ENS 42116
ENS Event | |
|---|---|
21:00 Nov 3, 2005 | |
| Title | Ts Required Components Inadvertently Rendered Inoperable Due to Inadequate Review of Work Clearance |
| Event Description | At 0200 on 11/03/05 a clearance was authorized that defeated the DW [Drywell] pressure high and Rx [Reactor] vessel low isolation features to valves in the Nuclear Closed Cooling System and Instrument Air Systems. The required T.S. [Technical Specification] actions after this discovery are that the plant should have been in Mode 3 at 1600 on 11/3/05. The clearance was removed and the circuit restored to operability at 0142 on 11/4/05. The time of discovery for the loss of safety function was 2345 on 11/3/05.
The clearance was to perform pre-planned maintenance activities. The licensee plans on entering this incident into their corrective action program and will issue a Condition Report. The licensee informed the NRC Resident Inspector.
An 8-hour notification was made on November 3, 2005, in accordance with 10CFR50.72(b)(3)(v)(D), Accident Mitigation. This report was made when it was discovered that a clearance had unintentionally deenergized a portion of the containment isolation logic. This logic would have prevented a containment isolation valve for the nuclear closed cooling system and a containment isolation valve for the instrument air system from closing on a signal due to high drywell pressure or reactor vessel low level as designed. The condition was determined not to be a loss of containment (leakage) function since each containment penetration also has an inboard containment check valve which is leak tested and is credited for preventing leakage. The check valves in both penetrations were successfully tested to be in conformance with 10 CFR 50 Appendix J Option B criteria in March 2005. The containment isolation (instrumentation) function was also not lost. Only the logic for Group 2A outboard valves was deenergized. This was a small portion of the outboard logic and had no impact on the inboard logic. Since neither the containment function nor the containment isolation function was lost, there was no loss of safety function for an accident mitigation function and ENF 42116 Is retracted. As discussed in ENF 42116, a Technical Specification violation occurred and is reportable per 10CFR50.73(a)(2)(i)(B), as a condition prohibited by Technical Specifications." The licensee will be submitting a written LER for the 10CFR50.73(a)(2)(i)(B) event. The licensee notified the NRC Resident Inspector. Notified the R3DO (Hills). |
| Where | |
|---|---|
Perry  Ohio (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+6.53 h0.272 days <br />0.0389 weeks <br />0.00894 months <br />) | |
| Opened: | Robert Kidder 03:32 Nov 4, 2005 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Dec 30, 2005 |
| 42116 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |