[en] The fission product gamma spectra of ²³³U, ²³⁵U, and ²³⁹Pu were measured at 12 cooling times following 20,000-s irradiations in the thermal column of the Omega West Reactor. The mean cooling times ranged from 29 s to 146,500 s. The total gamma energies were obtained by integrating over the energy spectra, and both the spectra and the total energies are compared with calculations using the CINDER-10 code and ENDF/B-IV data base. The measured and calculated gamma spectra are compared in a series of figures. The measured total gamma energies are approx. 14% larger than the calculated energies during the earliest counting period (4 s to 54 s cooling time). For ²³⁵U, the measured and calculated total gamma energies are nearly the same after 1200 s cooling time, and the measurements are 2% to 6% lower at longer cooling times. For ²³⁹Pu, the measured and calculated total gamma energies are nearly the same at cooling times longer than 4,000 s, and for ²³³U this condition prevails at cooling times longer than 10,000 s. 39 figures, 4 tables