Final Report for the FUMEX-III Exercise with the TRANSURANUS Code

This report describes the results of the fourth round robin exercise organized by the IAEA for the LWR fuel behaviour codes. The previous exercise was organized by the IAEA in 2002-2007. ITU contributed to the IAEA FUMEX- II co-ordinated research project (CRP) by: - The development of a high burn-up TRANSURANUS-WWER Version - Verification of the TRANSURANUS-WWER Version for WWER-1000 reactors - Further verification of the TRANSURANUS Code by selected irradiations from the IFPE Database - Transfer of latest ITU knowledge in the following areas: high burnup effects and MOX behaviour as far as confidentiality is not concerned. Within the FUMEX-III project this work continues by: - Knowledge transfer and release of the TRANSURANUS code to safety authorities in several neighbouring countries of the European Union - Further verification of the TRANSURANUS Code by selected irradiations from the IFPE Database: extending the verification of the TRANSURANUS code on the basis of the cases related to the behaviour of high burnup UO2 fuel, Gd-containing UO2 fuel and MOX fuel under normal operating conditions in LWRs, including WWER. The simulation of the pellet-cladding mechanical interaction received particular attention. - Extending the TRANSURANUS code for simulation of fuel rods under accidental conditions, such as a loss of coolant accidents (LOCA) and a Reactivity Initiated Accident (RIA), for which various code improvements have been implemented and other changes are still under development. During the entire period of the CRP, ITU has carried out all priority cases, except for IFA-519 for which insufficient data have been provided. All these results are considered in this report. However, in order to limit the redundancy of work of various TRANSURANUS users involved in the FUMEX-III CRP, ITU has co-ordinated part of the work of the partners in Bulgaria, Romania and Italy. More precisely, the work on the WWER version of the code has been carried out in collaboration with INRNE in Bulgaria, the CANDU cases were performed in close collaboration with INR in Romania, and some MOX cases as well as RIA cases in collaboration with POLIMI and ENEA in Italy. Each group has tested complementary parameters and models developed by themselves and implemented in the TRANSURANUS code. The results obtained by the various groups are compiled in independent reports and will be referred to where appropriate for the sake of conciseness. The results were (partially) discussed during a specific session dedicated to FUMEX-III at the workshop ''Towards nuclear fuel modelling in the various reactor types across Europe with TRANSURANUS'' held in September 2009 in Burgas. ITU organised this international workshop in connection with the WWER fuel performance meeting in Burgas (Bulgaria), in order to promote the corresponding research and development activities of the FUMEX-III CRP. Finally, the results were also presented and discussed during the most recent WWER fuel performance meeting in Burgas. (author)