Validation of Non-Invasive Waste Assay System (Gamma Box Counter) Performance at AECL Whiteshell Laboratories - 13136
- Atomic Energy of Canada Limited, Pinawa, Manitoba, R0E 1L0 (Canada)
Low-level radioactive waste (LLW) in solid form, resulting from decommissioning and operations activities at AECL's Whiteshell Laboratories (WL), is packaged in B-25 and B-1000 standard waste containers and characterized before it is shipped to an on-site interim storage facility, pending AECL decisions on long term management of its LLW. Assay of the waste packages before shipment contributes to an inventory of the interim storage facility and provides data to support acceptance at a future repository. A key characterization step is a gamma spectrometric measurement carried out under standard conditions using an automated, multi-detector Waste Assay System (WAS), purchased from Antech Corporation. A combination of ORTEC gamma acquisition software and custom software is used in this system to incorporate multiple measurements from two collimated high-resolution detectors. The software corrects the intensities of the gamma spectral lines for geometry and attenuation, and generates a table of calculated activities or limits of detection for a user-defined list of radioisotopes that may potentially be present. Validation of WAS performance was a prerequisite to routine operation. Documentation of the validation process provides assurance of the quality of the results produced, which may be needed one or two decades after they were generated. Aspects of the validation included setting up a quality control routine, measurements of standard point sources in reproducible positions, study of the gamma background, optimization of user-selectable software parameters, investigation of the effect of non-uniform distribution of materials and radionuclides, and comparison of results with measurements made using other gamma detector systems designed to assay bulk materials. The following key components of the validation process have been established. A daily quality control routine has been instituted, to verify stability of the gamma detector operation and the background levels. A test box containing plywood (specific gravity 0.5) with holes for reproducible positioning of known point sources has been constructed and used in several configurations. Gamma spectra have been processed multiple times with user-adjustable parameters set to a variety of values to gain agreement on the most appropriate settings. A similar optimization process was followed with the custom software provided by the instrument manufacturer to reach agreement on the most stable settings for reliable results. Measurements made with the Canberra In-Situ Object Counting System (ISOCS) instrument were compared with the WAS results as part of an estimate of instrument precision and accuracy. The validation report will conclude with recommendations for the configuration, appropriate use and limitations of the Waste Assay System. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22224914
- Report Number(s):
- INIS-US-13-WM-13136; TRN: US14V0355045869
- Resource Relation:
- Conference: WM2013: Waste Management Conference: International collaboration and continuous improvement, Phoenix, AZ (United States), 24-28 Feb 2013; Other Information: Country of input: France; 7 refs.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ACCURACY
ATOMIC ENERGY OF CANADA LTD
COMPARATIVE EVALUATIONS
COMPUTER CODES
GAMMA SPECTRA
LOW-LEVEL RADIOACTIVE WASTES
OPTIMIZATION
POINT SOURCES
QUALITY CONTROL
RADIOISOTOPES
SOLID WASTES
VALIDATION
WASTE STORAGE