First off the ways we have with dealing with the waste have radically improved over the last 50 years.

Do you really think that no one will develop new types of power station that use different types of fissile material?

Clathrates are great... except they are so delicate considering they are methane in a ice matrix which at room temperatures and pressures would explosively decompose. Into this we should be drilling large holes, pumping in CO2 and this is safer than storing some waste in caverns?