ENS 47223
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ENS Event | |
|---|---|
00:24 Aug 30, 2011 | |
| Title | Maintenance Inadvertently Renders Control Room Ventilation System Inoperable |
| Event Description | On August 29, 2011, at 1724 PDT, plant operators discovered that the Control Room Envelope (CRE) boundary required by Technical Specification (TS) 3.7.10, 'Control Room Ventilation System (CRVS),' lost its integrity. This was due to maintenance personnel removing a blank flange on the line to Unit 2 CRVS dampers MOD-2 and MOD-2A with the dampers inoperable.
On August 29, 2011, at approximately 1400 PDT, plant personnel completed maintenance on Unit 2 control room dampers MOD-2 and MOD-2A and planned to perform static testing of the CRE on the morning of August 30, 2011. Prior to reporting off the clearance, maintenance personnel removed a blank flange from the upstream side of the dampers. This blank flange was maintaining the integrity of the CRE boundary while dampers MOD-2 and MOD-2A were inoperable during the maintenance. Upon completion of maintenance on the dampers, the blank flange was removed with shift foreman authorization. Later, personnel recognized that the flange had been removed prematurely while dampers MOD-2 and MOD-2A were still inoperable. Personnel took required actions associated with TS 3.7.10 and re-installed the blank flange on August 30, 2011, at 0110 PDT. The loss of the CRE boundary rendered the CRVS incapable of performing its specified safety function of mitigating the exposure of control room personnel to the consequences of an accident. The cause of the event was inadequate coordination between maintenance personnel and plant operators to maintain the integrity of the CRE boundary. Plant personnel notified the NRC Resident Inspector. |
| Where | |
|---|---|
Diablo Canyon  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+16.67 h0.695 days <br />0.0992 weeks <br />0.0228 months <br />) | |
| Opened: | Glenn Goelzer 17:04 Aug 30, 2011 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Aug 30, 2011 |
| 47223 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 544172019-11-30T19:00:00030 November 2019 19:00:00
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