Non invasive measurement of fused solar salts level by gamma-ray spectrometry of potassium natural radioactivity

A feasibility test, concerning a non invasive method for measuring the level of fused solar salts in a storage vessel, is described. The method is based on the spectrometry of gamma-rays emitted by the salts performed by a scintillation detector positioned outside the vessel insulation. Measurements concerned the fused solar salts (a binary mixture of NaNO(3) and KNO(3), 60%m and 40%m, respectively) contained in the Casaccia PCS experimental solar facility and working at 408 degrees C. Preliminary results demonstrated the method's feasibility by using the information from the 1.46 MeV (40)K gamma-ray line (11% branching ratio). Two deterministic models, as well as Monte Carlo simulations, were implemented for predicting the responses along the tank and specific algorithms, based on 1 or 3 detectors, were developed for the estimation of salt level.