05000498/LER-2023-004, Condition Prohibited by Technical Specifications Due to Inoperable Train of Essential Chilled Water
| ML24036A352 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/05/2024 |
| From: | Capristo A South Texas |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NOC-AE-24004012 LER 2023-004-00 | |
| Download: ML24036A352 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4982023004R00 - NRC Website | |
text
U:T South Tens Profect Electric GeneratinE Station PO. &ox 289 Wadsworth, Texas 77483 February 5,2024 NOC-AE-24004012 10 cFR 50.73 STI: 35555690 File No. G26 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 South Texas Project Unit 1 Docket No. STN 50498 Licensee Event Report 2023-004-00 Condition Prohibited by Technical Specifications Due to lnoperable Train of Essential Chilled Water Pursuant to reporting requirements of 10 CFR 50.73(a)(2)(iXB), STP Nuclear Operating Company (STPNOC) hereby submits the attached South Texas Project (STP) Unit 1 Licensee Event Report (LER) 2023-004-00. Causal investigation is ongoing. Once completed, a supplement to this LER will be provided.
The event did not have an adverse effect on the health and safety of the public.
There are no commitments in this submittal lf there are any questions on this submittal, please contact Tim Hammons at 361-972-7347 or me at 361-972-7697.
Aldo Ca Executive VP and CAO
Attachment:
LER 2023-004-00, Condition Prohibited by Technical Specifications Due to lnoperable Train of Essential Chilled Water Regional Administrator, Region lV U.S. Nuclear Regulatory Commission 1600 E. Lamar Boulevard Arlington, TX 7601 1 -451 1 cc:
NOC-AE-24004012 Attachment Attachment LER 2023-004-00 Condition Prohibited by Technical Specifications Due to lnoperable Train of Essential Chilled Water
Abstract
On 11120123 at '1530 Essential Chiller 12C was declared OPERABLE following maintenance. The following day at 1245, Train 'C' Essential Chilled Water System (EChWS) was declared inoperable due to excessive chilled water leakage. A subsequent Engineering evaluation determined that due to the leakage, Train 'C' EChWS should be considered inoperable from the date and time the 12C Essential Chillerwas restored from maintenance and declared OPERABLE. With only two EChWS loops OPERABLE, Technicalspecification (TS)3.7.14Action a requires restoration of the inoperable loopwithin 7 days or application of the Configuration Risk Management Program (CRMP), or to be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The Engineering evaluation determined that Train'C' EChWS was inoperable without any of the required TS actions taken from 1530 on 111201231o 1245 on 11128123 when the CRMP was entered. This is a total of 189 hours0.00219 days <br />0.0525 hours <br />3.125e-4 weeks <br />7.19145e-5 months <br /> and '15 minutes which exceeds the 174 hours0.00201 days <br />0.0483 hours <br />2.876984e-4 weeks <br />6.6207e-5 months <br /> (7 days plus 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />)allowed by theTS. Therefore, this event is reportable under 10CFR50.73(a)(2)(i)(B)asaconditionwhichisprohibitedbytheplant'sTS.Causal investigationisongoing.A supplement to this LER will be submitted upon completion of the causal investigation.
12107123 (1639) - Shift Manager concurrence that the event was reportable was obtained following completion of an Engineering evaluation which determined the excessive Essential Chilled Water'C'train leakage would render the system incapable of meeting its safety-related function for a prolonged duration beginning with the time of completion of maintenance on 11120123 (1530).
E. Method of Discovery
The excessive chilled water leakage that led to the inoperability of Essential Chilled Water'C' train was self-revealing Following Engineering evaluation, it was discovered that the Technical Specification Action statements for Essential Chilled Water were not met.
ll. Component Failures
A. Failure Mode, Mechanism, and Effects of Failed Component
Chilled water leakage was found to have been from the chiller evaporator end bell gaskets. The condition report associated with this event discusses increased leakage from the 12C Essential Chiller Expansion Tank level for three months prior to this event. The Engineering evaluation for this event concluded that the leak rate occurring in the three months leading up to this event was within acceptable limits. However, the leak rate increased significantly from 11120124 to 11121124. The Engineering evaluation of this increased leakage concluded that the leakage rendered the system incapable of meeting its safety-related function for a prolonged duration, beginning with the time after the maintenance ending on 11120123 at 1530 and recommended that the system be considered to have been inoperable from 11120123 al 1530 until 1213123 al2254.
B. Cause of Component or System Failure
Causal analysis is ongoing. A supplement to this report will be provided detailing causes upon completion of the causal analysis.
C. Systems or Secondary Functions That Were Affected by the Failure of Components with Multiple Functions
lnoperability of Essential Chilled Water'C' train rendered the 'C' train of the following systems inoperable: High Head Safety lnjection, Low Head Safety lnjection, Containment Spray, Control Room Envelope HVAC.
D. Failed Component lnformation System: Chilled Water System {KM}
Component: Chiller Unit iCHU)
Manufacturer: York {Y01 8}
Model: OTKSC1 -IMCS-R1 1 lll. Analysis of Event A. Safety System Responses that Occurred No safety system responses occurred because ofthis event.
B. Duration of Safety System lnoperability Essential Chilled Water Train 'C' was inoperable from 1530 on November 20,2023,1o 2254 on December 3, 2023. This was a total of 319 hours0.00369 days <br />0.0886 hours <br />5.274471e-4 weeks <br />1.213795e-4 months <br /> and 24 minutes.
C. Safety Consequences and lmplications A risk evaluation was performed to estimate the lncremental Core Damage Probability (ICDP) associated with this event.
The calculated ICDP is above the Non-Risk Significant threshold but below the Potentially Risk Significant threshold.
The event did not result in any offsite release of radioactivity or increase of offsite dose rates and there were no personnel injuries or damage to any other safety-related equipment associated with this event.
Therefore, there was no adverse effect on the health and safety of the public.
lV. Cause of Event Causal analysis is ongoing. A supplement to this report will be provided detailing causes upon completion of the causal analysis.
V. Corrective Actions
Causal analysis is ongoing. A supplement to this report will be provided detailing significant corrective actions upon completion of the causal analysis.
Vl. Previous Similar Events STP Nuclear Operating Company submitted two Licensee Event Reports in January 2024 associated with the Essential Chilled Water System. Unit 1 LER 2023-003-00 was submitted on 1109124 and Unit 2 LER 2023-001-00 was submitted on 01115124. Each event was reported under 10 CFR 50.73(aX2)(v)(D) as a condition that could have prevented fulfillment of a safety function which is a different reporting criteria than this event (10 CFR 50.73(aX2XiXB)) STPNOC is performing additional cause evaluations to determine if any common causes exist between this event and the other two Essential Chilled Water System events.
NRC FORM 3664 (10-01-2023)