Dominance Ratio Assessment and Monte Carlo Criticality Simulations: Dealing with High Dominance Ratio Systems

Burnup instabilities in the full-core HTR model simulation

“…The phenomenon of spatial oscillations can be described as a strong coupling between neutron flux and nuclide field. It has been observed for the systems of a large spatial size and high dominance ratio (Dumonteil and Courau, 2010). Also, a conditional stability of the time step methodology was indicated as a potentially weak point of the simulation.…”

“…We observed the presence of burnup oscillations after about 1000 EFPD of simulation, what suggests, that system model becomes unstable for burnup procedure after some depletion-related evolution. The origin of this behavior is spectral and spatial change of neutron flux during fuel irradiation and most probably increase of system's dominance ratioexplained by (Dumonteil and Courau, 2010).…”

“…On the other hand, spatially isolated burnable zones exhibit weak neutron coupling, so large nuclear systems can be basically prone to the instabilities (in the contrary to the fast systems, which are usually compact), analyzed by (Dumonteil and Courau, 2010). Fortunately, many thermal reactors usually comprise some geometrical symmetry, that permits ones to reduce the size of the model and number of fuel zones.…”

Calculating Alpha Eigenvalues and Eigenfunctions with a Markov Transition Rate Matrix Monte Carlo Method

“…Currently, the direct core-to-storage fuel cycle has commercial light water reactors (LWR) producing waste requiring storage for at least several hundred years. A more complete fuel cycle reduces this storage time by transmuting actinides in spent fuel with fast reactors or ADS, with the latter having some neutronic advantages [30].…”

Multiscale Kinetic Transport

“…In the area of kinetic transport, multiscale problems are common in micro-and nanoscale gas dynamics [1], plasma physics [2], micro-and nanoscale solid-state heat transfer as mediated by phonon transport [3], electron transport [4,5] and neutron transport [6,7]. The primary challenge associated with such problems stems from the computational cost associated with capturing dynamics occurring over a wide range of scales.…”