05000354/LER-2004-002
| Hope Creek Generating Station | |
| Event date: | 9-19-2003 |
|---|---|
| Report date: | 3-18-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3542004002R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Chilled Water System {KM)* Control Room Emergency Filtration System {VI) * Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC)
IDENTIFICATION OF OCCURRENCE
Event Date: September 19, 2003 Discovery Date: January 21, 2004
CONDITIONS PRIOR TO OCCURRENCE
- Hope Creek was in Operating Condition 1 (Power Operation), at the time of discovery. No other required structures, systems or components were inoperable at the start of this event that contributed to the event.
DESCRIPTION OF OCCURRENCE
Hope Creek Technical Specification (TS) 3.7.2, requires that two (2) independent Control Room Emergency Filtration system (CREF) {VI) subsystems to be operable. Included in each subsystem is a chilled water system to maintain the control room envelope within specified environmental limits. The BK400 chiller is a support component to one of the subsystems. With the chiller inoperable, the subsystem is therefore inoperable. TS 3.7.2, Action a., requires that the inoperable subsystem be made operable within 7 days.
On September 10 and 11, 2003, trouble shooting was performed on the BK400 chiller due to erratic behavior of the chiller. The chiller was then placed in service on September 11, 2003. The chiller operated until September 19, 2003 when removed from service and placed in standby. On October 2, the BK400 chiller was selected to start. Shortly after starting the chiller tripped on low evaporator refrigerant pressure. At 5:02 on October 2, 2003, TS 3.7.2 Action (a) was entered due to the inoperability of the BK400 chiller. Corrective maintenance performed on October 3, 2003 found that the float arm had become disengaged. The BK400 chiller was repaired and returned to operable status on October 6, 2003. Based on the erratic operation of the chiller on September 10 and 11, 2003 and the discovery of the disengaged float on October 3, 2003 it was concluded that either the float fell off when the chiller was started on October 2, 2003 or had become disengaged when the chiller was removed from service on September 19, 2003.
Based on this information the BK400 chiller was not capable of performing its design function when it was placed in standby mode on September 19, 2003. Therefore the "B" CREF train was inoperable for greater than 7 days contrary to the requirements of TS 3.7.2 The event is being reported in accordance with 10CFR50.73(a)(2)(i)(B), Any operation or condition that was prohibited by the plant's Technical Specifications.
DOCKET
Hope Creek Generating Station 05000354 CAUSE OF OCCURRENCE .
The cause of the BK400 chiller failure was due to improper maintenance activities, apparent incomplete procedures and failure to complete troubleshooting activities. The BK400 chiller high side float assembly valve and ball were replaced in May 2002 following an inspection as required by a preventive maintenance (PM) work order.
Maintenance utilized the existing procedural guidance to effect replacement of the float. On October 3, 2003, during performance of repairs of the BK400 chiller, maintenance and engineering personnel discovered the float ball arm had fallen off the shaft and the clamp key was missing. The float ball arm separated from the valve shaft due to improper torquing of the ball arm clamp. A review of procedure HC.MD-PM.GJ-0001 found limited guidance on float assembly disassembly/ reassembly and no guidance on torquing of involved fasteners.
A corrective action request was initiated to determine the cause of the float ball arm separation. The subsequent investigation determined that previous corrective maintenance performed on this chiller on September 10, 2003, due to surging problems, was prematurely terminated prior to completing a float ball inspection as requested by the engineer. This issue was attributed to a communication problem and addressed under a separate corrective action order.
Screening performed during system evaluation and corrective maintenance (CM) performed in October 2003 did not identify the TS non-compliance condition of the CREF.
PREVIOUS OCCURRENCES
A review of TS noncompliance LERs was performed. LER 354/03-002-00, entitled inoperability of Control Room Emergency Filter (CREF) subsystems due to Control Room (CR) envelope breach", dated January 12, 2003 was reviewed for applicability to operability of the BK400 chiller. This event was attributed to a ductwork access hatch opening and no correlation was found to a chiller equipment issue or operability assessments. Based on this review actions associated with that LER would not have prevented this occurrence.
SAFETY CONSEQUENCES AND IMPLICATIONS
- There were no safety consequences associated with th;s event since the "A" CREF train was operable during the period the "IT' CREF was inoperable. Additionally there were no design basis radiological releases during the period that the "B" CREF train was inoperable. Only one train of CREF is required to mitigate design basis radiological events that impact the control room envelope.
This event does not constitute a Safety System Functional Failure (SSFF) as defined in NEI 99-02.
CORRECTIVE ACTION
The corrective actions to address the identified problem are as follows:
1. The BK400 chiller was repaired and returned to operable status on October 6, 2003.
2. Maintenance procedure HC.MD-PM.GJ-0001 was revised to add guidance for proper torquing of float ball arm clamp nut using a feeler gage to assess compression of clamp.
3. An evaluation is being completed regarding reportability requirements and the reviews of inoperable equipment.
COMMITMENTS
The corrective actions cited in this LER do not constitute commitments.