In-line (α,n) source sampling methodology for Monte Carlo radiation transport simulations

A new in-line method for sampling neutrons emitted in (α,n) reactions based on alpha particle source information has been developed for continuous-energy Monte Carlo simulations. The new method uses a continuous-slowing-down model coupled with (α,n) cross section data to pre-compute the expected neutron yield over the alpha particle lifetime. This eliminates the complexity and computational cost associated with explicit charged particle transport. When combined with an integrated alpha particle decay source sampling capability, the proposed method provides an efficient and accurate method for sampling (α,n) neutrons based solely on nuclide inventories in the problem, with no additional user input required. Results from several example calculations show that the proposed method reproduces the (α,n) neutron yields and energy spectra from reference experiments and calculations. (authors)