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Use of passive alpha detectors to screen for uranium contamination in a field at Fernald, Ohio

Description: This paper reports the results from a field test of newly developed techniques for inexpensive, in situ screening of soil for alpha contamination. Passive alpha detectors that are commercially available for the detection indoor airborne alpha activity (i.e., {sup 222}Rn) have been modified so they can be applied to the detection of alpha contamination on surfaces or in soils. Results reported here are from an intercomparison involving several different techniques with all measurements being made at the same sites in a field near the formerly used uranium processing facility at Fernald, Ohio, during the summer of 1994. The results for two types of passive alpha detector show that the quality of calibration is improved if soils samples are milled to increase homogeneity within the soil matrices. The correlation between laboratory based radiochemical analyses and quick, field-based screening measurements is acceptable and can be improved if the passive devices are left for longer exposure times in the field. The total cost per measurement for either type of passive alpha detector is probably less than $25 and should provide a cost-effective means for site managers to develop the information needed to find areas with remaining alpha contamination so resources can be allocated efficiently.
Date: June 1995
Creator: Dudney, C. S.; Meyer, K. E.; Gammage, R. B.; Wheeler, R. V.; Salasky, M. & Kotrappa, P.
Partner: UNT Libraries Government Documents Department

Evaluation of passive alpha detectors for sensitive/inexpensive/fast characterization of radiological contamination on surfaces and in soils

Description: Passive alpha-particle detectors, originally developed for indoor radon measurements, offer the potential for cost-effective and sensitive measurements of radiological contamination in soils and on surfaces for field screening and radiological survey applications. We have carried out field demonstrations of electret ionization chambers (EIC`s) and alpha track detectors (ATD`s). The EIC`s offer the advantages of immediate on-site readout, good sensitivity, ruggedness, and simplicity of operation. The use of parallel screened and unscreened EIC measurement allows the separation of alpha-particle response from radon/gamma/beta response. The advantages of the ATD`s include the potential for hot-particle counting, permanent records of contaminated and post-remediation activity levels, and inexpensive depth profiling of contamination in soil. At this time, the ATD`s are routinely shipped to the vendor after exposure in the field for processing and readout. It is feasible that the necessary processing and readout equipment could be deployed in a mobile laboratory for fast on-site analysis. We will present results from environmental measurements at the Nevada Test Site and indoor surface contamination measurements carried out at ORNL.
Date: April 1, 1994
Creator: Meyer, K. E.; Gammage, R. B.; Dudney, C. S.; Kotrappa, P.; Wheeler, R. & Salasky, M.
Partner: UNT Libraries Government Documents Department

In-situ passive monitoring of alpha-emitting radionuclides

Description: Electrets and alpha-track detectors (ATDs) show considerable promise for inexpensive passive monitoring of alpha contamination on man-made surfaces or in soil. At the stringent Department of Energy (DOE) limit of 100 dpm/100 cm{sup 2}, the electret voltage drops 10 V in about 4 hours; 10 V is readily quantifiable since any reading of electret voltage is accurate to {plus_minus}l V. An analogous signal-to-noise ratio for the ATDs is obtained after an exposure time of about 3 hours. The alpha-track registration efficiency for CR-39 type plastic is about 70% with the background track density averaging 13 tracks/cm{sup 2}. Measurements for intercomparison were performed with electrets, ATDS, and conventional survey meters on a contaminated vinyl floor and a concrete loading dock. Agreement between different types of detector readings was satisfactory. Surface soil measurements, using an exposure time of 1 day, can detect contamination of just a few pCi/g. Preliminary horizontal mapping was conducted within and at the boundary of a plutonium contaminated area at the DOE Nevada Test Site (NTS). The means of making vertical profiles of subsurface contamination are being explored. Some problems that have to be overcome involve interference from natural radon, variable soil moisture, preventing moisture condensation, wide extremes of ambient temperature and wind-driven shifting of soil.
Date: June 1, 1993
Creator: Gammage, R. B.; DePriest, J. C.; Murray, M. E.; Wheeler, R. V.; Salasky, M. R.; Dempsey, J. C. et al.
Partner: UNT Libraries Government Documents Department