Energy content of nuclear waste

E=MC².

High level wastes have considerable energy which dissipates fairly quickly.

I see no reason why this coudn't be put into an insulated container, and the heat liberated used to raise steam and hence generate power.

The waste could then be reprocessed to extract the valuable stable products of decomposition and the remaining radioactive material combined with fresh high level waste to continue the process.

Medium level waste is a bigger problem which could be treated in a similar way, but due to the longer half lives involved, the specific output would be lower and the plant would have to be run for longer after the primary nuclear reactor has been decommissioned.