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A method for determining soil gas {sup 220}Rn (THORON) concentrations

Journal Article · · Health Physics
 [1]
  1. Dept. of Energy, New York (United States)
A technique has been developed to accurately, precisely, and quickly measure soil gas {sup 220}Rn using commercially available grab-sample scintillation detectors. The method requires two counting periods for each sample: a 1-min count as soon as the sample has been drawn into a scintillation cell, followed by a 5- or 10-min count at least 5 min after the soil gas sample has been obtained. The {sup 222}Rn concentration is determined from the second count. The counts in the first counting period (1-min) due to {sup 222}Rn and its progeny are calculated from the known {sup 222}Rn concentration and then subtracted from the total counts obtained in the first counting period. The remaining counts are due to {sup 220}Rn and its progeny and are used to calculate the {sup 220}Rn concentration. The overall uncertainty when using this method to measure typical soil gas {sup 220}Rn and {sup 222}Rn concentrations [> {approximately}5 kBq m{sup -3} (130 pCi L{sup -1})] was determined to be 19.8% and 10.8% (90% confidence levels), respectively, from analyses of duplicate field measurements. The lowest {sup 220}Rn concentrations that can be measured using this technique while maintaining an overall error no greater than about 30% is {approximately}500 Bq m{sup -3} (13 pCi L{sup -1}), assuming an approximately equal {sup 222}Rn concentration. The {sup 220}Rn measurement uncertainty at this concentration level decreases to {approximately} {+-} 20% if at least three measurements sampled in series are arithmetically averaged. The uncertainty in the {sup 220}Rn measurement at low levels is proportionately affected by the relative concentration of {sup 222}Rn present. 11 refs., 2 figs., 1 tab.
OSTI ID:
369950
Journal Information:
Health Physics, Journal Name: Health Physics Journal Issue: 6 Vol. 68; ISSN HLTPAO; ISSN 0017-9078
Country of Publication:
United States
Language:
English