Field tests of passive alpha detectors at the Nevada Test Site for screening of radiologically contaminated soils
- Oak Ridge National Lab., TN (United States). Health Sciences Research Div.
Two types of passive alpha detectors, developed for indoor radon measurements, have been field tested for applications to screening of alpha-emitting contaminants (e.g. Pu, Am, U, Th) in soils. Electret Ionization Chambers (EICs) measure air ionization due to alpha emission from the soil surface, while Alpha Track Detectors (ATDs) register alpha particles as microscopic damage pits. The detectors are inexpensive, rugged, simple to use, and respond reproducibly and linearly over three orders of magnitude of contamination levels. It was found that alpha emission rates per unit of soil activity varied widely with soil composition. Procedures were developed for establishing site-specific calibrations for each type of detector. Both types of detectors were deployed directly on the surface of soils contaminated with {sup 239}Pu and {sup 241}Am at the Nevada Test Site. Deployment times of 5 minutes to 5 days were necessary in order to reliably detect contamination levels of 100nCi/g (Pu + Am) down to background ({approximately}22pCi/g total alpha). The advantages of the EIC detectors were found to be their immediate on-site readout capability, while the primary advantages of the ATD detectors were their insensitivity to beta/gamma radiations and radon and their ability to identify hot particles. Techniques were developed to discriminate against environmental radon and background {alpha}/{beta}/{gamma} radiations. ATDs in the form of long narrow strips, deployed in stake-driven holes, were used to obtain contamination depth profiles quickly and reproducibly.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 276417
- Report Number(s):
- CONF-950209--
- Country of Publication:
- United States
- Language:
- English
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