LAFARA: a new underground laboratory in the French Pyrenees for ultra low-level gamma-ray spectrometry

We describe a new underground laboratory, namely LAFARA (for LAboratoire de mesure des FAibles RAdioactivites), that was recently created in the French Pyrenees. This laboratory is primarily designed to analyze environmental samples that display low radioactivity levels using gamma-ray spectrometry. Two high-purity germanium detectors were placed under 85 m of rock (ca. 215 m water equivalent) in the tunnel of Ferrieres (Ariege, France). The background is thus reduced by a factor of 20 in comparison to above-ground laboratories. Both detectors are fully equipped so that the samples can be analyzed in an automatic mode without requiring permanent presence of a technician in the laboratory. Auto-samplers (twenty positions) and systems to fill liquid nitrogen automatically provide one month of autonomy to the spectrometers. The LAFARA facility allows us to develop new applications in the field of environmental sciences based on the use of natural radionuclides present at low levels in the environment. As an illustration, we present two of these applications: i) dating of marine sediments using the decay of Ra-226 in sedimentary barite (BaSO4), ii) determination of Ac-227 (Pa-231) activities in marine sediment cores. (C) 2012 Elsevier Ltd. All rights reserved.