Determination of bulk radon emanation rates by high resolution gamma-ray spectroscopy

In the present study, a new modified technique of gamma-ray spectroscopy was developed to quantitatively determine radon (Rn-222) emanation losses from bulk samples (size range of the order of 1 dm3) of selected granitic rocks. Accurate determination of radon loss for each bulk sample is obtained by comparing apparent U-238 abundances calculated from activities of radon precursors (Th-234 and Ra-226) with those calculated from radon progeny (Pb-214 and Bi-214). Activities of these precursor and progeny nuclides were found from the gamma-ray spectra of the nuclides collected by a high resolution-high efficiency reverse electrode germanium (REGe) crystal gamma-ray detector equipped with a 8192 channel multichannel analyzer. This arrangement allowed precise and simultaneous acquisition of the desired gamma-ray spectra from bulk solids without the need for special preparation of samples. The present study was undertaken for several reasons. One of the authors' objectives was to accurately measure U and Th abundances in bulk samples by properly calibrating our equipment. Secondly, they hoped to develop an analytical procedure for determining bulk radon losses from solids, and finally, they sought to relate the data to predictive models for radon losses based on alpha-recoil and diffusion theories. These objectives were attempted on bulk solids using a wide range and a variety of solid samples