The neutron spectrum and criticality of ZPR-3 Assembly 11 have been calculated using estimated cross sections for the mU(n, γn’) reaction. Inclusion of this reaction markedly improves agreement between the measured and calculated spectra, and it also decreases the calculated criticality by 0.62%. This change in criticality can be compensated for by lowering the 238U capture cross section from the ENDF/B-III values to those of a recent microscopic measurement. These and other ramifications of the (n,γn’) reaction in fast reactor assemblies are discussed.