Simulation of a radiotracer experiment by flow and detection chain modelling: A first step towards better interpretation

This document presents the work done by the French team in the framework of the IAEA Research Coordination Programme. A 'thought experiment', consisting in an ideal γ-emitting tracer injection in laminar backward-facing step flow, was modelled. This included calculation of the flow and concentration fields by CFD, and calculation of detector response thanks to a Monte-Carlo code. The objective was twofold: show the influence of tracer energy on detector response in flow with a recirculation; set the foundations for (hopefully) better interpretation of data from a radioactive tracer experiment. The results are consistent with expectations. An attempt is made at determining the characteristics of the internal flow by exploiting the calculated tracer response curves with the usual tools for tracer data analysis. Limited success is achieved which shows the need for more work to reach the prescribed goal. A few proposals are made for improving the data treatment procedure. (author)