Expanding alpha self-attenuation simulation by radioisotope dioxides

The relative self-attenuation effect for different radionuclides were simulated to calculate the average yield and average energy thereof like the previous into AmO2 particulates. These include Americium-241, Neptunium-237, and Uranium-234, 235, and 238. Plutonium-240 was also an intended nuclide of interest but could not be simulated; attempts were met with a segmentation fault, and a cursory check on the devlopment forums indicated that Plutonium is not a generally available material in the code. The alpha energies used were those characteristic of the highest yield per decay of each radionuclide.

The average yield is shown in Figure 1, with the former zoomed into the first five microns. The relative difference between each nuclide particulate yield is initially negligible until 1.5-2 microns. The largest differences occur around 3 microns then they gradually decrease through 5 microns. The order of decreasing alpha yield across all particle sizes are Am-241, U-234, U-235, Np-237, then U-238 oxide. This order corresponds to a decreasing initial alpha energy with the exception of 235UO2 above 237NpO2. This may indicate a marginally higher alpha cross-section for Neptunium to yield unexpectedly fewer at that energy.

The alpha energy loss is shown in Figure 2, with the former zoomed into the first five microns. The relative difference between each nuclide’s average exiting energy varies initially through 3-4 microns, afterwards they asymptotically approach respective limits, gradually solidifying relative differences. The initial variation shows fluctuation and cross-overs of U-234, U-235, and Np-237 alphas, whereas Am-241 and U-238 alphas consistently have highest and lowest exiting energies respectively.