ENS 45492
ENS Event | |
|---|---|
17:15 Nov 12, 2009 | |
| Title | Violation of a Nuclear Criticality Safety Control |
| Event Description | At 1115 CST on 11/12/09, abandoned cell piping was reported in C-331 and C-335 cell housings. The 16-inch abandoned piping is from the cell recycle line that was replaced in the mid 1970s. NCS [Nuclear Criticality Safety] controls require that equipment openings with unknown uranium deposits shall be covered with water-proof covers that are fire resistant. Since the piping contains an unknown uranium mass, and was discovered without water-proof covers, the NCS control was violated.
Since moderation is the primary criticality control, and where double contingency cannot be re-established within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, this is being reported to the NRC as a 4-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-09-2781; PGDP Event Report No. PAD-2009-19. Safety significance of events: Although the NCS control to cover the pipe openings was violated, it was not exposed to a liquid moderator. The geometry of the pipe is safe for a maximum enrichment that may be in the pipe. During the plant modifications that replaced the cell recycle lines, the maximum plant enrichment was 2.0 wt. % U235. There are no indications, based on quarterly NDA scans, that the piping contains greater than a safe mass of uranium. Therefore, the safety significance of the event is low. Potential criticality pathways involved: The maximum plant enrichment at the time the piping was in operation was a maximum 2.0 wt. % U235. The piping is contained in housing without fire suppression. The single parameter pipe diameter for that enrichment is greater than 16 inches. In order for a criticality to be possible, the pipe would have to contain greater than a critical mass. A large amount of moderator would have to enter the horizontal pipe opening. Greater than a critical mass would then have to be washed from the pipe due to the unlikely moderator release at the pipe opening. The washed material would then have to accumulate in an unsafe geometry. Controlled parameters: Moderation. Estimated amount, enrichment, form of licensed material: The assay of any material is less than or equal to 2.00 wt. % U235. Nuclear Criticality safety control(s) or control systems(s) and description of the failures or deficiencies: The first leg of double contingency relies on control of moderation. Moderator intrusion associated with sprinkler activation is controlled by limiting fire sprinkler head activation temperatures at the ceiling and bypass heights. The analysis also determined that significant moderator intrusion into open fissile piping due to inadvertent spills, RCW/oil line leaks, or other mechanism is unlikely. These controls were not violated and an unlikely moderator release event has not occurred at the pipe opening. The second leg of double contingency is also based on moderation. Piping exceeding 10.25 inches that contains an unknown or greater than safe mass deposit is required to have openings covered with fire resistant waterproof covers. Since the piping is nominal 16 inches in diameter, contains an unknown uranium mass, the NCS control was violated. Since the openings are not covered resulting in a loss of NCS control and there are two controls on one parameter, the process condition was not maintained. Corrective actions to restore safety systems and when each was implemented: Control access to the area. Exempt the pipe from NCS controls based on enrichment determination, cover the pipe openings, or quantify the uranium mass in the pipe. |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 2) | |
| License number: | GDP-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+-1.1 h-0.0458 days <br />-0.00655 weeks <br />-0.00151 months <br />) | |
| Opened: | Robert Maglasang 16:09 Nov 12, 2009 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Nov 12, 2009 |
| 45492 - 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 | |