Summary: The use of dimensionless-parameter frequency response diagrams to determine accuracies of lumped-parameter approximations is demonstrated by two examples: calculation of the heat flux at the surface of a semi-infinite solid due to temperature fluctuations of an adjacent fluid; and the response of a counterflow heat exchanger to inlet fluid temperature perturbations. Dimensionless system parameters make it possible to use general-purpose plots to find the error in particular approximations as a function of the frequency of perturbation. Such plots are directly applicable to control-system stability problems, where the highest frequency of interest is usually apparent.

The RHOBURN program that determines various parameters for the Livermore Pool Type Reactor using a matrix of 840 cells, stored in two-dimensional form, is described. The code calculates the burnup of U/sup 235/on the basis of the megawatt days run during a fuel cycle and as a function of the neutron flux and fuel inventory in each of the 840 homogeneous cells in the reactor core. The thermal utilization and various other parameters for each core, and values for calculating the reactivity change between different cores can also be obtained. RHOBURN is written in Fortran for the IBM 7094, to be run under monitor control. The program listing and sample input and output are included. (auth)

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