SPALLDKZ : a nuclear decay model

Currently research is being conducted at accelerator facilities, such as the Holifield Radioactive Ion Beam Facility at the Oak Ridge National Laboratory, that is key in efforts to understand nuclear structure. Targets bombarded with high-energy particles fragment into a wide assortment of radioactive nuclides. These radioactive nuclides are then collected and used in further experimentation as Radioactive Ion Beams (RIBs). To optimize current research, accurate predictions of the products of spallation reactions are needed as well as an understanding of the longevity of these radionuclides. This work describes a numerically based nuclear decay model for predicting the time-development of spallation yields for accelerator applications (in particular RIB applications). No other loss terms (i.e. diffusion from target) accompany the time-decay in the model. The model is implemented in the computer code Spallation Decays (SPALLDKZ) which is used to predict time-dependent radionuclide amounts in accelerator targets for a feasibility study for RIB applications. SPALLDKZ uses a numerical process which solves first order differential equations over many time steps, and is not limited by the number of nuclides for which the calculations are to be made. Estimates of decay constants for exotic nuclides extending toward the neutron and proton drip lines are made to include all predicted spallation yields in the decay calculations. Results from SPALLDKZ are compared to those from another decay code, ORIHET, to help determine the effectiveness of SPALLDKZ. This is done using spallation yields from aluminum and uranium (U-238) targets. The overall results show a good correlation between the output of the two codes.