BURNCAL is a Fortran computer code designed to aid in analysis, prediction, and optimization of fuel burnup performance in a nuclear reactor. The code uses output parameters generated by the Monte Carlo neutronics code MCNP to determine the isotopic inventory as a function of time and power density. The code allows for multiple fueled regions to be analyzed. The companion code, RELOAD, can be used to shuffle fueled regions or reload regions with fresh fuel. BURNCAL can be used to study the reactivity effects and isotopic inventory as a function of time for a nuclear reactor system. Neutron transmutation, fission, and radioactive decay are included in the modeling of the production and removal terms for each isotope of interest. For a fueled region, neutron transmutation, fuel depletion, fission-product poisoning, actinide generation, and burnable poison loading and depletion effects are included in the calculation. Fueled and un-fueled regions, such as cladding and moderator, can be analyzed simultaneously. The nuclides analyzed are limited only by the neutron cross section availability in the MCNP cross-section library. BURNCAL is unique in comparison to other burnup codes in that it does not use the calculated neutron flux as input to other computer codes to generate the nuclide mixture for the next time step. Instead, BURNCAL directly uses the neutron absorption tally/reaction information generated by MCNP for each nuclide of interest to determine the nuclide inventory for that region. This allows for the full capabilities of MCNP to be incorporated into the calculation and a more accurate and robust analysis to be performed.
EXECUTIVE SUMMARYThere are many coupled neutronic/isotope-composition codes available to the nuclear community that are capable of performing burnup and depletion calculations on nuclear reactor fuels or fuel element assemblies. In general, these coupled codes all work in a similar fashion -a neutronics code performs a calculation to determine the multiplication factor, k eff , and the energy dependent neutron flux for a given geometry and fuel loading; another code then uses the neutron flux, power density, and material composition to determine the new material composition after a given burnup time. The material composition can include transmuted isotopes, fission products, actinides, and burnable poisons, as well as the fissile component of the fuel. Many of these codes have been used extensively by the nuclear industry, perform adequately, and give perfectly acceptable answers for their intended purpose. However, using a neutronics code such as MCNP to directly determine the neutron absorption rate for each individual nuclide as part of the neutronics calculation, thereby eliminating the need to include neutron flux information in the burnup calculation, is a more straightforward and accurate solution method. To the author's knowledge, applying this type of a methodology on a modern neutronics analysis code has never been accomplished. The goal of this work was to develop a ...