ENS 49335
ENS Event | |
|---|---|
19:00 Sep 9, 2013 | |
| Title | High Energy Line Break Barrier Improperly Obstructed |
| Event Description | At 1400 [CDT] on September 9, 2013, plant personnel found HELB barrier HATCH-1/TB blocked. The hatch is diamond plate steel located on the turbine floor. Pallets, a fan and a gantry were positioned on top of the hatch possibly preventing pressure relief during a HELB event. This issue is being reported as an unanalyzed condition per 10CFR50.72(b)(3)(ii)(B). All items were removed from the hatch by 1800 on September 9, 2013.
The licensee notified the NRC Resident Inspector.
The licensee reviewed the design basis calculations and analyses for HELB events in the area where Hatch-1/TB is located. The review determined that it is acceptable to block or hold Hatch-1/TB down and that the painted markings on the hatch are overly restrictive. In looking at HELB calculation of record, feed water break at the feed water pumps, there is no flow path modeled between the HELB volumes. Therefore, if Hatch-1/TB is blocked, the physical flow path is in accordance with the Gothic model of the HELB volume. Further, the analyses also indicated that no credit is taken for the hatch to relieve as no HELBs are postulated in the room under the hatch. Finally, Hatch 1/TB structural integrity was verified assuming a HELB occurred with the hatch blocked as described in notification 49335 (pallets, fan and gantry) the barrier would function as designed. Licensee initiated a Work Request to remove any markings on Hatch-l/TB that indicate do not block or hold down. The licensee will notify the NRC Resident Inspector. The Region 3 Duty Officer (Valos) was notified. |
| Where | |
|---|---|
Monticello  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+3.65 h0.152 days <br />0.0217 weeks <br />0.005 months <br />) | |
| Opened: | Ronald Blenker 22:39 Sep 9, 2013 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Oct 4, 2013 |
| 49335 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (99 %) |
| After | Power Operation (99 %) |