Comparison of photon-production processing codes LAPHNGAS, MACK-IV, and NJOY

Several laboratories have independently developed computer codes that use evaluated data from the ENDF/B file to produce group-averaged cross sections and transfer matrices for neutron-induced photon production. There have been several instances in which these codes have produced discrepant data sets; such a situation naturally casts doubt on the validity of all the codes. For a series of specified test cases, the results from three of these codes (NJOY, LAPHNGAS, and MACK-IV) were systematically compared with each other and with hand calculations. Several shortcomings in the codes were discovered and repaired. One major difference of philosophy was resolved. Consequently, the codes have arrived at substantial agreement on all of the nearly 1200 nonzero group constants calculated in the study. Results are tabulated for future comparisons with other codes. 4 figures, 6 tables