Application of a LaBr₃(Ce) Scintillation Detector to an Environmental Radiation Monitor

Abstract

To simultaneously determine the dose rate and radioactivity for detected gamma nuclides from one measured energy spectrum, the dose rate spectroscopy using a LaBr3(Ce) scintillation detector was first applied to an environmental radiation monitor, installed in the relative flat land at a height of about 1 m above the ground. After subtracting the intrinsic background of the LaBr3(Ce) detector used in the measured energy spectrum for count rate, that spectrum was converted into one for dose rate using the dose conversion factor. Several full-energy absorption peaks were then analyzed to calculate the individual dose rate for detected gamma nuclides, such as <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">214</sup> Pb, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">214</sup> Bi, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">228</sup> Ac, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">212</sup> Pb, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">208</sup> Tl, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sup> K. The radioactivity of these nuclides distributed in the ground was calculated from their individual dose rates and conversion coefficients of the dose rate at 1 m above the ground into the radioactivity in the ground. The experimental verification was finally conducted by comparing the results of radioactivity using a portable high purity Ge (HPGe) detector and a LaBr3(Ce) detector equipped with the in situ objective counting system method and dose rate spectroscopy, respectively. Below, a 20% difference between two methods was shown in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">214</sup> Bi, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">228</sup> Ac, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">208</sup> Tl, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40</sup> K. In the case of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">214</sup> Pb and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">212</sup> Pb with low-energy photons, the calculated radioactivity using a LaBr3(Ce) detector was also within a 30% difference from those of an HPGe detector.