05000354/LER-2001-002
| Hope Creek Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(i) |
| 3542001002R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Control Room Emergency Filtration System {VI}* Safety Auxiliaries Cooling System {CC}* * Energy Industry Identification System (EIIS) codes and component function identifier codes appear as {SS/CC}
IDENTIFICATION OF OCCURRENCE
Event Date: June 22, 2001 Discovery Date: June 22, 2001
CONDITIONS PRIOR TO OCCURRENCE
The plant was in OPERATIONAL CONDITION 1 (POWER OPERATION). At the start of this event, the 'B' train of the Control Room Emergency Filtration System was inoperable.
DESCRIPTION OF OCCURRENCE
On June 22, 2001, at approximately 1325, the 'C' emergency diesel generator (EDG) heat exchanger cooling water outlet relief valve (1EGPSV-2409C) {CC/RV} opened when two pumps were operating in the 'A' Safety Auxiliaries Cooling System (SACS) loop. The relief valve reclosed when one of the 'A' SACS loop pumps was secured. The relief valve had been installed on June 5, 2001 and was set to relieve at 120 psig instead of the design lift setpoint of 150 psig.
During a postulated design basis event with two pumps operating in the 'A' SACS loop, pressure could have exceeded the lift setpoint for 1 EGPSV-2409C, causing the valve to open. If automatic makeup to the 'A' SACS loop head tank was not available, operator action would be required to identify and correct the condition before loss of inventory resulted in loop inoperability.
At the time of discovery, scheduled maintenance was underway that prevented the 'B' train of the Control Room Emergency Filtration (CREF) System from performing its design function. Technical Specification (TS) action 3.7.2.a permits continued operation for up to 7 days with one CREF subsystem inoperable. Since the 'A' SACS loop supports the 'A' train of CREF, it is possible that neither CREF train would have been available to perform its design function during a postulated design basis event.
Upon discovery, the 'A' SACS loop was placed in a configuration that ensured system pressure would not exceed the lift setpoint for 1EGPSV-2409C. The 'A' loop was then determined to be in an OPERABLE but non-conforming condition until 1 EGPSV-2409C could be replaced with a valve with the correct setting.
DESCRIPTION OF OCCURRENCE (continued) This event is reportable as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident in accordance with 10 CFR 50.73(a)(2)(v)(D) and as a condition prohibited by plant Technical Specifications in accordance with 10 CFR 50.73(a)(2)(i)(B). An eight hour notification was made to the NRC in accordance with 10 CFR 50.72(b)(3)(v)(D) on June 22, 2001 at 2118.
APPARENT CAUSE OF OCCURRENCE
The root cause of this event was the failure to update the Bill of Material (BOM) for relief valve 1EGPSV-2409C and similar valves for the other three EDGs during the development of a design change package (DCP) in 1993. The lift setpoint for the valves had been increased from 120 to 150 psig in 1985 prior to initial plant operation, but associated engineering documents were not updated to reflect the setpoint change. The DCP was developed in 1993 to incorporate the setpoint change into affected documents, but failed to include the BOM. System Engineering personnel who prepared the DCP overlooked the BOM.
In February 2001, corrective maintenance was planned for replacement of 1EGPSV-2409C dile tc.
leakage from the installed ‘falve. Although the work package correctly stated that the replace,nent valve should be set to relieve at 150 psig, the material master (i.e., the part number) specified in the work package was obtained from the inaccurate BOM and corresponded to a relief valve with a 120 psig lift setpoint.
On June 5, 2001, the replacement valve (with the 120 psig setpoint) was installed during a scheduled 'C' EDG system outage. Nameplates attached to the replacement valve showed both the design pressure (150 psig) and set pressure (120 psig). Personnel installing the valve did not note the difference in lift setpoints between the existing and replacement valves.
SAFETY SIGNIFICANCE AND IMPLICATIONS
There were no actual safety consequences associated with this event.
During a postulated design basis event with two pumps operating in the 'A' SACS loop, pressure could have exceeded the lift setpoint for 1 EGPSV-2409C, causing the valve to open. If automatic makeup to the 'A' SACS loop head tank was not available, operator action would be required to identify and correct the condition before loss of inventory resulted in loop inoperability. Alarms in the control room would alert operators to a decrease in the water level in the 'A' SACS loop head tank and procedures are in place to provide direction to operators to respond to a loss of inventory from a SACS loop. Based on the design capacity of 1 EGPSV-2409C, operators would have approximately 5.9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to identify and correct the cause for loss of inventory from the 'A' SACS loop after receiving an alarm in the control room.
SAFETY SIGNIFICANCE AND IMPLICATIONS (continued) This event constitutes a Safety System Functional Failure (SSFF) as defined in NEI 99-02.
PREVIOUS OCCURRENCES
A review of previously reported events identified one instance within the last two years of personnel error resulting in a condition that could have prevented fulfillment of a safety function.
common supply damper in the Filtration, Recirculation, and Ventilation System (FRVS) to drift closed. The corrective actions taken for the previous event were focused on non-licensed operators and would not have been expected to preclude this event from occurring.
CORRECTIVE ACTIONS
1. Upon discovery, the 'A' SACS loop was placed in a configuration that ensured system pressure would not exceed the lift setpoint for 1 EGPSV-2409C.
2. The relief vaves on the 'A', 'B', and 'D' EDGs were verified to have the correct lift setpoint.
3. Corrective maintenance on the 'B' CREF train was completed and the system was returned to OPERABLE status.
4. Relief valve 1 EGPSV-2409C was replaced with a valve with the correct lift setpoint.
5. The incorrect BOM associated with 1EGPSV-2409A, B, C and D was removed.
6. A new BOM will be created to stock the required relief valve with a 150 psig lift setpoint.
7. Maintenance procedures will be implemented to require verification of relief valve setpoint information before installation.
8. Training will be provided to appropriate personnel on lessons learned from this event.
9. The configuration change process was revised in March 2001 and is currently in a pilot implementation phase. One attribute of the revised configuration change process is to restrict the number of people involved in preparing and approving design change packages. This ensures greater proficiency and consistency in the change package process including development of and changes to BOMs.
COMMITMENTS
The corrective actions cited in this LER are voluntary enhancements and do not constitute commitments.