Report issued by the Argonne National Laboratory discussing a computer program used for fast reactor safety experiments. As stated in the summary, "this report gives a detailed description of a hybrid-computer program for calculating temperatures in a multi-region, axisymmetric, cylindrical configuration consisting of solid materials bounded by flowing coolant. Included is an explanation of the mathematical methods, together with a discussion of special features, input-output descriptions, and several sample problems" (p. 7). This report includes tables, and illustrations.