05000352/LER-2001-001
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3522001001R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 1 was in Operational Condition (OPCON) 1 (Power Operation) at 100% power. There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On July 11, 2001 at 18:00 hours, a 24-hour endurance run surveillance test was being conducted on D12 EDG (EIIS:DG). During a fuel oil delivery approximately 1-1/2 feet of water was observed on the floor of the D12 EDG fuel oil storage tank access pit. Subsequent testing of the D12 EDG storage tank (EIIS:TK) identified that water existed but was verified to be below the fuel oil transfer pump suction. Approximately 300 gallons of water were removed from the tank.
Complete removal of the water was confirmed by chemical analysis. Sampling and subsequent analysis verified that no water was transferred to the D12 EDG fuel oil day tank.
Inspection of the other EDG fuel oil storage tank access pits identified approximately 2 feet of water in the Dll EDG fuel oil storage tank access pit. Subsequent testing of the Dll EDG storage tank identified that water existed but was verified to be below the fuel oil transfer pump suction. Approximately 1,680 gallons of water were removed from the tank. Complete removal of the water was confirmed by chemical analysis. Sampling and subsequent analysis verified that no water was transferred to the Dll EDG fuel oil day tank.
The D13 EDG fuel oil storage tank access pit had approximately half a foot of water in the access pit. Testing verified that no water entered the D13 fuel oil storage tank. D14, D21, D22, D23, and D24 EDG fuel oil storage tank access pits had accumulations of ground water on the pit floors that did not exceed 2 inches.
Inspection of the EDG fuel oil storage tank access pits identified that the gate valve portion of D11, D12 and D13 EDG access pit drain valves was open. This allowed storm drain water to backfill the pits by leaking past the check valves in the drain line.
TS SR 4.8.1.1.2.b.2 requires that water in the EDG fuel oil storage tank be removed every 31 days. Water is believed to have existed in the Dll and D12 EDG fuel oil storage tanks during the surveillance tests that were conducted on July 2, 2001 (D11) and June 5, 2001 (D12). Since the surveillance test did not identify the water accumulation, water was not removed as required.
This resulted in a condition prohibited by plant Technical Specifications. Since the surveillance test exceeded the 31 days and failed during subsequent performance, this is a reportable condition.
An ENS notification was made per 10CFR50.72(b)(3)(v) on July 12, 2001 at 05:29 hours. It was later determined that the quantity of water in the Dll and D12 EDG Fuel Oil Storage Tanks was below the fuel oil transfer pump suction and no water would have been transferred to the day tanks. Therefore, this condition would not have prevented the fulfillment of the safety function. This notification was retracted on September 6, 2001 at 14:07 hours.
This event involved a condition prohibited by Technical Specifications. Therefore, this LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(i)(B).
Analysis of the Event
There were no actual safety consequences associated with this event. The potential safety consequences of this event were also minimal.
The water levels in Dll and D12 EDG fuel oil storage tanks were below the level of the fuel oil transfer pump suctions. Therefore, no water was transferred to the EDG day tank nor would any have been transferred during an accident. All EDGs remained available throughout this event, therefore no risk exposure or impact on core damage frequency (CDF) occurred.
During the investigation, the standard water detection compound was determined to be not fully effective at identifying major water accumulation in the EDG fuel oil storage tank sump.
The compound changes from brown to red when it contacts water. When the detector is partially submerged in water, the boundary between the affected region and the unaffected region is marginally discernable. When the entire detection region is submerged in water as occurred in this case, the color change is not easily discernable since no contrasting line exists.
This resulted in a failure to detect water in the EDG fuel oil storage tank during previous tests for water.
Cause of the Event
This event occurred due to a detection method that was not fully effective in discerning water in the EDG fuel oil storage tank.
Corrective Action Completed A colored paste with greater color contrast is now being used to better identify the presence of water in the fuel oil storage tank.
An administrative clearance has been applied to all EDG fuel oil storage tank access pit drain valves to maintain the valves in the closed position as an interim corrective action.
Component identification numbers have been created and component identification labels have been installed for the EDG fuel oil storage tank access pit drain valves Corrective Action Planned Procedures will be implemented for control of the EDG fuel oil storage tank access pit drain valves.
Previous Similar Occurrences There were no previous occurrences of failure to detect water in the fuel oil storage tank.