Uncertainties of Source Term Assessments (USTA): An Indispensable Project

The USTA (Uncertainties of Source Term Assessments) project, coordinated by CIEMAT, was submitted to the most recent H2020 call concerning nuclear fission and it has been evaluated and considered within a reserve list (i.e., subject to funds availability once the approved projects negociation is finished). The main objective of the project is to determine the current accident analysis codes predictability of the radioactive source term released to the environment during an NPP severe accident. Through setting a well-balanced structure, USTA will identify and quantify key processes/phenomena affecting the source term and their associated uncertainties; evaluate applicable methods of uncertainty analysis in the field of severe accidents; quantify the source term uncertainty linked to the most risk-significant severe accidents for the main NPP designs and analysis codes; define best practices, approaches and recommendations for ST uncertainty analyses; and eventually highlight research issues worth to be investigated to largely reduce the major uncertainties found. In short, the project will provide a clear statement of where the Nuclear Safety Community actually is in the area of Source Term modelling and how to effectively reduce the remaining uncertainties. USTA would be the first European project ever conducted on the application of the Best Estimate Plus Uncertainty approach in deterministic safety analysis focused on the source term. More than 30 organizations credited in the field of severe accidents are involved, from utilities, TSOs, National Labs and academia, including 7 institutions from America and Asia.