ENS 42542
ENS Event | |
|---|---|
00:29 May 2, 2006 | |
| Title | Low Temperature Overpressure Protection (Ltop) Trains Inoperable |
| Event Description | Event: At 2029 hours0.0235 days <br />0.564 hours <br />0.00335 weeks <br />7.720345e-4 months <br />, Oconee Unit 3 was in Mode 5 for a refueling outage. The administrative controls which comprise one train of Low Temperature Overpressure Protection (LTOP) were not yet in service, but a dedicated LTOP operator was in place as a Tech Spec required compensatory measure. Instrument Technicians performing a procedure erroneously isolated the low range RCS pressure indication, which removed the Power Operated Relief Valve (PORV) from service while required for LTOP. This placed Unit 3 in a one-hour action statement per Technical Specification 3.4.12, Condition H.
Initial Safety Significance: This is potentially a condition which could have prevented the fulfillment of a safety function (LTOP). Both the automatic PORV train and the Admin Control train were inoperable per Technical Specifications. However, a dedicated LTOP operator was in place meeting the compensatory measures requirement for continued operation per TS 3.4.12, Condition F related to the Admin Control requirement. No event occurred while in this condition which would challenge the LTOP function. Corrective Action(s): Operator at the controls recognized the loss of indication and contacted the Instrument Technicians. They verified their error and returned the instrument to service within one hour. The licensee will notify the NRC Resident Inspector.
At 0215 EDT on 5-2-06, Oconee made an ENS notification to report a condition which could have prevented the fulfillment of a safety function, specifically Low Temperature Overpressure Protection (LTOP). The LTOP Technical Specification (TS) 3.4.12 requires that a) the Power Operated Relief Valve (PORV) be operable, and b) administrative controls be in place to assure greater than 10 minutes are available for operator action to mitigate an LTOP event. As stated in the initial report, during shutdown for a refueling outage instrument technicians erroneously isolated the low range RCS pressure indication, which made the PORV inoperable for automatic operation while required for LTOP. In addition, the administrative controls were not yet fully established. However, if a specific sub-set of administrative controls are in place, the TS allows credit for a dedicated LTOP operator as a compensatory measure. Upon further review, Oconee has confirmed that a) the PORV remained available for manual initiation by the dedicated LTOP operator, and b) the dedicated LTOP operator and associated sub-set of administrative controls were in place. This satisfied the required actions of TS 3.4.12 Condition F and assured that an LTOP event could be mitigated. Therefore, Oconee concludes that this event did not constitute a potential loss of safety function. Actions were taken to restore the instrument alignment to restore automatic actuation capability for the PORV within the required action time per TS 3.4.12. Therefore there was no operation in a condition prohibited by Tech Specs. As a result, the event is not reportable under 50.72 or 50.73 and the ENS notification is hereby retracted. Corrective Action(s): As stated above, the instrument alignment was restored to return the PORV to an operable status for automatic actuation. Subsequently, the full set of administrative controls were established. As shutdown continued, the unit exited the LTOP region. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Oconee  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.77 h0.0738 days <br />0.0105 weeks <br />0.00242 months <br />) | |
| Opened: | R. P. Todd 02:15 May 2, 2006 |
| NRC Officer: | Mike Ripley |
| Last Updated: | Jun 29, 2006 |
| 42542 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |