05000352/LER-2003-001
| Docket Number | |
| Event date: | 01-31-2003 |
|---|---|
| Report date: | 04-01-2003 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 3522003001R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 1 was in Operational Condition (OPCON) 1 (Power Operation) at approximately 100% power. There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On January 31, 2003, at approximately 10:30 hours, an engineer discovered that a cleanout plug was not properly installed in a dirty radwaste drain (EIIS:DRN) line embedded in the floor of the lA / 1C residual heat removal (RHR) (EIIS:EO) pump room. The plug was found resting on the opening but the threads were not engaged. The system engineer then consulted with the subject matter expert on flooding to determine the potential impact. Operations shift management was informed of the condition at approximately 13:00 hours. The plug was subsequently reinstalled by maintenance.
Operations shift management determined that the issue was reportable and completed the required 8-hour NRC ENS notification at 19:55 hours. The condition was reported under 10CFR50.72(b)(3)(ii) due to a condition that results in the plant being in an unanalyzed condition that significantly degrades plant safety.
An investigation determined that the floor drain line cleanout plug was most likely improperly installed following a hydrolazing activity that was performed on the lA RHR Heat Exchanger during the prior Unit 1 refueling outage in March 2002. The lA RHR and 1C RHR were affected by the flood barrier breach for approximately 11 months, which exceeds the Technical Specifications (TS) allowable outage time (AOT) specified in several TSs.
The TS AOT for ECCS (3.5.1), Suppression Pool Cooling (3.6.2.3), Suppression Pool Spray (3.6.2.2), Primary Containment Hydrogen Recombiner Systems (3.6.6.1) and TS 3.0.3 were exceeded if it is assumed that lA and 1C RHR pumps were inoperable due to the degraded flood barrier. In addition, the 1B RHR pump was concurrently inoperable for planned maintenance for approximately 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> and 1D RHR pump was concurrently inoperable for planned maintenance for approximately 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> during the above 11 month period.
A qualitative analysis of the risk impact of this condition was performed. The analysis determined that the likelihood of flooding both Unit 1 RHR rooms to a level that would render all four pumps unavailable is low. The analysis assumes that operators would be capable of taking mitigating actions and prevent the 1A / 1C RHR room from flooding to a level that would adversely affect the 1A and 1C RHR pumps. Therefore, this condition is not considered an unanalyzed condition that significantly degrades plant safety and is not reportable under 10CFR50.73(a)(2)(ii)(B).
This event involved an operation or condition that was prohibited by the plant's TS. 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 cleanout plug is located in a dirty radwaste drain line that is embedded in the concrete floor of the 1A / 1C RHR room on reactor enclosure 177 elevation. This is the lowest elevation in the Reactor Enclosure. The line is designed to route drainage from higher elevations to the reactor enclosure dirty radwaste sump located on 177 elevation. The dirty radwaste sump collects inputs into the reactor enclosure floor drains. The clean radwaste sump collects inputs from the reactor enclosure equipment drains.
The flood analysis assumes the capacity of the reactor enclosure sumps will be exceeded and the surrounding corridor will then flood. The emergency core cooling systems (ECCS) rooms are protected from back flooding through the floor drains by check valves. The affected line is from a higher elevation and it is not equipped with a check valve. If the sumps are flooded the affected drain line would back flood the 1 A / 1C RHR. room through the missing cleanout plug If a flooding event is postulated to occur in the 1B / 1D RHR room, with the cleanout plug not installed in the lA / 1C RHR room and no operator action assumed, then both RHR rooms would flood and all four RHR pumps would become unavailable. The moderate energy line break (MELB) analysis (UFSAR 3.6.1, Postulated Piping Failures in Fluid Systems) assumes that only one ECCS room would flood and the safe shutdown of the reactor would not be prevented.
The design basis leak for the 1B / ID RHR room is a crack in the RHR suction pipe between the suppression pool wall and the RHR suction primary containment isolation valve (PCIV). This would result in an unisolable leak of 225 gpm entering the 1B / ID RHR room. It would take approximately 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br /> for the 1B / 1D RHR room to equalize with the suppression pool with level reaching 17.4 feet in the RHR room.
Cross compartment flooding on reactor enclosure 177 elevation is not assumed in the plant probabilistic risk analysis (PRA) based on the plant design using water tight compartments to protect redundant safe shutdown equipment. Therefore a quantitative risk assessment of this condition could not be performed. A qualitative risk assessment was performed and determined that the risk of all four RHR pumps becoming unavailable was insignificant.
The basis for this assessment is that the initiating event frequency of a flood in the 1B / 1D RHR compartment is low. The initiating event also has a low probability of being unisolable In addition, it is likely that operations personnel would be able to identify and terminate a dual- compartment RHR flooding event prior to exceeding the Maximum Safe Operating (MSO) water level in both RHR rooms given that both pump rooms have flood alarms (EIIS:LA) (setpoint 3.25 inches) in the main control room (MCR) and the estimated length of time to flood both rooms.
Cause of the Event
The work order detail for the refueling outage hydrolazing activity did not provide clear direction on how to dispose of the water. As a result, it is likely that the work team chose to use the drain line cleanout.
No procedure provides direction for use of the drain line cleanouts.
The drain line cleanouts do not have labels that identify them as hazard barriers.
Corrective Action Completed The affected Unit 1 reactor enclosure drain line cleanout plug has been properly installed.
All of the Unit 1 and Unit 2 reactor enclosure 177 elevation drain line cleanout plugs were verified properly installed.
All of the Unit 1 and Unit 2 reactor enclosure 177 elevation drain line cleanout plugs were labeled to indicate that a barrier breach permit is required to remove the plug.
Corrective Actions Planned An evaluation will be performed to identify the population of drain line cleanouts that should be controlled by the barrier breach program. This action will be complete by June 15, 2003.
The barrier breach program procedure will be revised to include the appropriate drain line cleanouts. This action will be complete by September 16, 2003.
Previous Similar Occurrences There were no previous occurrences of RHR inoperability due to improperly restored drain line cleanout plugs.
Component data:
System: � WD (Liquid Radwaste Management System) Component: � DRN (Drain) Manufacturer: � Z010 (Zurn) Model number: � Z-1380-2-76