ENS 47258
ENS Event | |
|---|---|
00:45 Sep 13, 2011 | |
| Title | Control Room Envelope Declared Inoperable |
| Event Description | On September 12, 2011, at 1745 PDT operators declared the control room envelope (CRE) inoperable and entered Technical Specification (TS) 3.7.10 Action B. This was due to discovery of inadequately documented CRE in-leakage test data.
On September 12, 2011, DCPP [Diablo Canyon Power Plant] personnel reviewing the CRE testing dated February 3, 2005 determined that the test report provided inadequate information to conclude that the most limiting alignment for control room pressurization would result in zero cubic feet per minute (CFM) in-leakage into the CRE, contrary to the Final Safety Analysis Report (FSAR) accident analysis for the most limiting design basis accident. Three of the four ventilation alignments tested had reported values of in-leakage greater than zero CFM. Plant staff implemented compensatory measures by placing the control room ventilation system into its pressurization accident alignment at 1828 PDT using the alignment from the test which had a reported value of zero CFM in-leakage. Additionally, administrative controls are being established to maintain post-Loss of Coolant Accident Emergency Core Cooling System leakage at a rate that would ensure operator doses are maintained less than the FSAR accident analysis results for the highest in-leakage rate reported by the test. Plant personnel notified the NRC Resident Inspector.
On 9/13/11 procedure revisions were approved with reduced limits for post-Loss of Coolant Accident Emergency Core Cooling System (ECCS) leakage. These reduced limits ensure operator doses are maintained less than the FSAR accident analysis results for the highest in-leakage rate reported by the CRE in-leakage test. Plant staff have since determined that the potential benefit of operating the control room ventilation system in its pressurization alignment was unnecessary with the ECCS leakage restriction and on 9/16/11 operators restored the control room ventilation system into its normal operating alignment. The licensee has notified the NRC Resident Inspector. Notified R4DO (Greg Pick)
This is an update to EN#47258 reported on 9/13/11 where it was reported that operators had declared the Control Room Envelope inoperable. [This report was subsequently] updated on 9/16/2011. On 10/18/11 at 16:45 PDT, plant staff determined that the CRE testing dated February 3, 2005 was not performed using a bounding configuration which would result in greatest consequence to the control room operators. The recorded in-leakage from the test was therefore considered to be non-bounding. [As a result of this determination, plant staff have] implemented additional compensatory measures by issuing a shift order requiring the use of self-contained breathing apparatus and potassium iodide tablets under certain accident conditions in accordance with Regulatory Guide 1.196 and NEI 99-03. Plant personnel notified the NRC Resident Inspector. Notified R4DO (Campbell). |
| Where | |
|---|---|
Diablo Canyon  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+1.2 h0.05 days <br />0.00714 weeks <br />0.00164 months <br />) | |
| Opened: | Bob Kline 01:57 Sep 13, 2011 |
| NRC Officer: | Charles Teal |
| Last Updated: | Oct 19, 2011 |
| 47258 - NRC Website
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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
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Both Trains of Containment Spray Removed from Service ENS 522602016-09-21T03:47:00021 September 2016 03:47:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Steam Line Pipe Whip Restraint Coupling Sleeve Found Not Engaged ENS 503342014-08-01T00:29:0001 August 2014 00:29:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Unanalyzed Condition ENS 498792014-03-06T17:06:0006 March 2014 17:06:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Regarding Potential Tornado Missile Damage to Emergency Diesel Exhaust Plenum ENS 496632013-12-19T15:52:00019 December 2013 15:52:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Two of Three Emergencey Diesel Generators Inoperable at the Same Time ENS 496342013-12-14T23:03:00014 December 2013 23:03:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Affecting Unit 1 Emergency Diesel Generator ENS 491482013-06-26T04:58:00026 June 2013 04:58:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Plant Shutdown Required Due to Rhr System Socket Weld Leak ENS 491472013-06-24T23:15:00024 June 2013 23:15:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Emergency Diesel Generators Unavailable for Auto-Start ENS 487262013-02-06T23:24:0006 February 2013 23:24:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition for Control Room Ventilation ENS 483952012-10-04T01:15:0004 October 2012 01:15:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Fire Protection Deficiencies ENS 482462012-08-29T00:00:00029 August 2012 00:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Mitigating Actions Implemented for Inoperable Control Room Envelope ENS 475642011-12-31T10:00:00031 December 2011 10:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Fire Barrier Rating of Vital Swtichgear Walls May Not Meet Standards ENS 474142011-11-03T22:50:0003 November 2011 22:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Control Room Ventilation Single Point Vulnerability ENS 472582011-09-13T00:45:00013 September 2011 00:45:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Control Room Envelope Declared Inoperable ENS 472232011-08-30T00:24:00030 August 2011 00:24:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Maintenance Inadvertently Renders Control Room Ventilation System Inoperable ENS 465312011-01-10T21:21:00010 January 2011 21:21:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Both Trains of Auxiliary Building Ventilation Became Inoperable ENS 457542010-03-10T03:16:00010 March 2010 03:16:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Loss of 1E Pumps Due to Degraded Voltage During Postulated Accidents ENS 454612009-10-23T15:00:00023 October 2009 15:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Post Loca Recirculation Valve Position Interlocks ENS 449272009-03-22T20:34:00022 March 2009 20:34:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unit 1 Steam Generator Found in an Unanalyzed Condition Related to Gaps on Seismic Washer Plates 2019-11-30T19:00:00 | |