Extension and validation of the TRANSURANUS code in the course of the ESSANUF project

The main objective of the EU funded project ESSANUF is to contribute to the security of nuclear fuel supply by developing an alternative nuclear fuel design, as well as licensing methods and methodologies, for the Russian designed pressurized water reactor VVER-440 operated in the EU and neighbouring countries. The TRANSURANUS fuel rod performance code has been selected for the fuel rod design analyses as well as for the design basis accident (DBA) analyses. To this end, specific material properties for fuel and cladding have been implemented, and new generic models for inner cladding oxidation, breakaway oxidation and hydrogen uptake have been developed. Moreover, the capabilities of the TRANSURANUS code for probabilistic analyses by Monte-Carlo have been extended to cover fission gas behaviour in the fuel and oxidation rates of the cladding. A first series of validation computations has been made. While focusing on normal operation irradiation experiments at the OECD Halden Reactor, they also include a comparison to cladding burst and high-temperature oxidation data obtained under DBA conditions. The experimental data are compared to the simulations by TRANSURANUS applying both best-estimate as well as conservative models. A first analysis is made by means of descriptive statistics.