05000354/LER-2005-005
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. | |
| Event date: | 06-28-2005 |
|---|---|
| Report date: | 08-29-2005 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3542005005R00 - 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: June 28, 2005 Discovery Date: June 28, 2005
CONDITIONS PRIOR TO OCCURRENCE
During the periods of 'A' CREF inoperability, Hope Creek was in operational condition 1. On January 29, 2005, first day of exceeding TS 3.7.2, Hope Creek was at approximately 44% reactor power. There was no additional equipment out of service that impacted this event.
DESCRIPTION OF OCCURRENCE
On June 28, 2005, a review of logs associated the operation of the 'A' CREF train {KM} identified that in January 2005 and February 2005 that the 'A' CREF train was inoperable for greater than the Hope Creek Technical Specification 3.7.2 allowed outage time of 7-days.
A review of maintenance work for the 'A' CREF chilled water system {VI} identified that maintenance was performed on 'A' CREF train on January 11, 2005 to replace the evaporator vent valve, which required the filling and venting of the chilled water system. On January 13, 2005, the 'A' CREF train was restored to operable following maintenance. The 'A' CREF train was placed in standby on January 15, 2005 until it was placed in service on February 1, 2005.
On February 1, 2005, at 1616 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.14888e-4 months <br /> the 'A' CREF train tripped shortly after being placed in service when the 1AP400 control room chilled water pump tripped. At 0048 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> on February 2, 2005, the 1AP400 control room chilled water pump was placed in service and tripped approximately 30 seconds later. The 'A' chilled water loop was filled and vented and the 'A' CREF train restored to operable at 0147 hours0.0017 days <br />0.0408 hours <br />2.430556e-4 weeks <br />5.59335e-5 months <br /> on February 3, 2005. The 'A' CREF train was placed in standby on February 8, 2005 until it was placed in service on February 25, 2005.
On February 25, 2005, the 'A' CREF train tripped when it was placed in service. Shortly after being placed in service, the 1AP400 control room chilled water pump tripped with an indication of low flow. The 'A' chilled water loop was filled and vented. On February 27, 2005, the 'A' CREF train was returned to an operable but degraded status. The operability determination provided direction that when the 'A' CREF train was placed in standby configuration for greater than 7 days without filling and venting that the train would be declared inoperable. With the train in standby for extended periods of time, the air that was entrained in the system is allowed to come out of solution and collect in various high points throughout the system. These air pockets migrate throughout the chilled water system on a pump start causing either the flow transmitter to sense low flow, or pump performance to degrade which may result in a trip of the chilled water circulating pump.
- Based on the review of logs and the actions from the operability determination to declare the 'A' CREF train inoperable when in standby greater than seven days without filling and venting, the 'A' CREF train was inoperable during the periods of January 22 to February 3, 2005 and February 15 to February 27, 2005 which exceeds the TS 3.7.2 allowed outage time of 7 days. As discussed in LER 354/05-007-00, the 'B' CREF train was inoperable from January 2005 to June 2005.
With both trains of CREF inoperable for greater than one hour the requirement of TS 3.0.3 was also exceeded.
This event is being reported in accordance with 10CFR50.73(a)(2)(i)(B) as a, "condition which was prohibited by the plant's technical specifications?
CAUSE OF OCCURRENCE
The cause of the inoperability of the 'A' CREF train was the entrainment of air in the chilled water train following maintenance on the evaporator. The entrainment of air in the system was due to inadequate filling and venting of the chilled water train.
PREVIOUS OCCURRENCES
A review of LERs at Hope Creek for the previous two years was performed. This review identified the following LERs associated with CREF train inoperability: 354/03-002-00, 354/04-002-00, 354/04-003-01, 354/04-005-00, 354/05-004-00 and 354/05-007. Although these LERs were against the CREF system, the reportable occurrences were not associated with improper filling and venting. Corrective actions for these LERs were specific to the events and would not have prevented the inoperability of the CREF train due to air entrainment. There were no LERs in the previous two years for Hope Creek associated with improper filling and venting of a system.
SAFETY CONSEQUENCES AND IMPLICATIONS
During the period of time the 'A' CREF train was assumed to be inoperable, the 'B' CREF train was also inoperable. No plant events occurred during the period of time that the 'A' CREF was assumed inoperable that required the actuation of the CREF system.
As discussed in LER 354/05-007-00, the 'B' CREF train was considered inoperable since the train would not have been capable of clearing the low fan flow trip during a LOP/LOCA. However, the 'B' CREF train was still capable of being started manually. In accordance with the design basis dose analysis for a LOCA event, control room operator radiological doses as evaluated in the analysis would not be exceeded if the control room envelope (CRE) is initially isolated and a CREF train is started within the first 30 minutes of the LOCA to pressurize the CRE. The 'B' CREF train would have isolated the control room envelope, the fan would have tripped on low flow, but the operators were capable of re-starting the CREF train within 30 minutes from the control room.
A review of this event determined that a Safety System Functional Failure (SSFF) has not occurred as defined in Nuclear Energy Institute (NEI) 99-02. Since the 'B' CREF train was capable of mitigating the consequences of a design basis accident in accordance with the design basis dose analysis, this event did not impact the ability to mitigate the consequences of an accident.
4 � 1. Procedure HC.OP-SO.GJ-0001, "Control Area Chilled Water System Operation," was revised on April 1, 2005 to improve the venting process for the control room chilled water system.
2. On June 3, 2005, the 'A' CREF train was returned to a fully operable status.
COMMITMENTS
This LER contains no commitments.