ENS 48367
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ENS Event | |
|---|---|
04:10 Oct 3, 2012 | |
| Title | Unanalyzed Condition Due to High Energy Line Break Barrier Being Partially Open |
| Event Description | At 0010 [EDT] on 10/3/12, it was determined that an unanalyzed condition existed for the switchgear rooms on Unit 1. A degraded condition of a high energy line break (HELB) barrier was created during security surveillance. A HELB barrier door for the 27' elevation switchgear room was partially opened for a 14 minute period and could have allowed steam from a HELB on the 27' elevation of the Turbine Building to potentially impact equipment in both the 27' and 45' elevation switchgear rooms because these rooms are connected by a common ventilation system. The switchgear rooms are not analyzed for a steam environment. The degree of the impact could not be readily determined, but could likely affect the safety related equipment in the switchgear rooms. At 0024 [EDT] on 10/3/12, the HELB barrier door for the 27' elevation switchgear room was closed and the barrier restored which eliminated the potential unanalyzed condition. An 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report to the NRC is required under 10 CFR 50.72(b)(3)(ii)(B), 'Any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety' since there was not a reasonable expectation that the switchgear room environment could support operation of safety related equipment with the 27' elevation switchgear room door partially open. Further analysis is underway.
The licensee has notified the NRC Resident Inspector.
Subsequent engineering analysis conducted for this condition demonstrated that having the roll-up door stuck open six inches would not, should a HELB occur in the vicinity of the 27' switchgear room roll-up door, result in conditions within both switchgear rooms that would challenge the design limits and which would render the Class 1E electrical busses inoperable. Therefore the unit was not in a degraded or unanalyzed condition. As a result this condition is not reportable under 50.72(b)(3)(ii)(B). Based on this information, Calvert Cliffs is retracting notification message EN #48367. The licensee has notified the NRC Resident Inspector. Notified R1DO (Dwyer). |
| Where | |
|---|---|
Calvert Cliffs  Maryland (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+3.25 h0.135 days <br />0.0193 weeks <br />0.00445 months <br />) | |
| Opened: | Joseph Gioffre 07:25 Oct 3, 2012 |
| NRC Officer: | Dong Park |
| Last Updated: | Nov 19, 2012 |
| 48367 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 536632018-10-11T04:00:00011 October 2018 04:00:00
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