Development of high sensitivity gamma and beta sensors for in situ diffusion tests in the mudstone in France

Overview & Synopsis

The precise monitoring of radiotracers, for example used for medical imaging, for the storage of ultimate waste, or for certain industrial applications can be a very complex subject. The development of low-noise sensors with long-term stability and high geometric flexibility were engaged by the AXINT company. (Hautefeuille, et al., 2006). My PhD thesis was focused on experiments in the diffusion of radiotracers, typically to monitor the possible leakage of radioactive products from the geological repositories. We focuses on the study of the 22Na and 36Cl ion diffusion, which is one of the highest cation and anions diffusion rate in geological medium, as well as actinides, which represent the majority of the radioactive elements of Stored nuclear waste. This thesis is in continuity with the research carried out by ANDRA (National Agency for Radioactive Waste), under contract with the laboratory ILM (Institute Light Matter), of which AXINT is the main subcontractor. The present project describes the research work that foreseen the radiation impact on the environment for the coming years during the deep disposal of nuclear waste. Our work focus on the investigation and quantification of the radionuclide diffusion through the geological clay barriers. A new in situ experiment was considered by Andra for the study of the radionuclide migration. Compared to previous experiments, this new in situ diffusion test required longer distance (hundreds of mm), longer time-scale (over 10 years), and real time in situ monitoring of radionuclides migration. To fulfill these conditions, the work was organized as following: 1: Conception and dimensional design of the Diffusion of Radio Nuclide (DRN) experiments in solving emission of beta and gamma radiations 2: Development of corresponding beta and gamma monitoring systems by means of sensors located in peripheral boreholes