Development of methods for in situ measurements of radioactivity in the enviroment

Abstract: In case of a release of radioactive nuclides into the environment it is necessary to have reliable methods to estimate the potential effect on population and ecosystem. In this context the total activity deposited, the elemental composition and its depth distribution are of importance.An efficient in situ method to estimate the average contamination over larger areas (typically ?1000 m^2) using high purity germanium (HPGe) detectors has been developed. The method combines simulation of photon transport with measured detector properties. Comparisons regarding the total activity of Cs-137 determined from gamma spectra recorded in situ to results from soil sampling are presented.Ground properties, topography and the process of deposition of anthropogenic radionuclides can lead to large fluctuations even over small distances. Large volume cadmium telluride (CdTe) detectors are interesting candidates for local (<1 m^2) in situ measurements but are hampered by poor charge collection. The possibility to improve the energy resolution for planar and hemispheric CdTe detectors has been investigated along with laboratory experiments investigating the possibility to determine the activity of a buried radioactive source. Results derived using a standard sodium iodide detector are presented as a comparison.