ENS 43359
ENS Event | |
|---|---|
20:00 May 11, 2007 | |
| Title | Bulletin 91-01 Loss of Double Contingency |
| Event Description | During the quarterly shutdown and clean-out of a rotary press used for pressing UO2-Gd203 powder in FMO, it was observed that approximately half of the schedule 80, one-inch diameter Chlorinated Poly Vinyl Chloride (CPVC) tubes placed in the lower shaft casing of the press did not extend the full length of the cavity as required by the nuclear safety analysis. These tubes are credited as a fixed neutron poison inside the casing and must extend the entire length of the cavity in order for the unit to be demonstrated safe geometry for [LEU] enriched UO2 under optimal moderation conditions. The independent control on mass remained intact, thus no unsafe condition existed. The as-found condition was analyzed and demonstrated to be safe.
The unit was in a shutdown condition and contained no Uranium at the time of the discovery. While this did not result in an unsafe condition, this event is being reported pursuant to NRC Bulletin 91-01 within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of discovery. NUMBER AND TYPES OF CONTROLS NECESSARY UNDER NORMAL OPERATING CONDITIONS The basis of criticality safety relies on geometry and mass as independent criticality safety controls. NUMBER AND TYPES OF CONTROLS WHICH FUNCTIONED PROPERLY UNDER UPSET CONDITIONS Mass control remained intact, thus no unsafe condition existed. NUMBER AND TYPES OF CONTROLS NECESSARY TO RESTORE A SAFE SITUATION Control on geometry demonstrated by current analysis. No uranium present at time of discovery. SAFETY SIGNIFICANCE OF EVENTS Low Safety Significance - independent control on mass remained intact - additional failure modes required before a criticality accident could occur. The as-found condition was analyzed and demonstrated to be safe. SAFETY EQUIPMENT STATUS Unit was shutdown for maintenance and will remain Shutdown until CPVC tube error corrected. STATUS OF CORRECTIVE ACTIONS Unit will remain shutdown pending final investigation results and implementation of additional preventive actions. The licensee will be notifying the North Carolina Radiation Protection Agency and the New Hanover County Emergency Management Agency. |
| Where | |
|---|---|
| Global Nuclear Fuel - Americas Wilmington, North Carolina (NRC Region 2) | |
| License number: | SNM-1097 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+16.12 h0.672 days <br />0.096 weeks <br />0.0221 months <br />) | |
| Opened: | Phillip Ollis 12:07 May 12, 2007 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | May 12, 2007 |
| 43359 - NRC Website
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Global Nuclear Fuel with Response | |
WEEKMONTHYEARENS 438972008-01-12T05:00:00012 January 2008 05:00:00
[Table view]Response Bulletin 91-01 Loss of Double Contingency Criticality Safety Controls ENS 433592007-05-11T20:00:00011 May 2007 20:00:00 Response Bulletin 91-01 Loss of Double Contingency ENS 422922006-01-27T20:00:00027 January 2006 20:00:00 Response 24 Hr Nrc Bulletin 91-01 Due to Criticality Controls Degradation ENS 403362003-11-18T20:55:00018 November 2003 20:55:00 Response 24 Hr Nrc Bulletin 91-01 Due to Criticality Controls Degradation 2008-01-12T05:00:00 | |