Measurement of Radon Concentration in the near-surface Soil Gas by CR-39 Detectors
Kang, D.W.;Kim, H.G.;
ABSTRACT
A series of experiments is performed to measure radon concentration in the near-surface soil gas at the four locations (Cheju-Si, Seoguipo-Si, Taejeong-eup, Seongsan-eup) in Cheju Island, using CR-39 detectors placed inside radon cups. Two types of radon cups are installed in shallow holes of about 15 cm in diameter and 50cm in depth. The optimum etching conditions, i.e., the concentration of NaOH solution, etchant temperature and etching time, are found to be 625N, $70^{circ}C$ and 5.5 hours for CR-39 detectors. A typical conversion factor of radon cup is calculated as $$1track/mm^3{cdot}30day=0.059Bq/{ell}$$. Average radon concentrations over 30 days measured in Cheju Island from May 1, 1987 to April 23, 1988 are $3.1{pm}0.3Bq/{ell}$ for open radon cups and $1.7{pm}0.2Bq/{ell}$ for closed radon cups.
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