Oli Wilson answered on 17 Nov 2017:
It would partly depend on what sort of radiation it was shooting out. There are three basic types: the bus, the bullet, and the death ray.
– The bus: alpha particles are kind of slow but unbelievably heavy (for radiation). That means they get stopped quite easily but do huge amounts of damage as they do. You can stop alpha radiation with a piece of paper, so the lining of your guts would get blasted but nothing further. If those intestinal cells hung around for long enough you’d run the risk of getting cancer.
– The bullet: beta particles are much faster and lighter than alpha. You need aluminium to stop them, but that means that they generally cause slightly less damage to the stuff they pass through. You could probably notice these from outside if you swallowed a beta-emitter, and you’d still have a high risk of getting very sick.
– The death ray: gamma rays don’t weigh anything at all – they’re basically the same as radio waves, infrared and light, just with more energy. This means they’re really tough to stop, but that they just kind of ignore your cells, mostly (which is good).
Unfortunately, most radioactive things will emit all these things, so aim not to swallow any! Unless a doctor tells you to, of course – they can be used to make scans more effective, and to help in cancer treatments.
Yo Yehudi answered on 17 Nov 2017:
Have you ever read about the “Radioactive Boy Scout”, David Hahn? https://en.wikipedia.org/wiki/David_Hahn
In the 90s, this poor kid was obsessed with making a nuclear reactor, and went about it with alarming dedication. He was discovered making the reactor in his back yard in the shed! He’d been collecting components from dismantled smoke detectors, clocks, and other household items that have small amounts of radioactive material. Eventually the police found out about it and shut everything down, but that wasn’t even the end of it – he was convicted some years later for trying to steal radioactive material again! At the time it looked like he had sores all over his face, probably from radiation sickness, and he ended up dying quite young (39) – while it’s confirmed as alcohol poisoning it’s hard not to suspect that his body was probably doing badly from handling so much radioactive material without proper safety precautions!