Simulation of CANDU reactor transients using hierarchical super nodal analysis

In order to reduce the computing costs of the time-dependent diffusion calculations without introducing unacceptable inaccuracies in the solution, a hierarchical space-time kinetics procedure which is a combination of NET (Nodal Equivalence Theory) and QS (Quasi-Static method) is being developed. The time scales are divided into a three level hierarchy. On the smaller time step, the point kinetics equations are solved. At intermediate time steps, a coarse representation of the reactor core is solved using NET Finally, full fine mesh calculations are performed over a large time scale. This scheme appears to have the potential of simulating demanding transients with lower computational cost than conventional methods. Detailed investigations are being carried out to reproduce the total power and flux distribution in coarse level calculations. (author)