Implementation of the kinetics in the three-dimensional transport code Aztran

In this research, the time dependent neutron transport equation is solved numerically in XYZ geometry for several energy groups using the discrete ordinates method Sn for the discretization of the angular variable, the nodal method RTN-0 for the spatial discretization, and the θ method for the discretization in time. To accomplish this, the starting point was the AZTRAN code, which is part of the AZTLAN platform, the project has been assigned with the number 212602, Plataforma Mexicana para el Analisis y Diseno de Reactores Nucleares, financed by the CONACYT-SENER-SUSTENTABILIDAD ENERGETICA funds. At first, the AZTRAN code only solved the neutron transport equation in stationary state, for which the temporal part was implemented. This was accomplished by integrating the time dependent neutron transport equation and the corresponding balance equations for the concentration of delayed neutron precursors, for which the θ method was applied. After directly implementing the kinetic to AZTRAN and being sure regarding its capacity to simulate several test problems, an improved quasi-static methodology was implemented, which is a technique to reduce the computing time where the angular flux is factorized by the product of two functions called shape and amplitude, where the shape function is used for long time lapses, named macro-steps, and the amplitude function for short time lapses, named micro-steps. The new AZTRAN version is written in FORTRAN 95 and several benchmark problems were simulated and taken from literature. The engaged benchmark problems were of one, two, and three dimensions which allowed to corroborate the precision and stability of the AZTRAN code, proving in general, in all tests of reference, a good behavior. (author)