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Title: Calibration and operation of the PNL Barrel Assayer

Technical Report ·
DOI:https://doi.org/10.2172/5514575· OSTI ID:5514575

Pacific Northwest Laboratory operates a Barrel Assayer to measure the radionuclide content of 208-liter waste drums. This mobile apparatus is designed to provide quantitative information on each radioisotope in a drum and to recognize and locate hot spots within the drum. A lead-collimated intrinsic-germanium detector mounted on a moveable platform vertically scans a rotating drum for gamma-ray activity while 62 stationary {sup 10}BF{sub 3} tubes measure neutrons emitted by transuranic isotopes within the waste. Several approaches have been used to document the controls under which the Barrel Assayer has been operated from February 1989 through December 1990. Resin-filled 208-1 calibration barrels containing known quantities of {sup 60}Co, {sup 137}Cs, and {sup 134}Cs were measured by the Barrel Assayer and found to be well within 25% of the known values. A thorium nitrate standard that served as the secondary, or field, standard verified that the detector has been within calibration during the period from February 1989 through December 1990. In previous testing, 23 waste drums were assayed at several commercial nuclear power plants. Subsequently, aliquots from the top, middle, and bottom of the barrels were analyzed. The ratio of grab-sample concentration to direct-assay concentration averaged {minus}1.6 for one plant and +1.3 for another. Results using the Barrel Assayer were also comparable to those obtained using Safeguards Security's Segmented Gamma-ray Scanner (SGS) system in a cross-calibration experiment performed by a third party on several drums containing TRU wastes. 6 refs., 6 figs., 9 tabs.

Research Organization:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE; USDOE, Washington, DC (United States)
DOE Contract Number:
AC06-76RL01830
OSTI ID:
5514575
Report Number(s):
PNL-7739; ON: DE91016053
Country of Publication:
United States
Language:
English