Physics Assessment of Energy Deposition Distribution in Pressure-Tube Heavy Water Reactor Lattices with Uranium-Based and Thorium-Based Fuels

摘要

Lattice physics studies have been carried out with MCNP to evaluate the energy deposition distribution in three types of PT-HWR lattices containing uranium-based and thorium-based fuels at different stages of burnup. Results show that between 95.4% and 97.1% of the energy from neutrons (including fission) and prompt gammas are deposited in the fuel channel, which includes the fuel pellets, clad, displacer rods (where applicable), coolant and pressure tube. Between 2.9% and 4.6% of the energy is deposited in the moderator and calandria tube. As burnup proceeds and fissile fuel is depleted, a larger fraction of the energy is deposited in the moderator+CT. The ratio of total energy deposition in the lattice to that in the fuel channel for mid-burnup fuel ranges between 1.037 and 1.040, depending on the lattice concept, and the results are comparable to the ratio used in previous core physics smdies (1.047), with the small difference being largely attributed to the delayed energy deposition from decay of fission products in the previous work. These results give confidence in the core physics analyses performed to date.