@Jolanta Agent orange was a combination of 2 widely used herbicides 2,4,5 T, and 2,4 D that had been in agricultural use since the 1940s, just never in the concentrations apply in SEA. Prior to the use of AO, the defolient of choice was incindigel, jellied jet fuel with a white phophourous fuse. (NAPALM replacement).
In the case of spent U, in response to increasing hardening of targets, the need for harder and harder bullets for penetration was a major interest. The advantage of U over Fe(iron) was that U is harder than Fe and heavier than Pb (lead). The intial product of spent U was not seen as a hazard over 10 years, as it is not. However omitted from the data presented in acceptance of spent U projectiles was the decay daughters and their likelihood of enviromental presence over the longer term.
Both of these are very similar to the use of mines, gravity bombs, and clusterbombs in wartime, very little thought is given to the future removal or the morality of their initial use.
Unfortunately current cost/benefit analysis is the primay decision critiria.