Applying the TRANSURANUS Code to VVER Fuel under Accident Conditions

The TRANSURANUS code development started in 1973 and initially focused on fuel pins for fast breeder reactors. There was a shift in 1982 towards LWR applications. The VVER version of the code has been under development since the mid 90s. Specific thermal and mechanical properties for Nb-containing cladding and specific correlations for annular UO2 fuel pellets were implemented to simulate fuel rod performance under normal operating conditions. Simulation of accident conditions came to the front in the EXTRA project, which was completed in 2003. The project focused on the development of a data-base for Zr1%Nb cladding and on the elaboration of new models and correlations for plastic deformation, high-temperature oxidation and cladding failure. The new models were incorporated into the TRANSURANUS code and validated against burst tests for as-received, oxidised, and irradiated cladding specimens. Furthermore, the upgraded version of the code was applied for assessing the fulfilment of safety acceptance criteria in design basis accidents. An example for the modelling of fuel rod performance in large break LOCA is presented. In the follow-up project of EXTRA it is intended to account for the hydrogen uptake by the cladding material under accident conditions, which have detrimental effects on the mechanical properties of the cladding. New experiments concerning the oxidation kinetics, the mechanical strength and the embrittlement of hydrogen charged cladding are carried out at the AEKI (KFKI Atomic Energy Research Institute) in Hungary. The experimental program and its recent results are demonstrated. Finally, an outlook is given about the planned activities for code development. The experimental data of the new tests are to provide background for the development of new correlations and the improvement of the present models.

GYOERI Csaba;  HOZER Z.;  PEREZ-FERÓ E.;  VAN UFFELEN Paul;  SCHUBERT Arndt;  VAN DE LAAR Jacques; 

2006-01-12

International Association for Structural Mechanics in Reactor Technology (IASMiRT)

JRC31980

https://publications.jrc.ec.europa.eu/repository/handle/JRC31980,