Thorium

The fission of Thorium does not produce unmanageable nuclear waste like Uranium. In its fission by-products there are very little traces of transuranides. As little that all those long live products can be transmuted... in Thorium reactors.

Of particular concern in nuclear waste management are two long-lived fission products. The most troublesome transuranic elements in spent fuel are Np-237 (half-life two million years) and Pu-239 (half-life 24,000 years).

Those products are produced by the capture of neutrons by the U-235 or U-238 without starting the fission reaction.

As Thorium atomic mass is smaller than Uranium (232 versus 235 and 238), the production of those transuranic elements by excedentary neutrons is theoretically lower.

This is confirmed by experimentation.