Radon anomalies: the SDNT method provides more reliable results

Radon is a radioactive gas present everywhere in the earth's crust. As one of the various natural gaseous tracers, it is widely used in different earth sciences (geological prospecting, investigation of faults, vulcanology and seismology, and so on). In the case of hydro-geological prospecting, radon can reveal permeable discontinuities in the earth related to the presence of radium 226 carried by ground water. In a collaborative project involving the Geotherma company and the university of Franche-Comte, this tracer has been used in the search for new thermal springs. Two techniques developed at the university of Franche-Comte have been used to measure radon concentrations in the earth and in water. These measuring techniques provide either instantaneous results, using a proportional counter, or integrated data by using solid nuclear path detectors. The complementary results obtained make it possible to map the radon emanations on the site being investigated. By processing the results as a function of the site characteristics it is precisely to locate surface anomalies, which may be related either to the underlying geology or to the presence of a nearby underground fluid (which may be gaseous or liquid) carrying the gas to the surface. (authors). 3 refs., 3 figs