Event Notification Report for May 18, 2001

This licensee is authorized for the receipt, possession, processing, storage, handling and shipment of radioactive waste resins. During routine operations at the facility, a spill of approximately four cubic feet occurred from one of the process vessels. The vessel was shut down and the facility evacuated. It is estimated that 29 millicuries of activation and mixed fission products were released during the spill. The material was released into a controlled area. There were no environmental releases. Negative pressure was maintained during the event. The HVAC system was shut down after the release as was the thermal system to the process vessel. During the investigation, five individuals were slightly contaminated as confirmed by nasal swipes. Invivo counting of these individuals will be conducted on Wednesday, May 23 at Oak Ridge National Laboratory. Temperatures in the area have now decreased enough for personnel to enter and make a physical evaluation. Video cameras recorded the event and it is believed at this time that the vessel was overpressurized. A complete investigation and root cause analysis will be performed by the licensee to determine the cause of the event.

4 HOUR 91-01 BULLETIN

During normal operations, a concern was identified of a potential fissile material operation in equipment that had been previously identified as an operation that contained material <1 % U-235. Upon investigation of the concern Nuclear Criticality Safety Personnel identified an unanalyzed condition in the X-330/333 "A" booster. Based on the identified condition this is a 4 hour reportable event. Currently the equipment is isolated. A sample shows the equipment contains material at <1% U-235.

SAFETY SIGNIFICANCE OF EVENTS:

LOW. the equipment is shutdown and has a pressure of 0.8 psia. The maximum mass in the X-330 to X-333 "A" compressor at this pressure is 41 gram U-235

POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO[S] OF HOW CRITICALITY COULD OCCUR):

For a criticality to occur, the mass in the compressor would have to increase to greater than 10.35 kg. The material then would have to be moderated and the deposit would have to reflected

CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY. CONCENTRATION, ETC.):

Enrichment and Mass

ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE OF CRITICAL MASS):

Estimated enrichment is 1.5 weight percent U-235, the mass is estimated at 41 grams. The form of the material would be UF6. The optimum safe mass and critical mass at an enrichment of 1.5 % U-235 is 4.5 Kg and 16.502 Kg respectively.

NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES

There were no NCSA controls on the identified equipment because the enrichment in the equipment was to be less than 1 weight percent U-235 in an operating cascade. In the current configuration it is not credible that enrichment would be exceeded. The deficiency was the equipment was not isolated from equipment that is allowed to see enrichment greater than 1 weight percent U-235.

CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEM AND WHEN EACH WAS IMPLEMENTED:

The Plant Shift Superintendent directed the "A" booster isolated. The equipment was sampled and found below 1% U-235. Engineering continues to investigate the issue.

The NRC Resident Inspector was notified and the DOE Representative will be informed.


* * * UPDATE ON 06/07/01 AT 1313 ET BY RICHIE TAKEN BY MACKINNON * * *

After further review this is not reportable because an additional evaluation determined the enrichment in the affected equipment did not exceed 1 weight percent U235, and the plant condition remained within that assumed by the NCSA and SAR. Therefore no violation occurred. R3DO (B. Clayton) & NMSS EO (John Hickey) notified.

The NRC Resident Inspector was notified of this update by the Certificate Holder.

AN UNANALYZED CONDITION WAS FOUND WHEN AN EXISTING PIPE TRENCH BLOCKOUT PATHWAY SEPARATING TWO ROOMS WAS FOUND TO BE BLOCKED.

After reviewing the Unit 2 flooding calculation (environmental calculations for Auxiliary Feedwater and performing a walkdown of the area, it was determined that the calculation model which assumed an existing pipe trench blockout pathway separating the 2 rooms to be an open pathway. This pathway was found to be blocked leading to an unanalyzed condition.

A PRA evaluation was performed for this condition. The result of this evaluation shows that the potential degraded condition due to the sealed pathway and missing backwater check valves in the drain lines does not pose a significant increase in the core damage risk. However, an additional review on May 15, 2001, it was deemed that the cumulative risk increase is potentially significant assuming the condition existed since initial evaluation. Therefore, this issue is being conservatively reported pursuant to 10 CFR 50.72 (ii)(B).

No Technical Specification OPERABILITY issues are identified as a result of this event. Additionally this event has been evaluated per GL 91-18 and actions are being taken to be in compliance with the flooding calculations.

The NRC Resident Inspector will be notified.

* * * RETRACTED AT 1657 EDT ON 6/14/01 BY STEVEN SEWELL TO FANGIE JONES * * *

"On 5/18/01 at 1508 hours, Comanche Peak Unit 2 reported an unanalyzed condition per 10CFR50.72(b)(3)(ii)(B) [EN# 38009). Specifically, the reported condition involved Unit 2 flooding/environmental calculations for the Auxiliary Feedwater (AFW) system that assumed an existing pipe trench blockout pathway separating 2 rooms to be an open pathway. During a walkdown of the area, it was determined that the pathway was sealed and backwater check valves did not exist in all floor drain lines from the three AFW pump rooms. This as-found configuration led to an unanalyzed condition where all three AFW pumps could be potentially incapacitated by a piping break in any one of the AFW pump rooms. This condition was determined to have existed since initial licensing and an initial, conservative, PRA evaluation of this condition determined that the cumulative risk increase was potentially significant.

"Subsequently, a detailed deterministic analysis was performed to determine the consequence of flooding given the as found conditions. That evaluation shows that in no case is there a flooding scenario that results in the loss of all three AFW pumps. Comanche Peak Unit 2 has three pump trains (two 50% capacity motor driven pumps and one 100% capacity steam turbine driven pump). The worst case scenario is flooding in one of the motor driven AFW pump rooms which results in the loss of both motor driven pumps. In this case, the evaluation shows that the turbine driven pump is not disabled. Further, the flood waters do not adversely impact any other safety related equipment modeled in the PRA. The deterministic evaluation further concluded that a break occurring in the turbine driven pump room does not adversely impact either of the motor driven pump rooms.

"The results of this evaluation show that the potentially degraded condition due to the sealed pathway and missing backwater check valves does not pose a significant core damage risk increase as a result of potential consequential equipment failures. Therefore. Comanche Peak requests that the 5/18/01 10CFR50.72(b)(3)(ii)(B) reportable event for Unit 2 be retracted."

The licensee notified the NRC Resident Inspector. The R4DO (John Pellet) has been notified.