ENS 41390
ENS Event | |
|---|---|
14:20 Feb 9, 2005 | |
| Title | Both Trains of the Control Structure Emergency Outside Air Supply System Inoperable |
| Event Description | At 09:20 am, on February 9th, the control room declared both trains of Control Structure Emergency Outside Air Supply System (CREOASS) inoperable. The control room was notified of an inoperable boundary door that was not closed and latched and therefore would not have allowed CREOASS to perform its safety function of maintaining the Control Structure at a positive pressure if required. The door was closed and locked [at 11:15] to restore the habitability boundary.
The door has since been repaired [adjustment of latch mechanism]. Initial investigation determined that the door had been unlocked at approximately 09:20 this morning by an elevator vendor to perform maintenance. This is being reported as an event or condition that could have prevented the fulfillment of the safety function required to mitigate the consequences of an accident. CREOASS was not called upon to function during the period that the door was not operable. The licensee notified the NRC Resident Inspector.
The following information was provided by the licensee (licensee text in quotes): On 2/9/2005, PPL Susquehanna LLC reported a loss of safety function for the Control Room Emergency Outside Air Supply System (CREOASS) based on one of the Control Structure Habitability boundary doors being found partially open. Positive air pressure generated by the Control Structure HVAC System prevented the door closure mechanism from maintaining the door closed. The door was closed to restore the habitability boundary. The event was reported as a condition that could have prevented the fulfillment of the safety function required to mitigate the consequences of an accident. The Safety Function of the CREOASS is to provide adequate radiation protection to permit occupancy of the Control Room under accident conditions for the duration of the accident. The CREOASS accomplishes this by: 1) filtering the outside make-up air supply and 2) maintaining a positive pressure in the control structure habitability boundary to limit unfiltered air in leakage into the boundary. A subsequent engineering evaluation concluded that with the door closure mechanism providing a resistive force, CREOASS would have been able to maintain a positive pressure within the boundary and perform its safety function as described above. In conclusion, the reported condition did not result in a loss of safety function under 10CFR50.72 (b)(3)(v)(D) and is therefore being retracted. The NRC Resident Inspector and R1DO (Noggle) have been notified. |
| Where | |
|---|---|
Susquehanna  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+0.03 h0.00125 days <br />1.785714e-4 weeks <br />4.1094e-5 months <br />) | |
| Opened: | Gordy Robinson 14:22 Feb 9, 2005 |
| NRC Officer: | Chauncey Gould |
| Last Updated: | Apr 8, 2005 |
| 41390 - 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 41390\u003C/a\u003E - \u003Ca href=\"/Susquehanna\" title=\"Susquehanna\"\u003ESusquehanna\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E\u003C/b\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EBoth Trains of the Control Structure Emergency Outside Air Supply System Inoperable\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 41390 - Susquehanna\n","link":"","lat":41.09256666666667,"lon":-76.14176944444445,"icon":"/w/images/c/c7/Talen_Energy_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 (91 %) |
| After | Power Operation (91 %) |