05000282/LER-2009-009
| Prairie Island Nuclear Generating Plant Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Initial Reporting | |
| ENS 45633 | 10 CFR 20.2201(a)(1)(ii) |
| 2822009009R00 - NRC Website | |
DOCKET NUMBER (2) 05000 282 YEAR 09 -- 009 -- 0 LER NUMBER (6)
EVENT DESCRIPTION
During the 2009 radioactive source inventory at Prairie Island Nuclear Generating Plant (PINGP), radiation protection (RP) personnel determined that two sources were missing that are greater than 10 times the quantity specified in 10 CFR 20 Appendix C. These two sources included a 0.07 microcurie (uCi) U-234 source installed in a radiation monitor detector and a 2 uCi mixed gamma standard that contains 0.09 uCi of Am-241. Four additional sources that do not exceed ten times any quantity specified in 10 CFR 20 Appendix C were also determined to be missing. The NRC was notified of this inventory discrepancy via the event notification system (event number 45633) on January 18, 2010 with updates provided January 19 and 20, 2010.
The 2 uCi mixed gamma standard contains 0.09 uCi of Am-241. This source is held in a 60 milliliter (ml) vial and is normally stored in the Hot Chemistry Lab. After searching for the gamma standard, it was located in the Hot Chemistry Lab on January 19, 2010.
The 0.07 uCi U-234 source is a self checking source imbedded in a high range ion chamber detector.
This detector is normally stored in the Hot Instrumentation and Control Shop. Prior to December 12, 2006, this detector was installed as an area radiation monitor. A thorough search of potential detector storage and disposal locations was conducted, RP personnel were interviewed, and related documentation was reviewed. This investigation concluded that the detector containing the missing U-234 source was most probably shipped offsite as low level radioactive waste in the period between September 2008 and September 2009.
EVENT ANALYSIS
Extensive effort to locate the missing sources resulted in the mixed gamma standard being accounted for and the determination that the U-234 source was lost. It is highly probable that the U-234 source was shipped offsite as low level radioactive waste.
This event did not affect the ability of plant equipment to perform its required safety functions. Thus, this event is not a Safety System Functional Failure.
SAFETY SIGNIFICANCE
The mixed gamma standard was accounted for in the lab where it is normally stored. No unregulated exposures occurred to persons in unrestricted areas due to this source.
The U-234 source is contained internal to the radiation detector. The probability for unregulated exposures to persons in unrestricted areas due to this source is considered low based on the high DOCKET NUMBER (2) 05000282 YEAR 09 -- 009 -- 0 LER NUMBER (6) probability that the source was disposed of via normal radwaste processes and preliminary dose reconstruction analysis.
CAUSE
The significance that PINGP had assigned to the source control program did not align with the potential impact associated with the loss of control of radioactive sources. Examples included weaknesses in process controls, lack of adequate communication between RP personnel and management, inconsistency between site and fleet procedures, and lack of supervisory oversight.
CORRECTIVE ACTION
Immediate corrective action was an extensive search for the missing sources which included further inventory review, personnel interviews and offsite searches. This search accounted for the 2 uCi mixed gamma standard.
Administration of the radioactive source control program will be improved by eliminating the site procedure and upgrading the fleet procedure. Procedure additions will include a source checkout log, a disposal form, and additional guidelines for completing the source inventory. Source inventories will be administered and reviewed by RP supervision. Additionally, source inventories will be conducted per plant work control processes.
PREVIOUS SIMILAR EVENTS
In 2003, a high range detector containing an internal U-234 source could not be located. The source met the threshold of being greater than ten times the quantity specified in 10 CFR 20 Appendix C.
However, the source was located prior to making the thirty-day telephone report.