I am all in on Thorium, though. I am puzzled as to why (except for the bad word “radioactivity”) it has not been pursued.
I guess that word is enough for a lot of people.
The biggest problem is decay products from U232 which is generated along with U233.
Ti208 and Pb207 are heavy gamma emitters and tend to build up.
This is the key reason U233 was never used for bombs.
The warhead would kill anyone doing maintenance on it.