Reference 2D and 3D Monte Carlo calculations of idealized cases of a heavy water reactor for benchmark comparison with results from deterministic methods

For the benchmark problems proposed in the revision of the reactor physics programs and models used for heavy water power plants, based on Atucha-I plant, it was considered convenient to include comparisons with Monte Carlo calculations. Some two and three dimensional core benchmark problems based on idealized conditions were defined including small adjustments to improve the speed of the calculation and 1/12 and 1/6 symmetry. This report presents a brief description of the Monte Carlo code and options used for these calculations, a description of the cases, and the results of the benchmark core calculations using MCNP5. Results of these Monte Carlo calculations are presented to be used as reference calculations for comparisons with values obtained with deterministic codes (presented elsewhere on this Meeting). The everyday improvement of hardware installation has made possible 2D and 3D flux and power distribution calculation of nuclear reactors in an acceptable amount of time by means of Monte Carlo method. Results obtained using this method can be considered as equivalent to an exact resolution of the Boltzmann Transport Equation for a spatial representation with all the necessary detail. A detailed study about the optimal number of histories needed for achieving a good precision has also been performed.. This is the reason why these results can be considered as benchmark cases for the validation of other methods. (author)