05000352/LER-2006-003
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 04-11-2006 |
|---|---|
| Report date: | 6-21-2006 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3522006003R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 1 was in Operational Condition (OPCON) I (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 Saturday April 22, 2006, at 09:46 hours, the Unit 1 reactor operator identified that the suppression chamber air temperature recorder (EIIS:TR) (TR-57-122) pen was failed downscale while performing the monthly surveillance log (ST-6-107-595-1). Subsequent troubleshooting identified that the ribbon cable connector (EIIS:CON) was unseated. The connector was re seated which restored the failed indication.
The investigation reviewed the recorder chart paper and determined that the indication failed downscale on April 9, 2006 after several hours of erratic indication following replacement of the recorder chart paper.
All other main control room recorder indications were verified to be operating properly with the exception of one channel on the wide range accident monitor that was providing a valid digital reading but was recording downscale. This condition was entered into the corrective maintenance process.
Technical Specification (TS) 3.3.7.5 Accident Monitoring Instrumentation requires the instrumentation channels in Table 3.3.7.5-1 to be operable. With any channel inoperable the action in the table applies._ The table requires_one channel of suppression chamber air temperature to be Operable. Action 80 applies with no suppression chamber air temperature channels operable. Action 80 requires the channel to be restored within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or be in hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. There is firm evidence that the channel was inoperable for approximately 13 days. Therefore, the allowable outage time (AOT) was exceeded on April 11, 2006.
This event involved a condition prohibited by 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 minimal. The drywell air temperature channel remained operable during the event. Emergency operating procedures do not rely on this instrument for identifying a high temperature condition that could adversely affect primary containment barrier integrity. In fact, NUREG-1433 Rev.3, Standard Technical Specifications General Electric Plants BWR/4, does not include suppression chamber air temperature as a required accident monitoring instrument.
A redundant indication of suppression chamber air temperature on an adjacent recorder remained functional during the event. However, this indication is not environmentally qualified as required by Regulatory Guide 1.97, "Instrumentation for Light Water Cooled Nuclear Power Plants to Assess Plant Conditions During and Following an Accident," December 1975.
Therefore, this instrument may have failed under some accident conditions and is not credited as satisfying the TS requirement.
The recorder ribbon cable connector is a friction fit type connector that does not lock in place and is susceptible to displacement during chart paper replacement.
Cause of the Event
The event was caused by a failure of the recorder ribbon cable connector, which became unseated during replacement of the recorder paper. A contributing cause was the failure to detect the recorder pen failure following the chart replacement.
Corrective Action Completed The recorder ribbon cable connector was re-seated which restored the indication.
Periodic monitoring of the recorder was enhanced.
Previous Similar Occurrences There were no similar occurrences of TS noncompliance due to recorder failures.
Component data:
Component:� TR (Recorder, Temperature) Manufacturer:� L130 (Leeds & Northrup Co) Model number:� Speedomax M