On the simulation of neutron noise using a discrete ordinates method

The method of discrete ordinates is investigated for neutron noise simulations in the frequency domain. For this purpose, solver NOISE-SN developed and used to simulate two problems that are respectively derived from two-dimensional systems described transport simulation benchmarks C4V C5G7. In first problem based on system, compared diffusion-based simulator CORE SIM+. These results show SIM+ calculate similar spatial distributions noise, although significant differences can be found at location perturbation locations with strong variations material properties, where expected more accurate than diffusion theory. Then calculations performed test different SN approximations, fictitious source may applied mitigate possible numerical artifacts, known as ray effect. second C5G7 choice a low order leads unphysical values because increase or introducing equations solved alleviates issue. option shown remove effect without high thus too expensive calculations, even though strength needs tuned carefully avoid very slow convergence rates.