05000387/LER-2023-003, D Diesel Generator Inoperable Due to Clogged Fuel Injectors
| ML23313A196 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/09/2023 |
| From: | Casulli E Susquehanna, Talen Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PLA-8093 LER 2023-003-00 | |
| Download: ML23313A196 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3872023003R00 - NRC Website | |
text
November 09, 2023 Edward Casulli Site Vice President Attn: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3795 Fax 570.542.1504 Edward.Casulli@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387(388)/2023-003-00 UNIT 1 LICENSE NO. NPF-14 UNIT 2 LICENSE NO. NPF-22 PLA-8093 TALEN~
ENERGY 10 CPR 50.73 Docket No. 50-387 50-388 Attached is Licensee Event Report (LER) 50-387(388)/2023-003-00. The LER reports a condition in which the D Diesel Generator was slow to start and reach required frequency within acceptance criteria. This condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
There were no actual consequences to the health and safety of the public as a result of this event.
This letter cqntains no new or revised regulatory commitments.
~-!is G:<-4-wy 5 *f' E. Casulli Attachment: LER 50-387(388)/2023-003-00 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 September 12, 2023, at approximately 05:01, during the performance of surveillance testing, the D Diesel Generator (DG) failed to reach the required frequency within the acceptance criteria specified in Surveillance Requirement (SR) 3.8.1.7. Operators declared SR 3.8.1.7 failed and entered Technical Specification (TS)
Limiting Condition of Operation (LCO) 3.8.1, Condition B, on both Susquehanna Steam Electric Station Unit 1 and 2 for the inoperable D DG. The other three DGs (A, B, and C) were verified to be OPERABLE and operators substituted the E DG in for the D DG. After completion of the E DG substitution, LCO 3.8.1, Condition B, was exited on September 12, 2023, at approximately 22:52.
The failure to reach the required frequency within the acceptance criteria was the result of clogged fuel injectors.
The condition of the inoperable D DG was determined to likely have existed for longer than allowed by TS, and
~he event was determined to be reportable in accordance with 10 CFR 50. 73(a)(2)(i)(B) as a condition prohibited by TS.
There were no actual consequences to the health and safety of the public as a result of this event.
CONDITIONS PRIOR TO EVENT
181 050 D
052 Estimaled
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR 05000387 2023 SEQUENTIAL NUMBER REV NO.
003 00 Unit 1 - Mode 1, approximately 100 percent Rated Thermal Power (RTP)
Unit 2 - Mode 1, approximately 93 percent RTP There were no structures, systems, or components that were inoperable at the start of the event and contributed to the event.
EVENT DESCRIPTION
On September 12, 2023, at approximately 05:01, operators started the D Diesel Generator (DG)
[EIIS Code/Component Code: EK/DG] in accordance with the applicable surveillance procedure. The D DG reached the required frequency at a time of 12.6 seconds, which exceeds the acceptance criteria of 10 seconds specified in Surveillance Requirement (SR) 3.8.1.7. Operators declared SR 3.8.1.7 failed and entered Technical Specification (TS) Limiting Condition of Operation (LCO) 3.8.1, Condition B, on both Susquehanna Steam Electric Station (SSES) Unit 1 and 2 for the inoperable D DG. The other three DGs (A, B, and C) were verified to be OPERABLE and operators substituted the E DG in for the D DG. After completion of the E DG substitution, LCO 3.8.1, Condition B, was exited on September 12, 2023, at approximately 22:52.
The condition of the inoperable D DG was determined to likely have existed for longer than allowed by TS, and the event was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
The following is a timeline of events:
February 2023 to August 2023 - The D DG has higher than normal accumulated low load run time, which was considered as a possible contributor to the clogged injectors. However, start times were acceptable after the low load operation, and there was not an increasing trend in start time.
08/17/2023 - D DG monthly surveillance start time was 8.65 seconds.
09/12/2023 - D DG monthly surveillance start time was 12.6 seconds. LCO 3.8.1, Condition B, was entered at approximately 05:01 due to the D DG being inoperable. The E DG was substituted for the D DG and LCO 3.8.1, Condition B, was exited at approximately 22:52.
09/21/2023 - Troubleshooting identified fuel injectors had excessive carbon buildup. The fuel injectors were cleaned.
09/22/2023 - D DG monthly surveillance was performed successfully with a start time of 7.95 seconds. D DG was substituted back in for the E DG and the D DG was declared operable at approximately 02: 10 on 09/23/2023.
SSES TS LCO 3.8.1 requires, in part, that four DGs are OPERABLE in MODES 1, 2, and 3. Condition B requires that an inoperable DG be restored to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or that each unit be shut down to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and MODE 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Based on the identified cause of the D DG slow start, this condition likely existed for longer than allowed by TS. As a result, this condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
CAUSE OF EVENT
[gJ 050 D
052 The cause of the slow start was clogged fuel injectors.
ANALYSIS/SAFETY SIGNIFICANCE
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR 05000387 2023 SEQUENTIAL NUMBER 003 REV
- NO.
00 As described in Section 8.3 of the Susquehanna Updated Final Safety Analysis Report (UFSAR), and required by 10 CFR 50, Appendix A, General Design Criterion 17, a single failure of a DG will not prevent safe shutdown of the units in the event of a design basis accident. While the D DG was inoperable, the three remaining DGs (A, B, and C) were aligned and operable. Therefore, the slow start of the D DG did not prevent the DGs from fulfilling their safety function.
The safety function of the DGs is to provide power to equipment as assumed in the safety analyses described in Chapter 15 of the Susquehanna UFSAR. In this case, the safety analyses assume the DGs will start in 25.1 seconds of a valid start signal. Additionally, the loading analysis for the DGs assume the Residual Heat Removal motors are loaded at 13 seconds to ensure the DG can handle the load of the large motors. The start time of 12.6 seconds observed during the September 12, 2023, surveillance test was within that assumed in the accident analyses. Therefore, the D DG was able to perform its safety function.
Based on engineering analysis, this event will not be counted as a safety system functional failure under the NRC Reactor Oversight Process Performance Indicator.
CORRECTIVE ACTIONS
Key corrective actions included all D DG fuel injectors being cleaned. Although the station had implemented vendor guidance for low load run time on the DG, Susquehanna is also taking additional actions to refine guidance on low load run times for the DGs.
COMPONENT FAILURE INFORMATION
Component Name - Diesel Generator 'D' Component Identification - 0G501 D Manufacturer - Cooper Energy Services
PREVIOUS OCCURRENCES
None. Page.1. of.1.