ENS 40700
ENS Event | |
|---|---|
13:45 Apr 23, 2004 | |
| Title | Criticality Control 24-Hour (Bulletin 91-01) Report |
| Event Description | The following information was obtained from the regulatee via facsimile:
At 0845, on 04-23-04, the Plant Shift Superintendent was notified of a violation of Nuclear Criticality Safety (NCS) controls associated with storage of waste drums in the C-335 building. Two Spacing Exempt waste drums were identified to have been characterized utilizing erroneous results from the Q2 drum monitor in violation of Nuclear Criticality Safety Evaluation (NCSE) 091. The characterization is based on it being unlikely that the drum monitor will give an erroneous result. The purpose of the requirements is to ensure the mass in an NCS Spacing Exempt waste drum is below the [DELETED] 235U limit. The waste drums have been independently sampled and demonstrated to be below the [DELETED] 235U limit. The NRC Resident Inspector has been notified of this event. SAFETY SIGNIFICANCE OF EVENTS: While the [DELETED] 235U limit was not exceeded for these two drums, both legs of double contingency were lost and the potential exists for waste drums to be non-conservatively characterized using the Q2 drum monitor. POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO(S)) OF HOW CRITICALITY COULD OCCUR: In order for a criticality to occur, two or more waste drums containing above the [DELETED] 235U limit would have to be accumulated to exceed a critical mass with no spacing and be moderated. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.): Double contingency is maintained by implementing two controls on mass. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS): Each drum contains less than [DELETED] 235U at an enrichment of less than 1.5 wt% 235U. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES: The first leg of double contingency relies on it being unlikely for the Q2 drum monitor to provide an erroneous result. The drum monitor measurement gave a non-conservative erroneous result, which was used to characterize the drum. Therefore, the unlikely statement was violated. However, the drums were subsequently sampled with the result being below the [DELETED] 235U limit for each drum. Therefore, the parameter was maintained. The second leg of double contingency relies on it being independently unlikely for the Q2 drum monitor to provide an erroneous result. The independent drum monitor measurement gave a non-conservative erroneous result, which was independently used to characterize the drum. Therefore, the independent unlikely statement was violated. However, the drums were subsequently independently sampled with the independent result being below the [DELETED] 235U limit for each drum. Therefore, the parameter was maintained. Although the parameter was maintained, double contingency is based on two controls on one parameter. Therefore, double contingency was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED: 1. Characterize waste drums (PF-04-7258 and PF-03-5051) using the independent sample results. Completed 04/23/04. 2. Complete the 'extent of condition' examination prior to making a determination for removal of the ropes and postings. The Q2 drum monitor requires a density of material input to properly characterize drum material. Sodium fluoride (NaF) density was used instead of uranyl fluoride (UO2F2) which resulted in a non-conservative characterization. The drum contained both materials. Plant personnel have imposed spacing requirements on all other drums in the immediate area that have questionable characterizations until they can be properly analyzed. To prevent re-occurrence, plant management has issued orders and mandates to verify drum contents utilizing two different and distinct sampling methods (i.e. monitoring and laboratory sampling). |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 2) | |
| License number: | GDP-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+15.02 h0.626 days <br />0.0894 weeks <br />0.0206 months <br />) | |
| Opened: | Steve Skaggs 04:46 Apr 24, 2004 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Apr 24, 2004 |
| 40700 - 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 | |