Two Methods of Calculating Fast Reactor Control Rod Effect and Their Agreement With Experiment

The effect of control rod movement in a fast reactor has been calculated directly by solving a series of two-dimensional multigroup problems and indirectly by using a set of danger coefficients derived from one-dimensional calculations. The values of reactivity insertion calculated by the two methods for complete safety rod withdrawal agree within three percent. The shape of a curve of relative reactivity insertion vs. rod withdrawal distance is also predicted, with good agreement between the two methods. Differences between the two predictions are within three percent of the maximum value. Comparison of these predictions with a set of normalized experimental values shows agreement within four percent of the maximum value.