Beta spectrometry for environmental radioactivity measurements

Abstract

Various anthropogenic sources contribute to the inventory of long lived beta emitters in the environment (40K, 210 Pb, ^Co, l37 Cs, 90 Y). Studies have been carried out to obtain the 90 Sr distribution in environment in order to estimate its impact in terms of radiation exposure to humans. It is routinely measured it by proportional counter after radiochemistry. An incomplete radiochemical separation leads to a deposit submitted to count polluted by natural beta emitters. In order to guarantee results, 90 Y daughter of 90 Sr, is systematicall y extracted from the final radiochemical fraction and counted. The ^Y decreasing (T, n = 2.67 days) is checked by 2 hours successive counts during 64 hours. The delay between the end of radiochemistr y and the counting is 15 days imposed for the radioactive equilibrium between 90 Sr and 90 Y to be reached. The duration from the beginning of the radiochemistry to the result of the measurement is of the order of five weeks. In order to diminish this procedure, and in order to detect several radionuclides simultaneously, we study the possibility of a beta spectrometer based on two PIPS (Planar Passivated Implanted Silicon © Canberra) solid detectors. Because of their different p,^ energies and to their spectral features (continuum shape, conversion electrons), we have shown that the main radionuclides like