05000483/LER-2022-001, Reactor Trip During Reactor Trip Breaker Surveillance Testing
| ML22066B310 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/07/2022 |
| From: | Bianco F Ameren Missouri, Union Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-06713 LER 2022-001-00 | |
| Download: ML22066B310 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 4832022001R00 - NRC Website | |
text
Amerefl MISSOURI March 7, 2022 Callaway Plant u.s. Nuclear Regulatory Commission AUn: Document Control Desk Washington, DC 20555-000 1 Ladies and Gentlemen:
ULNRC-067 13 10 CFR 50.73 DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
RENEWED FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2022-001-00 REACTOR TRIP DURING REACTOR TRIP BREAKER SURVEILLANCE TESTING The enclosed licensee event report (LER) is submitted in accordance with 1 OCFR5O.73(a)(2)(iv)(A) to report a reactor protection system actuation (reactor trip) and auxiliary feedwater actuation.
This letter does not contain new commitments.
Enclosure LER 2022-001-00 Fred Senior Director, Nuclear Operations
$315 County Road 459 Steedman, MO 65077 AmerenMissouri.com
ULNRC-067 13 March 7, 2022 Page 2 of 3 cc:
Mr. Scoff A. Morris Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U. S. Nuclear Regulatory Commission
$201 NRC Road Steedman, MO 65077 Mr. M. Chawla Project Manager, Callaway Plant Office ofNuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop O8B1A Washington, DC 20555-0001
ULNRC-067 13 March 7, 2022 Page3 of 3 Index and send hardcopy to QA file A160.0761 Hardcopy:
Certrec Corporation 6500 West freeway, Suite 400 Fort Worth, TX 76116 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)
Electronic distribution for the following can be made via LER ULNRC Distribution:
F. M. Diya B. L. Cox F. J. Bianco S. P. Banker M. A. McLacfflan K. A. Mills T. A. Wift R. C. Wink T. B. Elwood Corporate Oversight NSRB Secretary Performance Improvement Coordinator Resident Inspectors (NRC)
STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)
Ms. Kathleen McNelis (Public Service Commission)
Ms. Claire Eubanks (Public Service Commission)
Abstract
Mth the plant at full power on January 7, 2022, an undetected relay failure Caused the solid-state reactor protection system (SSPS) to actuate during restoration from a Reactor Trip Breaker B Trip Actuating Device Operational Test, thus resulting n an unplanned reactor trip.
The reactor trip was reported per Event Notification 55698 in accordance with 10 CFR 50.72(b)(2)(iv)(B) and 50.72(b)(3)(iv)(A).
The cause of the reactor trip was that procedure OSP-SB-0001 B, Reactor Trip Breaker B Trip Actuating Device Dperational Test, did not include adequate instructions for verifying the absence of a B train General Warning trip signal prior to operating the A train Multiplexer Test Switch during test restoration. This was due to inadequate guidance for development of the procedure.
Dorrective Actions include revising Operations surveillance procedures to include verification of green and amber test lights 3t panel 5B032B during restoration and revising Operations and l&C surveillance procedures to include verification that ontacts for relays that have actuated during the test have changed back to their normal state, prior to test restoration.
dditional corrective actions include revising the procedure preparation process, improving the screening and incorporation Df Operating Experience, improving lesson plans, conducting training, placing operator aids adjacent to the Multiplexer Test Switch, and requiring an inspection on other master relays.
I.
DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S)
The systems and components affected by this event include the reactor protection system (RPS) and the solid-state protection system (SSPS).
The RPS at Callaway Plant initiates a unit shutdown, based on the values of selected unit parameters, to protect against violating the core fuel design limits and reactor coolant system pressure boundary design limits dunng anticipated operational occurrences and to assistthe Engineered Safety Features systems in mitigating accidents.
2.
INITIAL PLANT CONDITIONS
Callaway was in MODE I at approximately 100% rated thermal power atthe time ofthis event. No major safety related systems were out of service.
3.
EVENT DESCRIPTION
On January 7, 2022 at 1223 with the reactor at approximately 100% rated thermal power, the reactor automatically tripped as a result of a set of contacts internal to SSPS B train Master Relay SB032CK524 that failed to close. Safety systems functioned as expected. The Operations staff responded to the event in accordance with applicable plant procedures. An ENS notification (EN 55698) was made forthis event at 1629 hours0.0189 days <br />0.453 hours <br />0.00269 weeks <br />6.198345e-4 months <br /> on January 7, 2022.
Pnorto the reactortrip, Operations and Instrumentation and Control (l&C) personnel coordinated the performance of ISF-SB-00A32, SSPS Tm B Functional Test, and OSP-SB-0001 B, Reactor Trip Breaker B Trip Actuating Device Operational Test, to perform regularly scheduled Technical Specification surveillances on the B Train Solid State Protection System and B Train Reactor Trip Breaker. All steps in both procedures were performed as written, with I&C completing ISF-SB-00A32 as briefed priorto the performance of Section 6.4 of OSP-SB-0001 B.
Wth l&C testing completed, Operations proceeded with the performance of Section 6.4 forthe Trip Breaker B Trip Actuating Device Operational Test(TADOT), which closes Reactor Trip Breaker Bypass Breaker B in orderto conduct testing that opens Reactor Trip Breaker B. By design, closing Reactor Trip Breaker Bypass Breaker B creates a General Warning signal which has the potential to trip the reactor if a second General Warning signal is received. Aftertesting was completed and during the restoration of Section 6.4, once Reactor Trip Breaker B was closed, Reactor Trip Breaker Bypass Breaker B was opened.
In accordance with OSP-SB-0001 B, Operations verified that Annunciator 76A, SSPS B GENERAL WARNING, was clear and that the General Warning red light on panel SBO29B for SSPS Train B was off. These indications led Operators to believe that the General Warning signal was no longer present, and consequently, the Operators proceeded on with Step 6.4.45 to return the multiplexer test switch through Inhibit to the A+B position at 5B029B. Moving the multiplexer test switch through Inhibit is known to generate a second General Warning signal, butthis is required to restore SSPS to the normal configuration. When Operations performed Step 6.4.45 to place the multiplexertest switch through Inhibit at 5B029B, a reactortrip occurred unexpectedly.
Per plant design, an auxiliary feedwater system actuation occurred as expected in response to the reactortrip. Also, consistent with plant response to a reactortrip from a high power level, a main feedwater isolation signal was generated.
Following the reactor trip, an erratic position indication was observed for one feedwater isolation valve, butthe valve was subsequenily confirmed to be closed. In addition, one intermediate range nuclear instrumentation channel failed. Other nuclear instrumentation channels functioned correctly to indicate the shutdown state ofthe reactor. These failures did not complicate the(08-2020)
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Esmated 3 LERN1RIBER YEAR SEQUENTIAL REV Callaway Plant, Unit No. 1 05000-483 NUMBER NO.
2022
- - 001
- - 00 7.
urcr I VIZ ACTIONS Corrective Actions include revising Operations surveillance procedures to include verification of green and ambertest lights at panel SBO32B (A) prior to operation ofthe multiplexertest switch and revising Operations and l&C surveillance procedures to include verification that contacts for relays that actuated during the test have changed back to their normal state pnorto test restoration.
Additional corrective actions include revising the procedure preparation process, improving the screening and incorporation of Operating Experience, improving lesson plans, conducting training, placing operator aids adjacentto the multiplexer test sMtch, and requiring an inspection on other master relays.
8.
PREVIOUS SIMILAR EVENTS
No previous occurrences of a reactor trip due to inadequate verification that a B (A) train general warning trip signal did not exist prior to the operation ofthe A (B) train multiplexer test switch have occurred at Callaway Plant. There were three previous occurrences of reactortrips that occurred in 2020 (listed below), butthere is no commonality in the causes of those reactortrips in comparison tothe cause ofthe reactortrip described in this LER.
1.
LER 2020-002, Reactor Trip and AFW Actuation Following Spurious MFRV Closure, submitted via Ameren Missouri letter ULNRC-06585, dated June 3, 2020 (Accession Nos. ML20155K872, ML20155K873) 2.
LER 2020-006, Reactor Trip due to Main Generator Ground Fault, submitted via Ameren Missouri letter ULNRC-06620, dated November 25, 2020 (Accession Nos. ML20330A266, ML20330A267) 3.
LER 2020-008, Reactor Trip due to Main Generator Ground Fault, submitted via Ameren Missouri letter ULNRC-06638, dated February 18, 2021 (Accession No. ML21049A109)Pageof 4