Abstract In this paper, time dependent neutron transport in fissionable media is simulated by Monte Carlo method, and the neutronic parameters are estimated. In this article, the effective multiplication factor, neutron lifetime, and flux distribution in steady state condition are calculated. The comparison of the results obtained by this method, with those of the experimental measurements and the other calculations have shown that they are in very good agreement.

Abstract Storage of high-level waste and spent fuels from nuclear reactors is a main concern in the field of nuclear engineering. Generally, deep geological repository is suggested for this purpose. Heat transfer by high-level waste and spent fuels and their impacts on environment in a deep geological repository is an important subject for study. In this paper a three dimentional model for heat transfer in canisters and a deep tunnel was developed. FLUENT 6.0 with K-ε turbulence model was used to simulate the turbulent flow with and without radiation. The influence of parameters such as heat flux, air velocity, and depth of tunnel and the ground and canisters surface temperature were studied for two cases of forced and natural convection. For the air velocity of 0.6m/s with 67 canisters in the tunnel and 360kW/m² the initial heat flux for each canister, it is shown that the surface temperature reaches its allowed maximum limit of 93^oC for concrete.