The effect of control rod movement in a fast reactor was 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 per cent. The shape of a curve of relative reactivity insertion vs. rod withdrawal distance is also predicted, with agreement between the two methods. Differences between the two predictions are within three per cent of the maximum value. Comparison of these predictions with a set of normalized experimental values shows agreement within four per cent of the maximum value. (auth)
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