ENS 47483: Difference between revisions

v t e 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.

ENS 47483 +/-
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
v • d • e

v t e Emergency Notification System
Paducah Gaseous Diffusion Plant with Response
WEEKMONTHYEAR2012-05-08T21:16:00 [Table view]
[ENS list for Paducah Gaseous Diffusion Plant]

@@ Line 16: / Line 16: @@
 | event date = 11/28/2011 09:30 CST
 | last update date = 11/28/2011
-| title = 24-Hour Report Concerning A Localized Loss Of A Geometry Criticality Control Contingency
+| title = 24-Hour Report Concerning a Localized Loss of a Geometry Criticality Control Contingency
 | event text = 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

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