ENS 47892
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ENS Event | |
|---|---|
16:55 May 2, 2012 | |
| Title | Potential Unanalyzed Condition with Containment Pressure Instruments |
| Event Description | While investigating operating experience from another station it was determined that Fort Calhoun Station (FCS) is subject to similar conditions. The operating experience involved setpoint drift of safety related pressure switches beyond what had been accounted for in the station's safety analyses.
Following investigation and evaluation, it was determined that pressure switches that provide safety related signals for high containment pressure to the reactor protection system (RPS) and engineered safeguards actuation circuitry may be similarly affected at FCS. The impact of the potential drift was evaluated, and it was determined that neither RPS nor the engineered safeguard circuitry may actuate at the required containment pressure of 5 psig. An evaluation determined that the actuation may not occur until slightly higher than the required pressure. Other systems are currently being evaluated to see if this same condition applies. The station is in MODE 5, refueling shutdown condition, and there is no immediate safety concern. The pressure instruments are located in the penetration area which is subject to elevated temperatures. The licensee notified the NRC Resident Inspector.
The condition was initially determined to be reportable under 10CFR50.72(b)(3)(ii)(B), plant in unanalyzed condition, based on a conservative assumption that the error introduced violated not only the Technical Specification limit (5.0 psig) but also the safety analysis limit of 5.4 psig, USAR Table 14.1-1. Subsequent evaluation of actual data concluded that the safety analysis limit was not exceeded and therefore not reportable under 10 CFR 50.72(b)(3)(ii)(B). LER 2012-004-1 reported this condition under 10CFR50.73(a)(2)(i)(B), 10CFR50.73(a)(2)(ix)(A), and 10CFR50.73(a)(2)(v)(A,B,C,D). Revision 2 of the LER will correct the reporting criteria. The NRC Resident Inspector was notified by the licensee. Notified the R4DO (Pick). |
| Where | |
|---|---|
Fort Calhoun  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000285/LER-2012-004 Re Inadequate Analysis of Drift Affects Safety Related Equipment |
| Time - Person (Reporting Time:+2.12 h0.0883 days <br />0.0126 weeks <br />0.0029 months <br />) | |
| Opened: | Nathan Seid 19:02 May 2, 2012 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Oct 19, 2012 |
| 47892 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Refueling Shutdown (0 %) |
| After | Refueling Shutdown (0 %) |
WEEKMONTHYEARENS 522012016-08-25T20:23:00025 August 2016 20:23:00
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