Transient Fission Matrix: Kinetic calculation and kinetic parameters βeff and Λeff calculation

Abstract In this paper, we present a time dependent version of the fission matrix method called Transient Fission Matrix (TFM) that we developed to perform accurate spatial kinetic calculations with a reduced computational cost. The matrices are generated once using the Monte Carlo neutron transport MCNP prior to the kinetic calculations. This article is devoted to the description of this approach with two different sets of equations depending on the aimed precision. We tested the TFM approach in several instances. In the calculation of the kinetic parameters such as β eff and Λ eff on the Flattop and Jezebel experiments, the results obtained are compatible with adjoint weighted calculations performed with the Monte Carlo neutron transport code SERPENT. Likewise, our calculated value of the α Rossi observable is also compatible with the experimental measurement. Finally a time–space prompt neutron propagation induced by a neutron pulse on Flattop has been calculated using the TFM approach and compared to a reference time dependent SERPENT calculation. Again, the results obtained demonstrate the good characterization of the time–space system response by the TFM approach.