This one is 100% true.

Depleted uranium is what is left over after most of the U-235 is removed from naturally occurring uranium. It is mostly U-238, which is non-fissionable (it can’t support a chain reaction). There are other metals that are more dense than depleted uranium, but they are more expensive, so they use depleted uranium and add a small amount of other metals to make it a hardened alloy.

Uranium-238 has a very long half-life of billions of years, so it decays very slowly and produces very little radiation. All of the radiation from U-238 is alpha radiation, which does not penetrate very well – it can be stopped by a sheet a paper and only travels a few inches in air. Some of the daughter isotopes in the uranium decay series produce beta and gamma radiation but the majority of radiation in the complete decay of uranium to a stable isotope is in the form of alpha radiation. Only the surface of the rounds will actually emit alpha radiation into the air, and that radiation will only travel a few inches.

So nearly all of the radiation from depleted uranium will be converted to heat before it reaches any of the soldiers inside a vehicle that is carrying depleted uranium ammo. This heat will contribute a small portion of the heat within the vehicle but, for example, in a tank most of the heat will come from the putt-putt engine used to power the vehicle. In fact the body heat from the soldiers produces more heat energy than the radiation from the decay of the uranium in the ammo rounds.

There is a potential danger though from the depleted uranium rounds (beyond their use as a deadly weapon). If microscopic pieces of the depleted uranium are dislodged from the material and become airborne, like when the shells are bumped together or scraped, then those airborne particles can be breathed in and become lodged in the lungs or ingested into the digestive system. In that case then the alpha particles can strike tissue and damage DNA which could cause cancer. If a sliver of the metal penetrates the skin, that can also potentially cause damage to the DNA of the tissue it is in contact with.

Also, one of the daughter elements in the decay of uranium is radon, which is a gas. So when the radon is produced it can be released into the air inside the vehicle. Since radon has a half-life of about four days, it can decay into polonium particles in the air (which have a half-life of about a month) and the radon and polonium can accumulate in the vehicle and get into the lungs where it can damage tissue. If the vehicle is well ventilated then there is little risk of that happening.

OK, there’s more but this way too long already...

#Patsplaining