05000353/LER-2013-003
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3532013003R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 2 was in Operational Condition (OPCON) 1 (Power Operation) at 100% power. There were no other structures, systems or components out of service that contributed to this event.
Description of the Event
On Wednesday, October 30, 2013, Limerick Unit 2 was operating at 100% power. At 1550 hours0.0179 days <br />0.431 hours <br />0.00256 weeks <br />5.89775e-4 months <br />, the reactor enclosure low delta pressure alarm (EIIS:ALM) actuated and reactor enclosure pressure was observed recovering to a normal pressure of 0.33 inch of vacuum water gauge.
An investigation identified that a worker in the reactor enclosure (EIIS:NH) on the 313 foot elevation was using the equipment airlock when an opening of both airlock doors (EIIS:DR) occurred. The worker was exiting the reactor enclosure and entering the fan room using the airlock when the breach occurred. The worker did not effectively verify that the inboard door latch was engaged when the door was closed. The worker then opened the outboard door and the inboard door also opened due to the differential pressure on the door. Both doors were closed in less than 10 seconds and the breach of secondary containment was terminated. The worker notified Operations shift management of the unexpected containment breach.
Technical Specification (TS) 3.6.5.1.1 Reactor Enclosure Secondary Containment Integrity surveillance requirement 4.6.5.1.1.a requires verification that reactor enclosure pressure is greater than or equal to 0.25 inch of vacuum water gauge which is performed on a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> frequency. The TS surveillance requirement 4.6.5.1.1.b.2 requires at least one door in each access to the reactor enclosure be verified closed which is performed on a 31 day frequency. TS 3.6.5.1.1 is applicable in operational conditions (OPCON) 1, 2 and 3.
This LER is being submitted pursuant to the requirements of 10CPR50.73(a)(2)(v)(C) for a condition that could have prevented the fulfillment of the safety function of structures or systems needed to control the release of radioactive material.
Analysis of the Event
There was no actual safety consequence associated with this event.
The potential safety consequences of this event were minimal. Both RC FORM MA (10-2010)
Cause of the Event
The cause of the airlock breach is the reactor enclosure airlock design does not prevent both doors from being opened simultaneously.
A contributing cause was the airlock door self-closing feature failed to fully close and latch the airlock door and the worker did not properly verify the door was latched following use.
Corrective Action Completed The airlock door self-closing feature was functionally tested.
Corrective Action Planned A reactor enclosure airlock design change will be evaluated.
Previous Similar Occurrences Unit 2 LER 2013-002 was submitted due to a reactor enclosure airlock breach caused by a non-functional airlock door open indicating light not providing the correct door status. There have also been previous similar occurrences in the prior three years based on a review of the operator logs. The events were identified by an actuation of the airlock seal open alarm which indicates that both airlock doors were open for a period exceeding 10 seconds.
MC FORM 38M (10-2010)
NRCFORNMNA
(104010) U IL NUCLEAR REGULATORY CONNIISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
00CAET 1. FACIUT1NAME B. Lan mumein SEtitUEmATAAL REV Component Data Component Number Component Name Manufacturer Model Number Door-560 Reactor Enclosure Fan Room Door Woolley 7790 DWG/HW SET 13 hiRC FORM 386A (10-2010)