ENS 40139
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ENS Event | |
|---|---|
12:50 Sep 7, 2003 | |
| Title | Criticality Controls Degradation at Paducah |
| Event Description | At 0750 on 9/7/03, it was discovered that the Recirculating Cooling Water (RCW) Supply valve for C333 Unit 6 Cell 2 was not positioned correctly for the current condition of the cell, in violation of NCSA CAS-011. On 9/3/03, the cell was in a fluorinating environment with the Odd R-114 system drained and evacuated for leak repairs, Odd RCW valves closed, the Even R-114 system was not drained with the Even RCW valves open satisfying the conditions of CAS-002. It was determined that the cell needed to have a UF6 negative obtained for maintenance work. The UF6 negative was initiated without closing the Even RCW Supply valve, tagging both the Supply and Return valve, and without performing the independent checks for valve position, which violates NCSA CAS-002. Once the UF6 negative was obtained, the cell transitioned to NCSA CAS-011 without satisfying the RCW isolation controls of that NCSA. Both RCW isolation controls require that the RCW Supply valve be tagged closed and that the RCW Return valve be tagged open and both valves independently verified to be positioned correctly. The NRC Senior Resident Inspector has been notified of this event.
SAFETY SIGNIFICANCE OF EVENTS: Since the process condition (lack of moisture in the coolant, and therefore in the process gas system) was maintained, the safety significance of this incident is low. POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO OF NOW CRITICALITY OF HOW CRITICALITY COULD OCCUR): Once the fluorinating environment is removed from a process cell, moisture that may leak into the process gas system could potentially moderate any uranium that may be present. Sufficient water would have to leak into the process gas system and moderate a critical mass of uranium. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC Double contingency is maintained by implementing two controls on mass. 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 ensuring that a coolant condenser leak will not introduce RCW (moderator) into the process gas side of a cell through the coolant. This is accomplished by either maintaining a fluorinating environment in the cell or by restricting /isolating the RCW supply prior to removing the fluorinating environment. This restriction/isolation is accomplished by either removing a supply spool piece or closing and tagging the manual supply valve and tagging open the return valve. Neither of these two RCW alignments was maintained. The second leg of double contingency is based on an independent verification of the RCW alignment relied upon for the first leg of double contingency. The independent verification was not performed. Therefore, this control was lost, Since double contingency is based on two controls on one parameter, double contingency was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMPNTED: At 1010 on 9-7-03, the Even RCW Supply valve was tagged closed, the Odd RCW Return valve was tagged open, and both valves were independently verified. The coolant moisture content was checked and was less than minimum detectible moisture. These actions have placed the system back in compliance with NCSA CAS-011. |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 3) | |
| License number: | Gdp-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+10.42 h0.434 days <br />0.062 weeks <br />0.0143 months <br />) | |
| Opened: | Thomas White 23:15 Sep 7, 2003 |
| NRC Officer: | Rich Laura |
| Last Updated: | Sep 7, 2003 |
| 40139 - NRC Website
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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 | |
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