Radon exhalation from uranium mill tailings: experimental validation of a 1-D model .

Ferry, C; Richon, P; Beneito, A; Robe, MC. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY, 54 (1) 99-108; 2001 également présenté à Rio de Janeiro (Brazil) 12-17 Sep 1999. International symposium on technologically enhanced natural radiation. Book of Abstracts 1999 124 p. p. 32

TRACI, a model based on the physical mechanisms governing the radon transport in unsaturated soils, has been developed to evaluate the radon flux density at Uranium Mill Tailings (UMT) covers surface. First, moisture contents in the soil, induced by weather conditions, are calculated. Then, radon concentrations in the air-filled pore space, and radon flux density at the soil surface, are deduced from a transport model that takes account for diffusion and convection in the pore space. To check the hypothesis used in TRACI and the efficiency of cover layers, an in situ study was launched in 1997 with the French uranium mining company, COGEMA. It consists of continuous measurements of moisture contents, suctions, radon concentrations at various depths inside an UMT cover, and flux density at its surface. The first analysis made on in-situ observations shows that radon concentrations and flux density, calculated with a steady-state diffusion model using monthly averaged moisture contents, are in good agreement with monthly averaged concentrations and flux density measured.