05000458/FIN-2011008-04
From kanterella
Jump to navigation
Jump to search
Finding | |
|---|---|
| Title | Station Blackout-Containment Venting |
| Description | The team reviewed Condition Report CR-RBS-2011-03471, concerning River Bend Station\\\'s severe accident management program associated with 4-hour station blackout coping duration issues. As documented in Condition Report CR-RBS2011- 03471, Abnormal Operating Procedure, AOP-0050, Station Blackout, provided instructions for venting pressurized containment vapor to the annulus through a 3-inch hardened vent path. However, the licensee\\\'s evaluation of these actions determined that the hardened vent path was too small to prevent containment over pressurization in an extended station blackout greater than the 4-hour coping period. It can delay but not prevent containment failure which is calculated to occur at 50-55 psia approximately 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> into an extended station blackout. Based on the licensee\\\'s analysis Calculation 813.18.12.4-030, the operator actions which specified venting containment through the containment/hydrogen purge ventilation system components have been deleted from Abnormal Operating Procedure, AOP-0050 and revised in Emergency Operating Procedure, EOP-0005 because of the potential personnel hazards. The licensee\\\'s revised station blackout coping strategy involves venting through one of the containment personnel airlocks and out to the environment through an open auxiliary building door. In order to support the revised venting through one of the containment personnel airlocks to the environment described in procedures AOP-0050 and EOP-0005, the licensee performed a 10 CFR 50.59 review for these procedures. Based on the results of this review, both of these procedural changes were screened out and a 10 CFR 50.59 evaluation was not performed. Calculation G13.18.12.4*4, Revision 0, evaluated the conditions in containment resulting from a station blackout of indefinite length with reactor core isolation cooling and high pressure core spray as the only available makeup sources. The team reviewed the respective cases described in this calculation and determined that several of these cases resulted in exceeding the heat capacity temperature limit prior to the 4-hour station blackout coping limit. Accordingly, containment venting currently described in procedures AOP-0050 and EOP-0005, through the containment air-lock would be initiated before the 4-hour coping time. Based on these reviews, the team determined that the licensing basis for containment and the associated systems including the containment personnel airlock described in the updated safety analysis report are to maintain containment integrity during and following a design basis accident. Additionally, the team determined that the use of the personnel airlock as a vent path to depressurize containment during a station blackout event did not appear to be described in any of the available licensing basis documents. Accordingly, the team views that the licensee\\\'s strategy of venting through one of the containment airlocks and out to the environment through an open auxiliary building door appears to represent an unreviewed safety question. The inspectors determined that more inspection is necessary to resolve the issue. Since more information is necessary, the issue is considered an unresolved item pending further NRC review. |
| Site: | River Bend  |
|---|---|
| Report | IR 05000458/2011008 Section 1R21 |
| Date counted | Dec 31, 2011 (2011Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | K Clayton G George T Farnholtz S Makor N Greca C Edwards J Braisted B Lattak Claytong George L Carson S Garchow J Melfi A Barrett G Larkin V Gaddy M Runyan R Latta C Alldredge |
| INPO aspect | |
| ' | |
Finding - River Bend - IR 05000458/2011008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Finding List (River Bend) @ 2011Q4
Self-Identified List (River Bend)
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||