBST) has a normally closed door which is credited as a hazard barrier for certain high energy line break (HELB) scenarios. On May 3, 2021, while Fermi 2 was operating at 100% reactor power in MODE 1, it was determined that the RBST door had been open on seven occasions within the past three years for longer than required for ingress/egress and that this condition was not bounded by site analyses. If a postulated HELB had occurred while the door was open during those seven occasions, equipment outside the RBST may have been adversely impacted by the post-HELB conditions. It was determined that the conditions were reportable as a condition prohibited by Technical Specifications (TS), loss of safety functions, an unanalyzed condition, a common cause inoperability, and a single cause preventing safety functions in different systems. Due to the door being open for only a short time in each case, a bounding risk evaluation determined that the safety significance was very low. There were no radiological releases associated with this event.

The cause of this event was the failure of Operations personnel to properly follow site procedures which prohibited the opening of the door (other than during ingress/egress) without prior evaluation by site engineering. Immediate corrective action was taken to restrict opening of the RBST door to ingress/egress only. Additional longer-term corrective actions are planned to perform new HELB analyses that establish specific conditions under which the RBST door may remain open.

below, while written specifically for the more recent (i.e., April 2021) occurrences, is also generally applicable to these older occurrences.

Indications of a steam leak in the RBST led to the decision for personnel to access the RBST and investigate the source of the leak and perform repairs if possible. Since door R1-11 opens into the room, a steam leak in the room could pressurize the room and make it difficult to open from the inside. For this reason, station personnel made the decision to leave the R1-11 door open while any personnel were inside the room. Door R1-11 was not disabled from closing but remained open to facilitate personnel safety to allow for prompt egress if needed.

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3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.

The reason for leaving the RBST door open in April of 2021 was as a safety precaution while personnel were inside the RBST to investigate a potential steam leak. The steam leak was identified and repaired during the week of May 17, 2021. The repairs were performed while the plant was shut down, which eliminated concerns regarding the RBST door being open. Repair of the steam leak has eliminated the need for entry to the RBST in the foreseeable future. This will allow the door to remain in its closed position, consistent with analysis assumptions.

In addition, further investigation is being performed under the Fermi 2 Corrective Action Program (CAP) to determine if other doors (i.e., other than R1-11) have also been improperly controlled during maintenance activities. The investigation is ongoing.

PREVIOUS OCCURRENCES

There have been no other previous reportable events concerning the RBST door. However, this report did include documentation of the previous occurrences in the past three years. As described above, an investigation is ongoing under the Fermi 2 CAP to determine if there may have been previous occurrences of a similar nature associated with other similar doors.

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