05000413/LER-2002-005
| Catawba Nuclear Station, Unit 1 | |
| Event date: | 06-25-2002 |
|---|---|
| Report date: | 07-25-2002 |
| Initial Reporting | |
| 4132002005R00 - NRC Website | |
Background:
Catawba Nuclear Station Units 1 and 2 are four loop Westinghouse Pressurized Water Reactors [EIIS:RCT]. This report is being submitted pursuant to 10CFR20.2201(b) which addresses loss of licensed material. This regulation states that a telephone report is required:
(i) Immediately after the occurrence becomes known to the licensee, any lost, stolen, or missing material in an aggregate quantity equal to or greater than 1000 times the quantity specified in Appendix C of 10CFR Part 20 under such circumstances that it appears to the licensee that an exposure could result to persons in unrestricted areas; or (ii) Within thirty days after the occurrence of any lost, stolen, or missing licensed material becomes known to the licensee, all licensed material in a quantity greater than 10 times the quantity specified in Appendix C to Part 20 that is still missing at this time.
A written report is required within 30 days after the telephone report.
The 10CFR20 Appendix C quantity for Americium-241 (Am-241) is 0.001 microCurie. The quantity involved in this incident is 0.0244 microCurie (24.4 times the Appendix C quantity).
This event does not meet the telephone report criteria of (i) above since the quantity involved is not greater than 1000 times the 10CFR20 Appendix C quantity. It does meet the criteria of (ii) above since the quantity is more than 10 times the 10CFR20 Appendix C quantity.
Since recovery of the material was not expected, the thirty day telephone report was made immediately. This report was made on June 25, 2002 (Event Number 39018).
Prior to this event Catawba Units 1 and 2 were operating in Mode 1 at a nominal power level of 100%. There was no equipment out of service on either unit that had any effect on this event. This event had no effect on the safe operation of the plant.
The following numbered paragraphs address the information required by 10CFR20.2201(b).
7 (b)(i) A description of the licensed material involved, including kind, quantity, and chemical and physical form.
The licensed material involved was a solid Am-241 (serial number 63281B-85) calibration source containing 0.0244 microCuries of activity. The source configuration was a 10 centimeter (cm) by 10 cm active area on a 6 millimeter (mm) thick plate, a 1 cm wide by 3 mm thick frame and a 3 mm thick backing plate. The source was covered by a 0.5 milligram (mg) per square centimeter mylar film. The mylar source covering which contained approximately 85 percent of the source activity is missing.
(b)(ii) A description of the circumstances under which the loss or theft occurred. (Event Description) April 18, 2002 � Two Radiation Protection (RP) technicians were performing a usability review of a draft procedure for set-up, calibration and response check of PCM- 2 whole body monitors. One of the calibration sources used was a 0.0244 microCurie Am-241 alpha source (as described above). The technicians performed enough of the procedure to determine that the procedure was adequate (they were not expected to perform the entire procedure). Data recorded on April 18, 2002 and subsequently reviewed (on June 25, 2002) indicated that the Am- 241 alpha source had the expected amount of activity when it was initially used during the procedure usability review. Later in the procedure usability review, the data indicated the alpha source activity significantly decreased but this was not recognized at the time. After the procedure review was completed, the source was placed in a source box and stored in a designated storage location. No further work was done to the PCM-2 until late June 2002.
June 24, 2002 Two RP technicians and a staff RP person obtained the Am-241 source and started preparations for final PCM-2 calibration and technician qualification which were scheduled for the next day. The source was placed on one of the PCM-2 7 June 25, 2002 detectors. The technician removed the source at the completion of the count and noticed the source frame had separated from the source plate. He went to his shop area and repaired the source by removing several small pieces of crimpled mylar underneath the source frame and a small piece of mylar on one corner. He returned with the repaired source and the group (two RP technicians and one RP staff person) discussed what he had done. It was decided that alpha surveys of the work area and the personnel who handled the source would be performed. Results indicated no alpha contamination in the work area or on any of the individuals who had handled the source. The source edges and back were also smeared and no significant activity was noted. After technicians completed preparations for the next day's calibration of the PCM-2, the source was placed in a source box and stored in a designated storage location.
An RP technician, RP supervisor (acting as task evaluator) and a RP staff person started a full calibration of a PCM-2. About half way into the procedure the technician placed the Am-241 source on one of the PCM-2 detectors. The technician noticed the alpha curve was not as expected. He continued to the next steps in the procedure where the detector efficiencies are calculated and displayed on a data table. The alpha efficiency was 0.23% for PCM-2 detector 8 and 0.31% for PCM-2 detector 11. Previous calibrations had shown efficiencies from 9 to 11%. Work was stopped, RP management was notified, and an investigation was initiated.
(b)(iii) A statement of disposition, or probable disposition, of the licensed material involved.
The licensee believes the loss of licensed material occurred on April 18, 2002 while two RP instrument technicians were using the Am-241 source to walk through a newly developed procedure for calibrating a PCM-2 whole body monitor.
The procedure directs the user to place the Am-241 calibration source (no holder) in contact with the center of a PCM-2 detector. No source holder is used for the alpha source due to the short range of alpha particles in air. It is believed that double sided foam tape was used on each side of the source frame to secure it to the detector screen. The tape was probably too wide for the frame and stuck to the mylar face. When the source was removed from the detector screen, it is likely that some of the tape stuck to the screen and tore off the mylar on the source face. The tape and mylar were probably placed in a trash receptacle.
Two trash streams are possible. Contaminated trash (items that were used in a contaminated area or items that have any potential of being contaminated) is collected and shipped offsite for processing and disposal as radioactive waste. Clean trash (items that have not been in a contaminated area) is collected and monitored in a gamma sensitive bag monitor. Items not passing the bag monitor are temporarily stored and eventually sent off site for processing and disposal. Items passing the bag monitor are free released, collected by a local disposal company and sent to the county landfill. The licensee does not know which waste stream the source may have gone to if placed in a trash receptacle.
(b)(iv) Exposures of individuals to radiation, circumstances under which the exposures occurred, and the possible total effective dose equivalent to persons in unrestricted areas.
No individuals are believed to have been exposed to this material.
A dose assessment was conducted assuming a hypothetical maximally exposed individual.
The dose assessment concluded that external exposure would be negligible because the primary radiation is alpha which cannot penetrate 7 mg/square centimeter shallow dose equivalent (SDE).
Am-241 has secondary low energy photons that produce low dose rates for the source strength. The dose from an external pathway is considered negligible.
Internal exposure varies according to the intake path. The dose assessment calculated the internal dose would be 74 mrem committed effective dose equivalent (CEDE) if ingested or 9 rem CEDE if inhaled.
7 The total effective dose equivalent (TEDE) is equal to the sum of the CEDE and the deep dose equivalent (DDE) (external exposure). Because the DDE is negligible, the TEDE is equal to the CEDE. Given the probable disposition and physical characteristics of this source, it is unlikely that this source was ingested or inhaled. Therefore, it is not considered credible that any individual could receive the maximum calculable dose from this source.
(b)(v) Actions that have been taken or will be taken to recover the material.
Five boxes containing clean trash that alarmed the bag monitor have been surveyed for the missing source, but the source was not located.
Future recovery of the source is considered unlikely.
(b)(vi) Procedures or measures that have been, or will be, adopted to ensure against a recurrence of the loss or theft of licensed material. (Corrective Actions) Training will be given to Radiation Protection Technicians on precautions required for handling sealed sources. An alpha source holder will be fabricated and used for PCM-2 calibration.
Causal Factors An investigation determined that this event was caused by an inadequate program for handling, storage, and inventory of this alpha source.
Corrective Actions
Immediate 1. Sources of similar design were verified to be present and intact.
Planned 1. Training will be given to Radiation Protection Technicians on precautions required for handling sealed sources.
7 2. An alpha source holder will be fabricated and used for PCM-2 calibration.
Safety Analysis
This event had no effect on the safe operation of the plant. There is no Core Damage Frequency (CDF) aspect to this event. There was no Safety System Functional Failure associated with this event.
This source would present no danger to the health and safety of the public unless it were inhaled or ingested. Inhalation or ingestion of the source is considered unlikely due to the probable disposition and physical characteristics of the source. The source was probably discarded into the solid waste stream of the plant which would not contact members of the public. The physical size, shape, and configuration of the source would make ingestion or inhalation unlikely.
Additional Information
There have been no similar events at Catawba Nuclear Station in the past 24 months, therefore, this event is considered tc be non- recurring.
There are no EPIX reportable equipment failures associated with this event. Energy Industry Identification System (EIIS) codes are identified in the text within brackets [ I. This event is documented in Catawba Corrective Action Program (PIP) Serial Number C-02-03620.
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