Adaptive energy mesh constructor for multigroup libraries of the deterministic transport code APOLLO2

The multigroup solution of the neutron transport equation needs appropriate energy discretized cross sections. Nowadays, the errors of multigroup libraries can only be evaluated at the end of the calculation, by comparison with Monte Carlo results. In this work, we develop an adaptive energy mesh constructor (AEMC) that defines a multigroup mesh for predefined requisites of precision and calculation time. AEMC works with a finite number of groups and searches the optimal bounds of a fine reference mesh that minimize the errors of the multigroup transport solutions for a predefined set of infinite medium problems. The new methodology enabled to define a 1499 group mesh for fast sodium reactor applications. Homogeneous tests at different void fractions and a simplified 1D transport calculation show the similar precision of the new mesh to the well validated 1968 ECCO mesh. (authors)