It is essential to calculate the structural integrity of reactor components with a high degree of accuracy in order to make correct decisions regarding plant lifetime at the design stage, safety margins and potential plant life extensions. The OECD Nuclear Energy Agency (NEA) is therefore organising a series of benchmarks to verify the current international level of accuracy in pressure vessel fluence calculations and to clarify the relative merits of various methodologies. By extension, this enables the identification of areas for possible improvements in the various calculation schemes.
As a follow-up to the previous UO2-fuelled VENUS-1 two-dimensional (2-D) and VENUS-3 three-dimensional (3-D) benchmarks, and given that many commercial nuclear power plants in Europe and in Japan use MOX fuel and that the use of MOX fuel in LWRs presents different neutron characteristics, the present benchmark was launched in 2004 using the measured data of the VENUS-2 MOX-fuelled critical experiments. This report provides an analysis of the results supplied by 12 participants from 7 countries. The results have revealed that the computer codes and nuclear data currently used for MOX-fuelled systems in OECD/NEA member countries appear able to produce results with a sufficiently high level of accuracy in dosimetry calculations. This report will be of particular interest not only to reactor physicists and nuclear data evaluators, but also to nuclear utilities.