Modeling Szilard-Chalmers reactions 

For most nuclear medical purposes, radionuclides need to have a high specific activity. To be able to reach this high specific activity, it is necessary to separate the produced radionuclides from the target material after irradiation. However, in a nuclear reactor most production reactions are (n,y), which means that the produced isotope is the same element as the target material. This makes chemical separation rather difficult. Another way to isolate the produced radionuclides is using the Szilard-Chalmers method. This means that if your target atom is bound to a molecule and subsequently absorbs a neutron, a number of prompt-gamma’s are emitted. If these prompt-gamma’s have a high enough energy, the produced radionuclide receives a recoil energy which can be enough to break chemical bonds. This would make the produced radionuclide chemically different from the target molecule, and therefore separable.However, it turns out not to be so easy to determine the chance that a produced radionuclide has a high enough recoil energy to break these bonds. This is because there are different energy levels from which different prompt gamma cascades are possible, containing prompt gamma’s with both high and low energies, which in some cases are emitted almost simultaneously (in under different angles, but non-isotropically).In this project, we want to model this proces using Monte Carlo programming, and in this way be able to predict what the chance is that a certain produced radionuclide through (n,y) reactions receives enough recoil energy to break free from the target molecule. Subsequently, we will perform irradiations of different target materials in our nuclear reactor to experimentally validate the model. In the end, the developed model will help immensely in determining which radionuclides can benefit from this production method.