Looking ahead to final disposal of high-level radioactive waste arising from further utilization of nuclear energy, the effects of burn-up of LWR with UO2 and MOX fuel and extended cooling period of spent fuel on waste management was discussed. It was assumed that the waste loading of vitrified waste is restricted by three factors: heat generation rate, MoO3 content, and platinum group metal content. As a result of evaluation for effects of extended cooling period, the waste loading of vitrified waste generated from both UO2 and MOX fuel could be increased in the current vitrification technology. For the storage of the MOX fuel vitrified waste with higher waste loading, however, those vitrified waste require long storage period because decay heat of 241Am contributes significantly. Therefore, the evaluation of effects of Am separation on the storage period was performed. The results showed, 70 to 90% of Am separation is desirable to shorten the storage period. These results indicate that nuclides separation could be one of efficient solutions in order to cope with extension of cooling period of spent fuel.