Should every country, that operated nuclear facilities care for its own nuclear waste?
This policy will deter countries from utilizing nuclear facilities.
If you operate a nuclear power plant, you get the revenue and therefore, you are responsible for the waste, you produced.
More diversity in nuclear waste disposal solutions is unsafe for the humanity.
The electric power, produced by the nuclear power plants was fed into a power grid, that is normally not only national limited. Therefore, the power was also used by different countries. So all the countries, that used nuclear power have to care for the waste together.