ENS 47509
ENS Event | |
|---|---|
20:58 Dec 7, 2011 | |
| Title | Reactor Building Ventilation Differential Pressure Above Technical Specifications |
| Event Description | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C) and (D), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and mitigate the consequences of an accident. Following initial troubleshooting of the reactor building ventilation (VR) differential pressure (DP) control loop, the Unit 1 VR DP controller was left in manual per the troubleshooting steps. It was noted at 1458 CST, on 12/7/11, that building DP was above the TS SR 3.6.4.1.1 required value of -0.25" H20. This rendered the secondary containment inoperable. Reactor building DP was returned to within the TS requirements within 14 minutes, and following system walkdowns, secondary containment was declared operable at 1615 [CST, on] 12/7/11. Troubleshooting will continue with other excursions above -0.25" H2O possible until repairs are complete (anticipated being complete week of 12/12/11).
This condition requires the licensee to comply with technical specifications values within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The licensee has notified the NRC Resident Inspector.
On December 7, 2011, following initial troubleshooting of the reactor building ventilation (VR) differential pressure (DP) control loop, the building DP was above the TS SR 3.6.4.1.1 value of -0.25 inch of vacuum water gauge. The secondary containment was declared inoperable and determined to be a loss of safety function. During the investigation it was determined that the event occurred due to a failure in the non-safety reactor building ventilation differential pressure control loop. The safety related function of the secondary containment and the non-safely reactor building ventilation differential pressure control loop are completely independent from one another. It is recognized that reactor building DP may exceed the TS SR [Technical Specification Surveillance Requirement] 3.6.4.1.1 value due to non-safety related component failures such as system fan trips, pressure controller malfunctions, rapid air temperature changes due to blast heater trips, or station heat recovery coil issues. A failure of a non-safety component does not result in a loss of safety function. The safely function of the secondary containment is maintained by adequate leak tightness and the operable ventilation equipment required to maintain the negative pressure requirements of TS SR 3.6.4.1.1. The safety related Stand-By Gas Treatment (SGT) ventilation system performs the negative pressure safety function. The secondary containment isolation safety function, isolation dampers and SGT systems remained operable throughout the event. Therefore this event did not constitute a loss of safety function of secondary containment and this event is not reportable. The licensee notified the NRC Resident Inspector. Notified R3DO (Pelke). |
| Where | |
|---|---|
LaSalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-0.3 h-0.0125 days <br />-0.00179 weeks <br />-4.1094e-4 months <br />) | |
| Opened: | Alan Mclaughlin 20:40 Dec 7, 2011 |
| NRC Officer: | John Knoke |
| Last Updated: | Dec 22, 2011 |
| 47509 - NRC Website
Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cb\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003E\u003Ca class=\"mw-selflink selflink\"\u003EENS 47509\u003C/a\u003E - \u003Ca href=\"/LaSalle\" title=\"LaSalle\"\u003ELaSalle\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E\u003C/b\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EReactor Building Ventilation Differential Pressure Above Technical Specifications\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 47509 - LaSalle\n","link":"","lat":41.24573888888889,"lon":-88.66919444444444,"icon":"/w/images/b/be/Constellation_icon.png"}],"imageoverlays":null} | |
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 %) |