Techniques employed for detection of hot particles in the marine environment.
During the decommissioning of the Maine Yankee nuclear plant, several methods were developed and employed to survey for hot particles in the marine environment surrounding the site. The methods used and the sensitivities achieved in the search for environmentally dispersed particles during the various decommissioning activities performed are described in detail. Surveys were performed on dry soil, exposed marine sediment and submerged marine sediment. Survey techniques ranged from the use of the basic NaI detector coupled to a count rate meter to an intrinsic germanium detector deployed in a submarine housing coupled to a multi-channel analyser. The initial surveys consisted of collecting samples of marine sediment, spreading them out over a 1 m2 surface in a thin layer, and scanning the deposited sediment by hand using a 5 cm by 5 cm NaI detector coupled to a standard count rate meter. This technique was later replaced by walkover scans with the 5 cm by 5 cm NaI detector moved in a serpentine pattern over the sediment surface. By coupling the detector to a 'smart meter', an alarm set point could be used to alert the surveyor to the presence of a particle within the instrument's field of view. A similar technique, with the detector mounted in a watertight housing secured to the end of a pole, was also employed to scan underwater locations. The most sensitive method developed for performing underwater surveys was the use of the intrinsic germanium detector placed in a submarine housing. Detailed descriptions of the methods employed and the results obtained are presented. This work demonstrates that there are several approaches to surveying for discrete particles in the marine environment and the relative merits of each are considered.
Pillsbury
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Final Status Survey, Maine Yankee, 321 Old Ferry Road, ME 04578, USA.
D004781:Environmental Exposure; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D005857:Germanium / Q000737:chemistry; D006801:Humans; D008281:Maine; D011210:Power Plants; D011832:Radiation Injuries / Q000517:prevention & control; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods*; D011850:Radioactive Waste / Q000032:analysis*; D012306:Risk; D018570:Risk Assessment / Q000379:methods*; D012680:Sensitivity and Specificity; D012974:Sodium Iodide / Q000737:chemistry; D018505:Waste Management / Q000379:methods*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D011850:Radioactive Waste; D014875:Water Pollutants, Radioactive; D005857:Germanium; D012974:Sodium Iodide