ENS 46592
ENS Event | |
|---|---|
15:30 Feb 3, 2011 | |
| Title | 24 Hour Notification Under Bulletin 91-01 Concerning Leakage of Moderating Liquid |
| Event Description | At 0930 CST on 02-03-11, the Plant Shift Superintendent (PSS) was notified that a steam condensate line broke above the C-310 withdrawal room and water leaked through the ceiling into the withdrawal room on the ground floor. Water accumulated greater than 0.5 inch in depth in the diked area above the withdrawal room in violation of NCSA [Nuclear Criticality Safety Approval] 310-004. NCSA 310-004 requires that open containers with volumes greater than 5.5 gallons shall not contain pre-existing moderator greater than 0.5 inches in depth. During the walk down, it was discovered that the sprinkler heads currently installed above the withdrawal room are rated at 160F in violation of the NCS [Nuclear Criticality Safety] limit. NCSE [Nuclear Criticality Safety Evaluation] 032 requires the minimum activation temperature to be no lower than 200F. The sprinkler system was taken out of service and drained at 2131 CST on 02-03-11 and the level of water accumulated in the diked area was verified to be less than 0.5 inches at 0426 CST on 02-04-11.
Since one leg of double contingency was lost, this is being reported to the NRC as a 24-hour Event Report in accordance with NRC BL 91-01 Supplement 1. The NRC Senior Resident Inspector has been notified of this event. SAFETY SIGNIFICANCE OF EVENTS The first leg of double contingency is based on preventing a release of fissile material greater than the safe mass of uranium. This event did not release fissile material greater than the safe mass of uranium. POTENTIAL CRITICALITY PATHWAYS (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR) In order for a criticality to be possible, a large UF6 release containing greater than a critical mass of uranium would have to occur and accumulate greater than the critical configuration. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.) The two process conditions relied upon for double contingency are mass and geometry. ESTIMATED AMOUNT, ENRICHMENT, FORM OF MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS) Product withdrawal assay at the time of the event was less than 4.95 wt% U235. However, no UF6 release occurred. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES The first leg of double contingency is based on preventing a release of fissile material greater than the safe mass of uranium. Since a UF6 release containing greater than the safe mass has not occurred, the mass parameter has maintained. The second leg of double contingency limiting moderating liquids in open containers to less than 0.5 inches and requiring the sprinkler head activation temperature to greater than 200F. Since the diked area above the withdrawal room did accumulate water level greater than 0.5 inches, the control was violated. Additionally, since the installed sprinkler heads activation temperature is less than 200F, a design feature of NCSE 032 was violated. Therefore, double contingency was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED Shiftly checks of the diked area above the withdrawal have been initiated to ensure water level is not accumulating. The condensate leak above the withdrawal room was repaired and solution level verified to be less than 0.5 inches (0426 [CST] on 2/4/11). The sprinkler systems associated with the sprinkler heads above the withdrawal room have been isolated until the sprinkler heads can be replaced with heads that comply with NCSE 032 (Systems isolated at 2131 [CST] on 2/3/11). |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 2) | |
| License number: | Gdp-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+17.58 h0.733 days <br />0.105 weeks <br />0.0241 months <br />) | |
| Opened: | Calvin Pittman 09:05 Feb 4, 2011 |
| NRC Officer: | Dong Park |
| Last Updated: | Feb 4, 2011 |
| 46592 - NRC Website | |
Paducah Gaseous Diffusion Plant with Response | |
WEEKMONTHYEARENS 483982012-10-10T18:05:00010 October 2012 18:05:00
[Table view]Response Double Contingency Control for Empty Cylinders Not Maintained ENS 479112012-05-08T21:16:0008 May 2012 21:16:00 10 CFR 76.120(c)(2), Response Autoclave High Pressure Isolation System Failure ENS 474832011-11-28T15:30:00028 November 2011 15:30:00 Response 24-Hour Report Concerning a Localized Loss of a Geometry Criticality Control Contingency ENS 473102011-09-30T13:54:00030 September 2011 13:54:00 Response 24-Hour Nrc Bulletin 91-01 Report Involving a Loss of One Leg of Double Contingency ENS 471762011-08-19T13:15:00019 August 2011 13:15:00 Response 24-Hr Loss of Criticality Control Report Required Under Bulletin 91-01, Supplement 1 ENS 465922011-02-03T15:30:0003 February 2011 15:30:00 Response 24 Hour Notification Under Bulletin 91-01 Concerning Leakage of Moderating Liquid ENS 463122010-10-06T16:06:0006 October 2010 16:06:00 Response 24 Hour Notification Under Bulletin 91-01 Concerning Cooldown Verification of Uf6 Cylinders ENS 461052010-07-17T19:07:00017 July 2010 19:07:00 Response 24 Hour 91-01 Bulletin Report on Loss of One of Two Criticality Control Contingencies ENS 454922009-11-12T17:15:00012 November 2009 17:15:00 Response Violation of a Nuclear Criticality Safety Control ENS 450422009-05-04T10:07:0004 May 2009 10:07:00 Response 24 Hour 91-01 Bulletin Report on Loss of One of Two Criticality Control Contingencies ENS 445582008-10-09T20:37:0009 October 2008 20:37:00 Response 24-Hours Bulletin 91-01 Report Involving Failure to Visually Inspect Storage Cylinders ENS 442232008-05-18T22:21:00018 May 2008 22:21:00 Response Violation of a Nuclear Criticality Safety Approval - 24-Hour Report ENS 441512008-04-17T21:44:00017 April 2008 21:44:00 Response 24-Hour Nrc Bulletin 91-01 Report Involving an Excessively Large Container Found in a Fissile Control Area ENS 441002008-03-26T19:57:00026 March 2008 19:57:00 Response 24 Hour Report of Degraded Criticality Control ENS 440562008-03-11T19:57:00011 March 2008 19:57:00 Response Two Cylinders Identified with Weight Change Prior to Wash ENS 432322006-09-23T03:00:00023 September 2006 03:00:00 Response Reported Under Nrc Bulletin 91-01 24 Hour Notification ENS 421652005-11-22T18:05:00022 November 2005 18:05:00 Response Improper Criticality Spacing for Waste Drum ENS 411582004-10-29T14:45:00029 October 2004 14:45:00 Response Criticality Control Report ENS 410202004-09-04T18:45:0004 September 2004 18:45:00 Response Violation of Nuclear Criticality Safety Control in the Process Building ENS 408732004-07-14T18:00:00014 July 2004 18:00:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 408602004-07-08T20:50:0008 July 2004 20:50:00 Response 24 Hour Nrc Bulletin 91-01 Loss of Criticality Control ENS 407232004-05-03T21:00:0003 May 2004 21:00:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 407002004-04-23T13:45:00023 April 2004 13:45:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 408052004-04-23T10:53:00023 April 2004 10:53:00 Response Paducah Gaseous Diffussion Plant - Response Bulletin 91-01 24 - Hour Report ENS 406412004-04-04T19:30:0004 April 2004 19:30:00 Response 24-Hour Nrc Bulletin 91-01 Loss of Criticality Control Notification ENS 404552004-01-16T21:27:00016 January 2004 21:27:00 Response 24 Hour Notification for Bulletin 91-01 Loss of Criticality Safety Controls Involving Waste Drum ENS 404472004-01-13T19:00:00013 January 2004 19:00:00 Response 24 Hour Notification for Bulletin 91-01 Loss of Criticality Safety Controls Involving Waste Drum ENS 403562003-11-25T09:45:00025 November 2003 09:45:00 Response 24 Hour Nrc Bulletin 91-01 Notification Regarding Loss of Double Contingency Protection ENS 401512003-09-11T13:45:00011 September 2003 13:45:00 Response Double Contingency Was Not Maintained for Non-Fissile Nams. ENS 401392003-09-07T12:50:0007 September 2003 12:50:00 Response Criticality Controls Degradation at Paducah ENS 401092003-08-27T14:00:00027 August 2003 14:00:00 Response Procedural Deficiency Omission 2012-05-08T21:16:00 | |