ENS 40750
ENS Event | |
|---|---|
13:00 May 14, 2004 | |
| Title |
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| Event Description | THIS IS NOT A NEW REPORT.
This event report was originally withheld from public release under the NRC's policy for protecting sensitive unclassified information. The NRC has reevaluated this policy and is now making this event report available to the public with suitable redactions.
91-01 BULLETIN - LOSS OF CRITICALITY SAFETY CONTROLS An Integrated Safety Analysis (ISA) review being performed for a system modification identified a previously unidentified failure mode for a piece of Safety Related Equipment (SRE). The SRE item (conductivity probe) is in place to detect and prevent the transfer of moderating materials to a fissile material storage column. The conductivity probe was subsequently tested and found to not meet the currently required performance criteria (i.e. the conductivity probe was not capable of detecting certain moderating materials that could be present in the fissile material). The operation was already in a shutdown state and all fissile material had been removed from the system when the test was performed on the probe. Safety significance of the event: The safety significance is very low since the system was currently shutdown and the identified failure mode has not occurred since startup of the operation in 1999. Brief scenario(s) of how criticality could occur: Failure of the piece of SRE could only result in a criticality if a subsequent unlikely event were to also occur resulting in a large spill of fissile material. Controlled parameters: Moderation and Geometry Estimated amount, enrichment, form of licensed material (include process limit and % worst case critical mass): Uranium compounds in the column would be 43 times minimum critical mass if spill of materials in full column occurred. Process limit is limited by geometry of equipment Control(s) or control system(s) and the failure(s) or deficiencies: A fissile material transfer line is monitored (for moderation) such that the transfer of moderating materials into a column is prevented. The monitoring equipment was found to not be compatible for all moderating materials in the system preventing it from halting the transfer of moderating materials into the equipment under certain postulated upset conditions. Corrective actions taken and when was each was implemented: The conductivity probe was tested in the newly identified failure mode and was found to not respond adequately. The system was already in a shutdown state and all fissile material had been removed from the system when the test was performed on the probe. Compensatory measures (both administrative and engineered) were drafted and reviewed by the plant safety review committee. The system remains shutdown until all compensatory measures are approved and in place. Licensee notified the NRC Resident Inspector.
THIS IS NOT A NEW REPORT. This event report was originally withheld from public release under the NRC's policy for protecting sensitive unclassified information. The NRC has reevaluated this policy and is now making this event report available to the public with suitable redactions. |
| Where | |
|---|---|
| Nuclear Fuel Services Inc. Erwin, Tennessee (NRC Region 2) | |
| License number: | SNM-124 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+4.12 h0.172 days <br />0.0245 weeks <br />0.00564 months <br />) | |
| Opened: | Randy Shackelford 17:07 May 14, 2004 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | May 11, 2008 |
| 40750 - NRC Website | |
Nuclear Fuel Services Inc. with Response | |
WEEKMONTHYEARENS 407502004-05-14T13:00:00014 May 2004 13:00:00
[Table view]Response
2004-05-14T13:00:00 | |