ENS 42732
ENS Event | |
|---|---|
02:00 Jul 27, 2006 | |
| Title | Limiting Condition for Operation 3.7.4 Deemed to Be Nonconservative |
| Event Description | The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73.
Palo Verde Nuclear Generating Station Technical Specification Limiting Condition for Operation (LCO) 3.7.4 requires only one of two atmospheric dump valves (ADV) per steam generator (SG) to be operable. Palo Verde Unit 3 currently has one ADV inoperable on the #2 SG. All other ADVs in Unit 3 (and all ADVs in Units 1 and 2) are OPERABLE. On July 26, 2006 at approximately 19:00 MST, Palo Verde Engineering personnel determined that this LCO is nonconservative since it does not satisfy the single failure criterion for the safety analyses for the accidents that would render one SG inoperable, specifically steam generator tube rupture (SGTR) with loss of offsite power (LOOP) which utilizes both ADVs on the unaffected SG. In case of one SG inoperable due to the event, and single failure of one ADV fail to open, the plant cannot be brought to safe shutdown condition during those accidents and may result in exceeding the acceptance criteria. This LCO should have required two ADVs per SG to be operable in order to satisfy safety analysis assumptions. An administrative control in accordance with NUREG-1432, Standard Technical Specifications will be put in place for immediate compensatory action. NUREG-1432 LCO 3.7.4 Condition A, one required ADV line inoperable requires restoration of the ADV line to OPERABLE status within 7 days. Reperformance of the safety analyses is expected to be the long term solution. The event did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. The event did not adversely affect the safe operation of the plant or health and safety of the public. The licensee notified the NRC Resident Inspector.
The notification is being retracted due to further evaluation by engineering and licensing personnel which has determined that the license basis for Palo Verde Nuclear Generating Station is bounded by a steam generator tube rupture with a stuck open ADV coincident with a loss of offsite power event. The safety analysis for this event relies on one ADV on the unaffected SG which, along with the stuck open ADV on the affected SG, limits the offsite dose consequences to within 10 CFR Part 100 guidelines. The safety analysis referred to in the initial ENS notification utilizes 2 ADVs on the intact SG to limit radiological doses to 10 per cent of Part 100 guidelines. However, as noted above, this analysis is not the bounding safety analysis for the SG tube rupture event. The administrative control identified in the initial notification will remain in effect until engineering and licensing personnel determine if a Technical Specification change is required to support ADV single failure criteria. The Resident Inspector has been notified of this retraction. Notified the R4DO (Cain). |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+1.12 h0.0467 days <br />0.00667 weeks <br />0.00153 months <br />) | |
| Opened: | David Oakes 03:07 Jul 27, 2006 |
| NRC Officer: | John Knoke |
| Last Updated: | Aug 29, 2006 |
| 42732 - NRC Website | |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 539682019-04-01T03:06:0001 April 2019 03:06:00
[Table view]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 Due to Eccs Leakage ENS 520832016-07-12T20:00:00012 July 2016 20:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Degraded Fire Barrier ENS 494112013-10-04T16:46:0004 October 2013 16:46:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Fire Event Could Result in a Hot Short That Could Adversely Impact Safe Shutdown Equipment ENS 488142013-03-09T02:21:0009 March 2013 02:21:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Spent Fuel Pool Criticality Analysis of Record Not Revised Following Power Uprate ENS 474592011-11-19T15:28:00019 November 2011 15:28:00 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 the Low Pressure Safety Injection System Was Subjected to High Pressure Resulting in Both Trains Being Declared Inoperable ENS 448462009-02-11T20:18:00011 February 2009 20:18:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Possibly Inadequate Backup Nitrogen Supply for Atmospheric Dump Operation ENS 431402007-02-03T19:32:0003 February 2007 19:32:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Technical Specification 3.0.3 Entered During Routine Surveillance Testing of Control Element Assemblies (Cea'S) ENS 428472006-09-19T08:05:00019 September 2006 08:05:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Pressurizer Heater Capacity Less than Tech Spec Limit ENS 427322006-07-27T02:00:00027 July 2006 02:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Limiting Condition for Operation 3.7.4 Deemed to Be Nonconservative ENS 420502005-10-11T23:02:00011 October 2005 23:02:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 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 Tech Spec Required Shutdown of Both Unit 2 and 3 ENS 417892005-06-23T15:23:00023 June 2005 15:23:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unit 2 Aux Feedwater Train Separation Not Maintained During Operation 2019-04-01T03:06:00 | |