ENS 44846
ENS Event | |
|---|---|
20:18 Feb 11, 2009 | |
| Title | Possibly Inadequate Backup Nitrogen Supply for Atmospheric Dump Operation |
| 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 of under the reporting requirements of 10 CFR 50.73.
Palo Verde Nuclear Station declared all three Unit's atmospheric dump valves (ADV) inoperable at 1318 MST. The reason for the inoperability is the discovery by engineering personnel that the ADV backup nitrogen capacity, required to operate the valves to mitigate certain accident scenarios, was not adequate. There are 4 ADVs (one on each steam line with two steam lines per steam generator) for each of the three units. Engineering review of a loss of offsite power event determined that the current nitrogen supply of 13.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> will not be adequate to get the plant to shutdown cooling entry conditions during a natural circulation asymmetric cooldown (i.e. Feedwater Line Break, Main Steam Line Break, and Steam Generator Tube Rupture). Actions are in progress to restore the operability of the ADVs. If unsuccessful, all three units will be required by the Technical Specifications to be in Mode 3, Hot Shutdown, by 1918 MST on February 12, 2009. The licensee notified the NRC Resident Inspector.
This is a retraction of the condition reported in EN 44846 on February 11, 2009 at 19:31 EST. Upon further review of the condition, engineering personnel have determined that the ADV nitrogen supply was adequate to mitigate the consequences of the postulated events and the ADVs were declared operable at 04:30 MST on February 12, 2009. Therefore, no reportable condition existed. The licensee notified the NRC Resident Inspector. Notified R4DO (Miller). |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-0.78 h-0.0325 days <br />-0.00464 weeks <br />-0.00107 months <br />) | |
| Opened: | Tim Gaffney 19:31 Feb 11, 2009 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Feb 12, 2009 |
| 44846 - 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 %) |
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 | |