Adaptive matrix formation (AMF) method of space-time multigroup reactor kinetics equations in multidimensional model

Adaptive matrix formation (AMF) method has been developed for the numerical solution of the transient multigroup neutron diffusion and delayed precursor equations in two- and three-dimensional geometry. The method is applied to a general class of two- and three- dimensional problems. The results of numerical experiments, as well as comparison with space-time experimental results indicate that the method is accurate and that the two- and three-dimensional calculations can be performed at “reasonable” computer costs. Moreover, the AMF method offers the flexibility of using smaller time steps between flux shape calculations to achieve a specified accuracy and capability, without encountering numerical problems that occur in the other conventional methods. There is a large considerable saving in computer time and costs due to the partitioning of the matrix adopted in the presented AMF method. The two- and three-dimensional problems were analyzed with the present calculations model to illustrate the accuracy and stability of the method. Furthermore, the stability of the investigated method has been tested for sinusoidal, ramp, and step-change reactivity insertions. The results are in a good agreement with those of the other less approximate methods, including the problems in which the reflector zone is perturbed.