05000416/LER-2012-006
| Sequential Revmonth Day Year Year Month Day Year N/Anumber No. N/A | |
| Event date: | 07-25-2012 |
|---|---|
| Report date: | 08-23-2012 |
| 4162012006R00 - NRC Website | |
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A. REPORTED CONDITION
On July 25, 2012, at 1534 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.83687e-4 months <br /> Central Daylight Time (CDT), Grand Gulf Nuclear Station (GGNS) was in Mode 1 operating at approximately 100 percent power. During performance of the annual physical inventory of special nuclear material (SNM), the determination was made that a source range monitor (SRM) detector, serial number 10F007J5, was not in its expected storage location. While the investigation concluded that the SRM was likely removed from the 208 foot elevation Auxiliary building temporary Item Control Area (ICA) location during cleanup at the end of Refueling Outage 18 (RF18), along with other material that was stored in the area, and discarded as radioactive waste, this condition is being reported in accordance with 10 CFR 20.2201 (a) (1) (ii) as a loss of licensed material of a quantity greater than ten times the quantity specified in Appendix C to 10 CFR Part 20. Telephone notification was made on July 25, 2012, to the Nuclear Regulatory Commission (NRC) Emergency Notification System (ENS) pursuant to 10 CFR 72.74, 10 CFR 74.11, and 10 CFR 20.2201 (a) (1) (ii). This written report is being submitted within 30 days of the telephone notification in accordance with 10 CFR 20.2201(b).
B. DESCRIPTION OF LICENSED MATERIAL INVOLVED
SRM detector 10F007J5 was originally received on site November 2011. The SRM was installed during RF18 in the Spring of 2012 and subsequently failed testing. Therefore, the SRM detector was removed April 2012 and was not in the reactor core during startup. It was determined that the detector was placed into storage until it was identified missing July 25, 2012. The SRM detector is a sealed fission chamber containing uranium oxide (solid UO2) material. Based on the original Shipper's Certification for Radioactive Material, the SRM detector contained an estimated maximum total activity of 0.187 microcuries (all isotopes, including U-235) and 0.00292 grams total Uranium.
C. CIRCUMSTANCES UNDER WHICH THE LOSS OCCURRED
In April 2012, SRM detector 10F007J5 was moved to core location 50-31 (Source Range Monitor 'C' location) per SNM Tracking Sheet (STS) STS-1-19-10, step 41, during RF18. Subsequently, it was discovered that the SRM had failed testing. Prior to drywell closeout, during RF18, the defective detector was moved from the core to a temporary SNM ICA storage area on 208 foot elevation of the Auxiliary building, per SNM Tracking Sheet STS-1-19-10, step 47 and placed into a radioactive material bag in a normally locked storage cage.
During performance of the 2012 annual SNM physical inventory, a discrepancy between the SNM database and physical inventory was discovered regarding the location of SRM detector 10F007J5 (reference CR-GGN-2012-09405).
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D. DISPOSITION OF LICENSED MATERIAL INVOLVED
Based on the investigation, review of inventory results, and interviews with responsible personnel, it was concluded that SRM detector 10F00735 was removed from the 208 foot elevation Auxiliary Building SNM ICA during cleanup at the end of RF18, along with other material that was stored in the area, and discarded as radioactive waste.
The 2012 SNM inventory sheets have been reconciled with the physical SNM inventory, and appropriate notifications and reports have been made.
E. EXPOSURES
SRM detector 10F00735 contained a maximum total activity of approximately 0.187 microcuries (all isotopes) and 0.00292 grams total Uranium. The licensed material in the detector that could not be accounted for, was inside the detector that was properly handled as a device containing radioactive material. Since the detector containing the licensed material was maintained in the controlled waste process stream (i.e., packaging, transportation, and disposal of radioactive materials), no unregulated exposures occurred to persons in unrestricted areas. In addition, given that the detector was not highly irradiated (not in the reactor core during reactor startup), its contribution to the dose received by any radiation workers involved in the waste handling process was negligible.
F. ACTIONS TAKEN TO RECOVER THE MATERIAL
A thorough inspection of potential detector storage locations was conducted, and historical SNM related documentation was reviewed. A detailed search plan was developed and areas to be searched prioritized based on likelihood of locating the missing SNM. The 208 foot elevation Auxiliary building radioactive material storage area search included removal of all RF18 material and performance of detailed housekeeping within the caged storage area. The trash located in the Energy Solutions sea-land located behind the Radwaste building was removed, sorted and searched. A search of the radioactive material (RAM) tool storage and control rod drive (CRD) rebuild room on 166 foot elevation Auxiliary building was performed. The RAM storage area on 185 foot elevation Auxiliary building, hot machine shop on 93 foot elevation Turbine Building, and the 93 foot elevation Radiation Protection equipment storage area were also searched. The trash in Energy Solutions sea-land ESUU 200787 located near the mausoleum was searched and no bagged trash was found. Finally, an Entergy Radiation Protection Specialist performed a search for the SRM at the Disposal Facility. The missing SRM was not located.
Based on the investigation, it was concluded that SRM detector 10F00735 was removed from the 208 foot elevation Auxiliary Building SNM ICA during clean up at the end of RF18, along with other material that was stored in the area, and discarded as radioactive waste.
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G. PROCEDURES OR MEASURES TO ENSURE AGAINST RECURRENCE
The ICA storage location was locked and additional signage installed. Corrective action to preclude recurrence is to revise procedure 17-S-02-300 to include Reactor Engineering STS sign-off steps for briefing the requirements for posting, segregation, and identification of SNM and ICAs, and for completion of the SNM transfer, verifying proper SNM and ICA identification, posting, and segregation.
Condition Report CR-GGN-2012-09405, initiated July 25, 2012, requires a Root Cause Evaluation which will address any additional actions to preclude recurrence of similar events.
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