A variational procedure for calculating fast-energy few group constants is described. For a given medium, the method permits one to express the flux and current solutions of the Boltanann equation treated according to P-l slowing-down theory in each group of a few-group scheme as a linear combination of two base flux spectra, to obtain the group flux, and as a linear combination of two base current spectra, to obtain the group current. The coefficients for combining the base spectra are provided by the theory and depend only on the concentrations of the component elements of the medium. Once the flux and current spectra in each group are calculated, the group constants for the medium can be easily calculated from base-flux-spectra weighted library microscopic cross sections. Group constants calculated in this manner agree well with those obtained from the MUFT 5 program.
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