4. METHOD OF SOLUTION
The 68 fine-group fluxes and currents are calculated by one sweep through the group structure, starting from a specified source distribution. The source may be selected from among the eight available on the data tape or may be input. The multigroup model uses a full downscattering matrix, with inelastic, (n,2n), and P0 and P1 components of elastic scattering explicitly included. Macroscopic fine-group parameters are constructed from input nuclide concentrations and microscopic parameters, available on the data tape for more than 200 individual nuclides. There is no restriction, other than availability, on the number of nuclides usable in a case. A special calculation is made in the resonance range for certain nuclides, using an adaptation of the Adler, Hinman, and Nordheim method to obtain an intermediate resonance approximation for both the absorber nuclide and an admixed moderator. The resonance contribution is allocated to the fine-groups in a consistent manner providing self-shielding in both space and energy. Additional self- shielding factors may be read in for any nuclide, if desired. The fine-group fluxes and currents are used as weighting functions in averaging macroscopic and microscopic parameters over the specific option, the neutron age in an infinite medium may be calculated by the moments method.