Contribution to the study of radon risk assessment - Use of Solid State Nuclear Tracks Detectors (SSNTD) for the measurement of radon in buildings

222Rn is a natural radioactive gas, originating from the decay of 226Ra. Both of these radionuclides are elements of 238U series. Uranium is naturally present in the rocks and soils, therefore radon is always present too because it is a soil gas. Radon takes the most important part in man exposure to natural sources of ionizing radiations. Moreover, it causes lung cancer. It can accumulate in confined environments such as buildings, so that its inhalation is a potential risk for human health. Thus radon measurement is necessary for radiation protection. Integrated measurement using Solid State Nuclear Tracks Detector (SSNTD) is a very common method for radon measurement in buildings because of the low cost of the detectors and their easy application. The measurement technics are based on the interaction of alpha particles emitted by radon with a polymer. Alpha particles produce in the polymer latent tracks, which need chemical revelation to be observable with optical microscopy. The number of revealed tracks is proportionnal to the average volumic activity of 222Rn corresponding to the time exposure of the detectors.The aim of this thesis work is the continuation of previous study on the preliminary investigations of radon levels in the city of Antananarivo, and to extend this study in Antsirabe, which has been shown as a region of interest. The levels of radon measured in buildings in Antananarivo and Antsirabe are typical values of indoor radon concentration. The average values of concentrations are inferior to 60 Bq.m-3. The health risk is negligible but not nul. A typical protocol of radon level measurement in Malagasy buildings is suggested to allow the implementation of a risk management policy related to radon within the Malagasy context.