OpenMC - TD, A New Module for Monte Carlo Time Dependent Simulations Used to Simulate a CANDU-6 Cell LOCA Accident

Abstract

The solution of the time dependent Boltzmann equation remains quite a challenge. For transient problems, the two steps approach is still used, with the nuclear reactor data obtained using an adiabatic assumption, whereby perturbed cross-sections are calculated from static computations.We developed a new method using the stochastic Monte Carlo approach to solve the time dependent transport equation. There are two reasons for this choice. First, at the cell level, we will be able to obtain time dependent homogenized cross sections for use in full core diffusion calculations. Second, the Monte Carlo methods are scalable to perform full core if and when appropriate computer resources become available.The OpenMC code developed at MIT was used as the initial platform for our work, by adding time dependent modules. A particular attention was given to the treatment of delayed neutrons during the simulation.Our results show that the adiabatic assumption for cross sectionsshould be reviewed and the time dependent Monte Carlo method is a significant alternative for the solution of time dependent neutron transport problems.