In Europe, the two main nuclear accident response decision support systems in use are ARGOS and JRODOS, both of which make use of the FDMT (Food Chain and Dose Module for Terrestrial pathways) model to simulate the transfer of radioactivity along terrestrial food chains and to predict radionuclide activity concentrations in human foodstuffs. FDMT was originally developed in the early 1990s for Southern German agricultural conditions. Its application to other geographical settings has raised concerns regarding its fitness for purpose. Furthermore, the FDMT model in its original format lacks transparency, flexibility, and the possibility to be run probabilistically. In order to improve FDMT’s fitness for purpose and overcome its main shortcomings, it has been implemented in a new modelling platform which incorporates powerful numerical solvers and renders uncertainty and sensitivity analysis possible. The modelling structure of FDMT has been re-configured, and a library configuration has been introduced which offers flexibility in working such that model components can be tested, modified, or replaced easily. The new FDMT allows for the consideration of case/region-specific issues and to make predictions which are of more relevance and of better use with regard to decision making and management of risk. Furthermore, the default databases of FDMT have been updated and wherever possible PDFs have been assigned. In this paper, the transition of FDMT from an old to a new modelling structure is presented along with a demonstration of developments achieved.