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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.

The following information is provided without quotation for readability: DESCRIPTION: On 10/09/08 at 1537 hours it was determined that procedure CP4-CU-CH6430, "In Storage Fissile Cylinder Inspection", does not fully meet the periodic inspection requirements of NCSA GEN-003. GEN-003 requires inspection every four years of all thick wall cylinders that contained fissile material since they were last washed on the inside of the cylinder. Only cylinders that were filled with fissile material on their last fill have been identified for inspection. Cylinders filled with fissile material, emptied and subsequently filled with non-fissile material and emptied, have not been inspected as required. Approximately 73 Cylinders that have contained fissile material since their last washing have not been inspected in violation of the requirement of NCSA GEN-003, these cylinders could contain residual nonvolatile material referred to as heel. Potentially the residual heel could contain fissile material. Double contingency is maintained by implementing two independent controls on one parameter (moderation). The first leg of double contingency relies on the design of the cylinder to ensure moderation control. Cylinders are designed to the requirements of ANSI N14.1 and ensure that it is unlikely for the cylinder wall to breach and allow water intrusion. This control on moderation was not violated. The second leg of double contingency relied on inspections every 4 years of the cylinder wall, valve, and plug for abnormal corrosion. This control ensures that in the event of a cylinder breach, it is unlikely that sufficient moderation to cause a criticality will enter the cylinder before it is identified and mitigated. Since the cylinders were not inspected within the 4 year time frame as required, this control on moderation was violated. The NRC Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-08-2918; PGDP Event Report No. PAD-2008-31; NRC Worksheet No. 44558. SAFETY SIGNIFICANCE OF EVENTS: Although a control requiring inspection of the cylinders every 4 years was violated, no cylinder breaches occurred. Later inspections identified no cylinder integrity issues, moderation control was lost and double contingency was not maintained. POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR): In order for a criticality to be possible, more than 10kgs of water would have to enter a breach in a cylinder which contains more than a critical mass of material enriched to greater than 1.0 wt% 235U. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.): Moderation. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS) : There were 73 cylinders which were not inspected as required. These cylinders had at one time held fissile material. The cylinders were emptied except for a small residual heel and then filled with non-fissile material. The non-fissile material was then emptied leaving only the residual heel in the cylinder. Cylinder heels are typically less than 50 pounds. Assay is always less than 5.5% enrichment. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES: NCSA GEN-003 requires cylinders containing material enriched to greater than or equal to 1.0 wt % 235U to be inspected every 4 years to identify significant signs of degraded cylinder wall, valve and plug. These cylinders were filled with fissile material, emptied and then subsequently filled with non-fissile material and then emptied again, but were not inspected within the four year requirement. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED : Cylinders have been inspected per the CP4-CU-CH6430 and the identified cylinders were found to comply with NCSA GEN-003.

• * * UPDATE AT 1750 EDT ON 10/10/08 FROM BILLY WALLACE TO STEVE SANDIN VIA FAX * * *

On 10/10/08 at 1500 CDT, an additional 8 cylinders were discovered which had not been properly inspected. The additional cylinders were of a different size than the initial cylinders found, but fall under the same requirement. The additional cylinders have been inspected and all met the NCSA requirements. Notified R2DO (Shaeffer) and NMSS (McCartin).