[en] An investigation of the importance of physical simplification in the ORIGEN code has been made by comparison with the BEGAFIP and CASMO codes. The most significant discrepancy seems to be due to the ORIGEN overestimation of the self-shielding effect on the neutron capture resonance integral of plutonium-240. This leads to an underestimation of the inventories of heavy nuclides with masses 241 through 246. In connection with the investigation, a recalculation of earlier presented inventories in spent fuel has been made, including studies of helium pressure build-up due to alfa decay, and neutron-induced activity in fuel rod construction materials. A rough estimation of plutonium recycle impact on radionuclide inventories in high-level waste has also been made. It is shown that recycling will have no dramatic effects on the inventories of radiologically significant nuclides. (author)