Source term computation with ASTEC code

The ASTEC integral code is jointly developed by IRSN (Institut de Radioprotection et de Surete Nucleaire, France) and GRS (Gesellschaft fuer anlagen und Reaktor Sicherheit, Germany). The aim of this code is to compute the progression of severe accidents and the release of fission products into the environment (the source term) on nuclear power plants, covering all important in-vessel and ex-vessel phenomena. An example of source term evaluation with the current reference version ASTEC V2.0 is presented for a complete accident scenario of several days on a model reactor close to the French PWR 1300 MWe.The selected scenario is the loss of feed-water of steam generator, called H2 accident sequence with venting of the containment (French U5 ultimate venting procedure). Results of this computation with ASTEC V2.0 is compared to results obtained using an advanced version of ASTEC including improved models of heterogeneous chemistry for the fission products in the containment. This highlights the capitalization in ASTEC of the state of the art of the research on source term modelling. (authors)