05000247/LER-2006-002
| Indian Point 2 | |
| Event date: | 7-24-2006 |
|---|---|
| Report date: | 9-22-2006 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2472006002R00 - NRC Website | |
DESCRIPTION OF EVENT:
Note: The Energy Industry Identification System Codes are identified within brackets { } On July 24, 2006, PAM instrument LT-3300 {IP} was determined to be inoperable. This determination was made when reviewing data taken during a July 22, 2006 containment pressure relief that reduced containment pressure from 0.6 psig to -0.1 psig. The containment level transmitter LT-3300, which indicates sump water level, unexpectedly responded to changes in containment pressure. As containment pressure lowered there was an increase in indicated sump level from 40.8 feet to 41.3 feet. This event was recorded in the IPEC corrective action program as CR-IP2-2006-04402. It was subsequently determined that LT-3300 had been inoperable since May, 16, 2006, the date Unit 2 exceeded Mode 3 upon startup from the 2R17 refuel outage.
The instrument, LT 3300, was one of three containment water level (containment sump) instruments required to be operable in accordance with TS 3.3.3. The other two required PAM instruments were LT-940 and LT-941.
However, LT-940 had previously been declared inoperable upon exceeding Mode 3 during startup from refuel outage 2R17 on May 16, 2006. Therefore, two required channels had been inoperable since May, 16, 2006. This time period exceeded the TS 3.3.3 Post Accident Monitoring Instrumentation, Condition C, 7 day completion time to restore all but one channel to operable status. In addition, entry into Mode 3 on May 16, 2006, and subsequent return to full power, was made with these two channels inoperable without meeting the requirements of LCO 3.0.4. Therefore, a reportable condition was determined to exist pursuant to 50.73(a)(2)(i)(B).
An evaluation was conducted and the following sequence of events that occurred during and following refueling outage 2817 was identified:
- During the 2R17 outage (April/May, 2006), as part of a containment building sump upgrade, LT-3300 was removed and reinstalled. LT-3300 consists of a Barton {B080} Model 764 differential pressure electronic transmitter {LT}, high and low pressure taps, a test connection line with isolation valve and test connection, and a remote operated isolation valve. The transmitter and instrument tubing were removed and re-installed as a unit. The high and low pressure taps attached to the transmitter are sealed. The test line and remote isolation line were disassembled and reassembled in the upgraded sump and pressure tested satisfactorily.
- During the 2R17 outage repairs were made to the LT-3300 installation to resolve tubing air leaks. The repairs were determined to be successful by leak test and proper slope, proper support and absence of kinks.
- On May 13, 2006 LT-3300 was satisfactorily calibrated.
- A review of previous IPEC condition reports written against LT-3300 identified a condition, identified in 1999, where indicated level was dependent on containment pressure. The corrective action was to vent the instrument lines, which was completed during the 2R13 refueling outage.
- A review of previous industry condition reports written against Barton Model 764 transmitters did not identify any additional relevant information.
- A review of LT-3300 transmitter data showed that the instrument had been responding to containment pressure changes as early as May 18, 2006.
- An extent of condition review was conducted. Only one other Barton 764 transmitter is in service. It is a recirculation sump level transmitter and shows no signs of influence of containment pressure.
LT-3300 is located inside the crane wall in an elevated radiological field and heat stress area. Therefore, troubleshooting and repair of LT-3300 cannot reasonably be performed during plant operation. These activities were deferred until 2R18 refuel outage that would allow access to conduct the troubleshooting, repair or replacement activities.
On August 23, 2006 during a forced outage, a visual inspection of LT-3300 was conducted. There was no visible damage or kinks to the capillary tubing or other obvious indications.
CAUSE OF EVENT
The apparent cause of the failure of LT-3300 is currently indeterminate as LT-3300 is not accessible during higher modes of operation.
CORRECTIVE ACTIONS
The following corrective actions have been or will be performed under the Corrective Action Program (CAP)to address the causes of this event and prevent recurrence:
- The troubleshooting and replacement or repair of LT-3300 has been scoped as 2R18 outage work.
- The cause of LT-3300 inoperability will be evaluated following troubleshooting and replacement or repair of LT-3300.
EVENT ANALYSIS
The event is reportable under 10CFR50.73(a)(2)(i)(B). The licensee shall report any event or condition which was prohibited by the plant TS. This event meets the reporting criteria because two containment water level (containment sump) instruments required to be operable in accordance with TS 3.3.3 were determined to be inoperable for greater than the TS allowed completion time of 7 days. The requirements of TS 3.3.3, Condition C, were not met from May 16, 2006, until LT-940 was removed from the TS on July 28, 2006 via an emergency TS amendment (TS Amendment No. 249). The amended TS allow for continued operation with one of two channels inoperable. In addition, entry into Mode 3 on May 16, 2006, and subsequent return to full power, was made with these two channels inoperable without meeting the requirements of LCO 3.0.4.
PAST SIMILAR EVENTS
A review of the past two years of Licensee Event Reports (LERs) was performed for events that involved inoperable components that exceeded the TS allowed completion time and identified two issues when AOTs were exceeded. LER 2005 001 described an event where an auxiliary component cooling water pump was determined to be inoperable due to an improperly serviced discharge check valve. LER 2005-002 described an event where one train of ECCS was inoperable due to gas intrusion from a leaking check valve.
SAFETY SIGNIFICANCE
This event had no effect on the health and safety of the public.
There were no actual safety consequences for the event because there were no accidents or transients requiring the use of these instruments.
There were no significant potential safety consequences of this event under reasonable and credible alternative conditions. The TS in force at the time of the event specified three required channels (LT-940, LT-941 and LT-3300) for the containment sump water level instrumentation. Subsequent to the event a TS amendment was approved that specifies two required channels (LT 941 and LT-3300). The amended TS allows for continued operation with one of these two channels inoperable provided a report is submitted to the NRC pursuant to TS 5.6.6. This report was provided on August 7, 2006 (NL-06-083).
The amended TS represents a safe operating condition and mirrors the configuration of the plant covered by this event report (LT-941 operable, LT 3300 inoperable). Therefore, the plant was in a safe operating condition during the event.