05000321/LER-2020-001, A EDG Inoperable Due to Water in the Day Tank
| ML20345A083 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 12/10/2020 |
| From: | Dean S Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-20-1366 LER 2020-001-00 | |
| Download: ML20345A083 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3212020001R00 - NRC Website | |
text
.. Southern Nuclear December 10, 2020 Docket Nos.: 50-321 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Sonny Dean Vice P....idant - Plant Hatch Edwin I. Hatch Nuclear Plant Unit 1 Licensee Event Report 2020-001-00 1A EOG Inoperable Due to Water in the Day Tank Ladles and Gentlemen:
Hatch Nuclear Plant 11028 Hatch Parkway North Baxley, GA 31513 912 537 5859 tel 912 366 20n tax NL-20-1366 In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report.
This letter contains no NRC commitments. If you have any questions, please contact the Hatch Licensing Manager, Jimmy Collins at 912.453.2342.
Respectfully submitted, f
- - Hatch SD/CJC/SCM Enclosure: LEA 2020-001-00 cc:
Regional Administrator, Region II NRR Project Manager - Hatch Senior Resident Inspector - Hatch RTYPE: CHA02.004
Edwin I. Hatch Nuclear Plant Unit 1 Licensee Event Report 2020-001-00 1A EOG Inoperable Due to Water in the Day Tank
Abstract
On 5/8/20 at 1714, while taking a fuel sample from the 1A Emergency Diesel Generator (EOG) day tank, 14.73 gallons of water was found in the tank. The water was immediately drained from the day tank. Additionally, from 5/14/20 through 5/16/20, the day tank and the main fuel oil storage tank (FOST) were drained, cleaned, inspected and returned to service. A past operability review was conducted and on 12/03/20 the results concluded that the EOG would not have been able to perform its safety function with the amount of water found in the day tank.
The source of water in the day tank was from accumulated water in the FOST being pumped to the day tank during a fuel transfer system surveillance on 4/29/20. Water from an underground pipe leak had entered a nearby pull box, traversed conduit connecting to the FOST manway, collected in the manway and then seeped into the FOST through threaded connections on top of the tank.
The direct cause of the event was clogging of the FOST manway drains which allowed water to collect in the manway. There was no maintenance strategy to inspect and clean the manway drains. This was corrected by cleaning debris from the drains and implementing a maintenance strategy for periodic cleaning.
Event Description
On 5/7/20, Unit 1 was in MODE 1 at 100 percent rated thermal power. While performing an Emergency Diesel Generator (EOG) fuel oil transfer pump surveillance, standing water was observed in the manway of the 1A EOG Fuel Oil Storage Tank (FOST). Due to the standing water on the FOST, a sample of the fuel was taken and analyzed. The sample found water in the diesel fuel. Subsequently, on 5/8/20 at 1714, the associated 1A EOG day tank was sampled and 14.73 gallons of water was found. Actions were taken to immediately drain the water from the day tank. Between 5/14/20 and 5/16/20 the day tank and FOST were drained, cleaned, inspected and returned to service.
Analysis and testing were conducted in order to determine if the EOG was capable of performing its safety function with
- the quantity of water found in the day tank. It was ultimately concluded on 12/03/20 that the EOG would not have been able to perform its safety function. Since the EOG was last successfully run on 4/29/20 and water was transferred from the FOST during this surveillance, it is likely the EOG would not have been able to perform its safety function beginning on 4/29/20 once the water settled in the day tank after the EOG surveillance. The time period between 4/29/20 and when the
, water was drained on 5/8/20 exceeds the Technical Specification (TS) Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, thus making this issue reportable as a condition prohibited by TS per 1 0CFR50.73(a)(2)(i)(B).
Event Cause Analysis
Causal analysis was performed to determine the source of the water in the day tank. It concluded that standing water on i top of the 1A EOG FOST had seeped into the FOST through threaded connectors on top of the tank. The water then I
settled to the bottom of the FOST and was pumped into the day tank during the EOG surveillance on 4/29/20. The source
, of the standing water on top of the FOST was from an underground pipe leak that entered a nearby pull box and then
- flowed through conduit connecting to the FOST manway. It was found that drain holes in the FOST manway were clogged, allowing water to collect in the manway. There was no maintenance strategy to inspect and clean the manway drain holes to prevent clogging. It was also determined that the sump pump in the pull box was non-functional and that conduit seals between the pull box and the FOST manway were degraded. The non-functional sump pump and degraded conduit seals contributed to water collecting in the pull box and migrating to the FOST manway.
Safety Assessment
There were no safety consequences as a result of this event. While the 1 A EOG was not operable, both the 1 B and 1 C EDG's remained operable on Unit 1. However, due to the 1A EOG being inoperable longer than allowed by TS, this event is reportable as a condition prohibited by TS per 1 0CFR50. 73(a)(2)(i)(B).
Corrective Actions
' The FOST manway drains were cleaned. Additionally, a maintenance strategy for cleaning manway drains periodically was implemented. The pull box conduit seals, sump pump and the underground pipe leak have been repaired.
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