The Boondocks by Aaron McGruder for February 28, 2019

That depends on what kind of radioactive material. The majority of radioactive isotopes are alpha or beta emitters, often with a long half-life. Plutonium 239, for instance, has a half-life of 24,000 years and is an alpha emitter. Having a long half-life means that it’s not very active. Alpha particles are stopped by a sheet of cardboard or a foot of air or a few inches of water. Plutonium 241 is a beta emitter with a 14 year half-life. Beta particles require plywood or a few more feet of air or water to stop. Plutonium 239 is not particularly dangerous… unless you eat some, as it’s a heavy metal, and you will die of heavy metal poisoning. And, oh yeah, if you stick too much Pu-239 in one place you get a different nuclear reaction: spontaneous fission. It is advisable to be a few kilometers away when that happens. It is probably a good idea to stay, say, five feet away from Pu-241. Pu-244 is also an alpha emitter, and has a 80 million year half-life; it’s effectively inert, again as long as you don’t pile a lot of it in one place. Some radioactive isotopes emit neutrons and/or gammas; those require lots of lead, concrete, or water to stop. Cobalt 60 is a beta/neutron/gamma emitter with a half-life of 5 years. Stay far away or you will die. Co-60 is used in medical radiation systems, to zap cancers on the principle that it kills the cancer faster than it kills you. Sometimes it works. Note that the pretty blue or green glow emitted by some radioactive substances is Cherenkov radiation: that item is kicking out particles which move faster than light in air or water (slower than light in a vacuum, of course) and it would probably be a good idea to be elsewhere, even if it is only alphas or betas.

A will won’t mean much if there’s no one around to inherit the things that aren’t around either!

From the instructions for entering the fallout shelter they gave us in my youth:

“If there’s any fallout on you, brush it off”.