Scintillating fibre based beta spectrometer: Proof of concept by Monte-Carlo simulation and first experimental assessment

Abstract We developed a new beta measurement method based on scintillating fibres , able to discriminate incident beta particles based on their energy, using various cladding thicknesses, which could find useful applications in the field of nuclear decommissioning and dismantling (D&D). Indeed, thanks to Monte Carlo simulations, we found that high-energy beta particles were less affected by thicker cladding than medium-energy beta particles. Therefore, combining different cladding thicknesses and a deconvolution method, we were able to identify and quantify convoluted beta spectra in a simulated scenario. In this paper, we describe the Monte Carlo simulations combined with the deconvolution algorithm based on the Maximum Likelihood-ExpectationMaximization method (ML-EM), and the associated experimental setup. We demonstrated the feasibility of such a method, using both simulated and experimental data, by deconvoluting 36Cl and 90Sr–90Y spectra, considering 36Cl as a medium-energy beta emitter and 90Sr-90Y as a high-energy beta emitter. Using fibres with only one thickness of cladding, we found that we could not estimate both contributions correctly, with errors reaching up to 71% of the actual activities. However, using two different acquisitions of fibres each one with a different cladding thickness, we were able to estimate both contributions with an error of 26% for 36Cl and 10% for 90Sr-90Y. Study of the improvement of these performances is presented and could help to fine-tune activities estimated. The next step of this work would consist in designing a beta spectrometer, based on scintillating fibres, and assess its performances. Taking advantage of both deformability capacity of scintillating fibres and their potential lengths up to a few metres, we expect that such a detection system will be well adapted to the radiological characterization of large surfaces, and suitable for deployment on uneven surfaces.