05000277/LER-2024-003, Automatic Reactor Scram Following Main Turbine Trip Due to Degraded Condenser Vacuum

Automatic Reactor Scram Following Main Turbine Trip Due to Degraded Condenser Vacuum

ML24249A109
Person / Time
Site:	Peach Bottom
Issue date:	09/05/2024
From:	Stiltner R Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
ENS 57221, CCN: 24-45 LER 2024-003-00
Download: ML24249A109 (1)

LER-2024-003, Automatic Reactor Scram Following Main Turbine Trip Due to Degraded Condenser Vacuum

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
2772024003R00 - NRC Website

text

10 CFR 50.73 CCN: 24-45 September 05, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 2 Subsequent Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277 Subject:

Licensee Event Report (LER) 2024-003-00 Automatic Reactor Scram Following Main Turbine Trip due to Degraded Condenser Vacuum Reference:

ENS 57221 The subject report is being submitted in accordance with 50.73(a)(2)(iv)(A) for actuation of the Reactor Protection System and Containment Isolation signals.

There are no commitments contained in this letter. If you have any questions, please contact the Peach Bottom Regulatory Assurance Engineer, Ms. Amy Huber at (267) 533-7247.

Respectfully, Ryan C. Stiltner Plant Manager Peach Bottom Atomic Power Station Enclosure cc:

USNRC, Administrator, Region I USNRC, Senior Resident Inspector W. DeHaas, Commonwealth of Pennsylvania S. Seaman, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-Owner Affairs Stiltner, Ryan C

Digitally signed by Stiltner, Ryan C Date: 2024.09.05 07:34:00

- 04'00'

Abstract

While conducting power ascension following a maintenance outage, Peach Bottom Unit 2 began experiencing increasing condensate pump discharge chlorides because of a condenser tube leak. A condenser water box was isolated to facilitate repairs, but due to high river temperatures combined with elevated offgas inleakage, the water box isolation resulted in degrading condenser vacuum. Attempts to restore vacuum were unsuccessful and ultimately required a trip of the main turbine.

Because the Reactor Protection System (RPS) input for Turbine Stop Valve (TSV) and Turbine Control Valve fast (TCV) closure was armed, the turbine valve closure generated a scram signal. Group II and III Primary Containment Isolation Valves isolated because reactor water level reached the isolation setpoint. Reactor water level was maintained with feedwater and pressure was maintained with bypass valves. The scram occurred without complication and all systems responded as expected. Unit 3 was not impacted by this event.

This event is reportable under 10CFR50.73(a)(2)(iv)(A) due to manual or automatic isolation of systems listed in 10CFR50.73(a)(2)(iv)(B) including RPS and containment isolation signals. An ENS notification was made within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the event, reference ENS 57221.

(See Page 2 for required number of digits/characters for each block)

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) Page 3 of 3 Previous Similar Events In February 2004, Peach Bottom manually scrammed due to decreasing condenser vacuum. The cause of the loss of vacuum was inleakage of non-condensable gases from a crack in a feed pump turbine expansion joint.

Ref. LER 2004-002-00, dated 4/30/2004.

In August 2022, Peach Bottom experienced condenser vacuum degradation during a load drop in support of condenser cleaning activities, after isolating condenser water boxes. In this case, conditions were stabilized without requiring a trip of the main turbine or a reactor scram. Increased offgas flow was not a factor in this event.