Neutron fluence, dosimetry and damage response determination in in-core/ex-core components of the venus CEN/SCK LWR using 3-D Monte Carlo simulations: NEA's VENUS-3 benchmark

Validating state-of-the-art methods used to predict fluence exposure to rea ctor pressure vessels (RPVs) has become an important issue in identifying t he sources of uncertainty in the estimated RPV fluence for pressurized wate r reactors. This is a very important aspect in evaluating irradiation damag e leading to the hardening and embrittlement of such structural components. One of the major benchmark experiments carried out to test three-dimension al methodologies is the VENUS-3 Benchmark Experiment in which three-dimensi onal Monte Carlo and S-n codes have proved more efficient than synthesis me thods. At the Instituto de Fusion Nuclear (DENIM) at the Universidad Polite cnica de Madrid, a detailed full three-dimensional model of the Venus Criti cal Facility has been developed making use of the Monte Carlo transport cod e MCNP4B. The problem geometry and source modeling are described, and resul ts, including calculated versus experimental (C/E) ratios as well as additi onal studies, are presented. Evidence was found that the great majority of C/E values fell within the 10% tolerance and most within 5%. Tolerance limi ts are discussed on the basis of evaluated data library and fission spectra sensitivity, where a value ranging between 10 to 15% should be accepted. A lso, a calculation of the atomic displacement rate has been carried out in various locations throughout the reactor,finding that values of 0.0001 disp lacements per atom in external components such as the core barrel are repre sentative of this type of reactor during a 30-yr time span.