05000388/LER-2021-002, Re Loss of Secondary Containment
| ML21301A000 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 10/28/2021 |
| From: | Cimorelli K Susquehanna, Talen Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2021-002-00 | |
| Download: ML21301A000 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3882021002R00 - NRC Website | |
text
Kevin Cimorelli Susquehanna Nuclear, LLC Site Vice President 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3795 Fax 570.542.1504 Kevin.Cimorelli@TalenEnergy.com October 28, 2021 Attn: Document Control Desk 10 CFR 50.73 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-388/2021-002-00 UNIT 2 LICENSE NO. NPF-22 PLA-7970 Docket No. 50-388 Attached is Licensee Event Report (LER) 50-388/2021-002-00. The LER reports an event in which the secondary containment was inoperable due to differential pressure exceeding the Technical Specification limit. The condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C) as an event or condition which could have prevented the fulfillment of a safety function.
There were no actual consequences to the health and safety of the public as a result of this event.
This letter contains no new or revised regulatory commitments.
K. Cimorelli Attachment: LER 50-388/2021-002-00 Copy: NRC Region I Mr. C. Highley, NRC Senior Resident Inspector Ms. A. Klett, NRC Project Manager Mr. M. Shields, PA DEP/BRP
Abstract
On August 30, 2021, at 09:55, operators at the Susquehanna Steam Electric Station (SSES), Unit 2, identified that Reactor Building Zone II Pressure Differential Indicator (PDI), PDI-27581, was stuck at a reading of 0.32 water column vacuum. Operators also reported difficulties opening doors in the SSES Unit 2 Reactor Building, indicating a positive secondary containment differential pressure (D/P). At this time, operators determined that a loss of the secondary containment had occurred and entered the off-normal procedure for the condition. Review of alternate indication documented from earlier that day, identified the condition likely existed longer than allowed by the Technical Specification Surveillance Requirement 3.6.4.1.1 associated Note. This condition is being reported under 10 CFR 50.73(a)(2)(v)(C) as a loss of safety function.
Secondary containment was restored to an operable status at 10:30 on August 30.
The cause of the event is under investigation and will be provided in a supplement to this Licensee Event Report with the associated corrective actions. There were no actual safety consequences associated with the described condition.
CONDITIONS PRIOR TO EVENT
Unit 1 - Mode 1, approximately 100 percent Rated Thermal Power (RTP)
Unit 2 - Mode 1, approximately 100 percent RTP At 04:00 on August 30, 2021, operators at the Susquehanna Steam Electric Station (SSES), Unit 2, identified that both the A and B Standby Gas Treatment (SGT) System Zone 2 Outside Delta Pressure Indicators, pressure differential indicators (PDIs) PDI-07554A2 and PDI-07554B2 [EIIS System/Component Codes BH/PDI], respectively, were indicating below downscale on the associated meters while the digital display was reading -0.25 water column (wc) vacuum. This is indicative of a positive differential pressure (D/P) in the secondary containment. At the time of discovery, this was believed to be an indication-only issue.
EVENT DESCRIPTION
At 09:55, while investigating the downscale indication on the A and B SGT System Zone 2 Outside Delta Pressure Indicators, PDI-07554A2 and PDI-07554B2, operators at SSES, Unit 2, identified that the SGT System Zone 2 Exhaust System Circulating Space/Outside D/P Indicator, PDI-27581 [BH/PDI], was stuck at a reading of 0.32 wc vacuum. Operators also reported difficulties opening doors in the SSES Unit 2 Reactor Building, indicating a positive secondary containment D/P. At this time, operators determined that a loss of the secondary containment had occurred and entered the off-normal procedure for the condition. Entry into Technical Specification Limiting Condition for Operation (LCO) 3.6.4.1, Condition A was evaluated and determined to be unnecessary at the time of discovery based on no known breach in secondary containment and the SGT subsystem was determined to be capable of drawing down secondary containment to 0.25 wc vacuum. This allowance is defined within the associated Note for Surveillance Requirement (SR) 3.6.4.1.1.
Subsequently, when reviewing the stuck indication on PDI-27581 in aggregate with the downscale readings on PDI-07554A2 and PDI-07554B2, it was determined firm evidence exists that secondary containment D/P was likely lost at 04:00 when PDI-07554A2 and PDI-07554B2 were identified as reading downscale. As a result, the four-hour allowance of the Note modifying SR 3.6.4.1.1 would result in the SR not met at approximately 08:00 and LCO 3.6.4.1, Condition A being entered. Because there is no redundant system to secondary containment, this event requires reporting under 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented the fulfillment of a safety function needed to control the release of radioactive material.
CAUSE OF EVENT
The cause of the event is under review and will be provided in a supplement to this Licensee Event Report (LER).
ANALYSIS/SAFETY SIGNIFICANCE
Safety significance information will be provided in a supplement to this LER.
CORRECTIVE ACTIONS
Corrective actions will be provided in a supplement to this LER.
COMPONENT FAILURE INFORMATION
Component failure information will be provided in a supplement to this LER, if applicable.
PREVIOUS OCCURRENCES
Previous occurrences will be provided in a supplement to this LER, if applicable.