05000250/LER-2021-001, Automatic Reactor Trip Due to Reactor Trip Breaker Cell Switch Malfunction
| ML21119A005 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 04/29/2021 |
| From: | Pearce M Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2021-084 LER 2021-001-00 | |
| Download: ML21119A005 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(B)(6) |
| 2502021001R00 - NRC Website | |
text
U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 RE: Turkey Point Unit 3 Docket No. 50-250 Repo1iable Event: 2021-001-00 Date of Event: March 1, 2021 10 CPR 50.73 L-2021-084 April 29, 2021 Title: Automatic Reactor Trip due to Reactor Trip Breaker Cell Switch Malfunction The attached Licensee Event Rep01i 05000250/2021-001-00 is submitted pursuant to 10 CPR 50.73 (a)(2)(iv)(A), due to automatic actuation of the Unit 3 Reactor Protection System and Auxiliary Feedwater System.
If there are any questions, please call Mr. Robe1i Hess at 305-246-4112 or e-mail Robe1i.Hess@fpl.com.
Sincerely, Michael Pearce Site Vice President - Turkey Point Nuclear Plant Florida Power & Light Company Attachments: USNRC Forms 366 and 366A, current revision cc: USNRC Senior Resident Inspector, Turkey Point Plant USNRC Regional Administrator, Region II Florida Power & Light Company 9760 SW 344th St., Homestead, FL 33035
Abstract
Turkey Point Unit 3 250 3
Automatic Reactor Trip due to Reactor Trip Breaker Cell Switch Malfunction 03 01 2021 2021 001 00 04 29 21 1
100
David Stoia - Licensing Engineer (305) 246-6538 B
AA BKR W120 Y
On 3/1/21 at 11:08 hours, Turkey Point Unit 3 experienced an unplanned reactor trip from 100% power. Restoration from a routine test of the Reactor Protection System (RPS) was in progress when the reactor trip occurred. As expected for the conditions, the Auxiliary Feedwater System (AFW) automatically initiated in response to the reactor trip to maintain Steam Generator levels in normal bands. All equipment required for the immediate reactor trip response functioned normally.
A malfunction of the B-train Reactor Trip Breaker cubicle cell switch during the RPS test restoration caused the reactor trip. The breaker and cell switch have since been replaced and Unit 3 returned to normal power operation.
This event is reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A) for initiation of the Reactor Protection [10 CFR 50.73(a)(2)(iv)(B)
(1)] and Auxiliary Feedwater [10 CFR 50.73(a)(2)(iv)(B)(6)] systems.Page of 05000-
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
SAFETY SIGNIFICANCE
The safety significance of this event is low. All equipment required for immediate response to the automatic reactor trip functioned as designed. One SDTC valve was slow to close, causing automatic isolation letdown and prompting the Reactor Operator to take manual control of pressurizer level. This equipment condition did not complicate the response or lessen the margin of safety that was maintained throughout the event.
CORRECTIVE ACTIONS
- - The Unit 3 RTB was replaced.
- - The Unit 3 RTB cell switches were replaced.
- - The Unit 3 RTA, BYA, and BYB breaker cubicles and cell switches were inspected, cleaned, and tested for proper operation.
- - A modification to detect for a standing trip signal from cell switch contacts was installed on Unit 3 RTA, RTB, BYA, and BYB.
- - Work orders for Unit 4 RTA, RTB, BYA, and BYB cell switch inspection will be originated and scheduled for next Unit 4 outage.
- - A modification to detect for a standing trip signal from cell switch contacts for Unit 4 RTA, RTB, BYA, and BYB will be developed and scheduled for implementation during the next Unit 4 refueling outage.
- - A revision will be submitted to procedure 0-PME-049.01, Reactor Trip and Bypass Breaker Inspection and Maintenance, to require cleaning and lubrication of cell switch contacts.
- - SV-3-1440, modulating solenoid for CV-3-2830, was replaced.
- - AR 2385529 will prescribe additional actions to address the contributing causes and condition extent.
ADDITIONAL INFORMATION
EIIS Codes are shown in the format [IEEE system identifier, component function identifier, second component function identifier (if appropriate)].
SIMILAR EVENTS
A review of reactor trip events over the previous 5 years was performed to identify similar events or patterns. No reactor trips have occurred due to a malfunction of a RTB. No history of cell switch failure was identified.
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