ENS 47483
ENS Event | |
|---|---|
15:30 Nov 28, 2011 | |
| Title | 24-Hour Report Concerning a Localized Loss of a Geometry Criticality Control Contingency |
| Event Description | At 0930 CST on 11-28-11, during annual inspection of the C-400/C-409 floor drains and sumps according to procedure CP4-CU-CH6021, a chemical operator identified that an eye wash drain was no longer properly sealed around the concrete base and would not prevent solutions from entering the drain if challenged. NCSA [Nuclear Criticality Safety Assessment] CHM-001 requires specific drains to be sealed to prevent the accumulation of fissile material in the unsafe geometry drain system. In violation of NCSA CHM-001, the poured concrete base surrounding the eye wash drain #147 in C-400 was discovered to be broken loose from the floor so that it could no longer provide a seal against spilled uranium solution getting into the drain system.
SAFETY SIGNIFICANCE OF EVENTS Although the concrete block has broken loose from the floor, only a small crack exists at the base of the concrete block which would present a torturous solution path to the drain. Therefore, a large release will be prevented from transporting a significant amount of solution to the drain system. While the Safety Related Item failed, no fissile material was released onto the C-400 building floor and no fissile material entered the drain system through this drain. POTENTIAL CRITICALITY PATHWAYS INVOLVED In order for a criticality to occur a release of greater than a safe mass of uranium onto the floor of C-400 would have to occur. A solution containing greater than a safe mass would then have to migrate to the drain, leak into the drain system, and accumulate in an unfavorable geometry. CONTROLLED PARAMETERS The two process conditions relied upon for double contingency for this scenario are mass and geometry. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL Process is designed to handle uranium contaminated solutions with a maximum assay of 5.5 wt.% U235. NUCLEAR CRITICALITY SAFETY CONTROL AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES The first leg of double contingency is based on the mass of uranium in solution form that leaks out of the system. The analysis credits both the integrity of the system and the fact that the tanks and piping are inspected for leakage. Small leaks will be identified and fixed before they have leaked enough uranium mass in solution to be a concern. Since no leakage has occurred, this control was not violated. The second leg of double contingency relies on the integrity of the floor drain seals to prevent uranium solution from getting into the unsafe geometry drain system. Since a pathway from the floor to the drain system exists, this control was violated and the parameter was not maintained. Because the parameter was not maintained double contingency was not maintained. Double contingency was not maintained because the geometry parameter was not maintained. CORRECTIVE ACTIONS 1. Stop fissile solution operations in the vicinity of the eyewash drain. This was completed at 1000 CST on 11-28-11. 2. Restore the seal to this drain. Pending 3. Upon successful restoration of the seal for the eyewash drain #147, fissile solution operations may be resumed. Pending 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 Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-11-3171 and PGDP Event Report No. PAD-2011-20. |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 2) | |
| License number: | GDP-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+3.7 h0.154 days <br />0.022 weeks <br />0.00507 months <br />) | |
| Opened: | Billy Wallace 19:12 Nov 28, 2011 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Nov 28, 2011 |
| 47483 - 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 | |