Quite a vague question but an attempt
Alpha emitters: 1 sheet of paper is sufficient.Now most alpha emitters also have a gamma component.
Beta RadiatorS: 2 á 3 cm plastic.Here light materials are chosen to avoid the Bremstrahlung as much as possible. But in itself that is not a really big problem. A few cm of concrete or brick will stop the betas and the Bremstrahlung.
Gamma: With 1 metre of concrete it is already quite far but if I want to build up extra safety you can bring it to 1.5 or 2 m and then everything is stopped.
A nuclear reactor usually has what one calls a biological shield.Actually, that is the concrete structure where the reactor barrel sits in/hangs. A bit dependent on the reactor type are these 1.5 and 3 m thick. But in part, that is also to provide the necessary mechanical strength (seismic protection in process). When the reactor is running, one can then stand on the outside of this biological shield. Only the spaces under the reactor are still filled with some of the technical installations that are needed and usually also give off radiation. But I have been in several reactors during the operation until close to this biological shield.
As the last great source we have the neutrons.Around a reactor there are also a lot of neutrons. Especially if one would succeed in building fusion reactors in the future that will be a problem.
Here one uses best layered shielding.First a low density to thermalize the neutrons (if that is not yet done in the reactor) and then a special layer that captures a lot of neutrons such as cadmium or boron. And then some lead or concrete to stop the gammas of the neutron capture.
Perhaps a final remark related to stopping gamma radiation.The absorption of gamma radiation follows an exponential gradient in the guards. The first CMS therefore reduce the radiation very strongly and in the beginning the amount of radiation that comes back is very fast. But to stop the last radiation, a lot of material is needed. Now at and at the moment the radiation that is naturally present in the building materials will become larger than the radiation that comes from the source and is extra thickness so not useful anymore.
First: What we mean by radiation.Radiation is the emitting of energy as waves (electromagnetic radiation) or as particles (particle radiation, like alpha radiation and beta radiation); Incidentally, according to contemporary quantum mechanical opinions, there is no fundamental difference in this.
Well, that’s me quite a bit.
Then you are talking about densities.Also there you have quite a bit of difference. The density or specific mass of a homogeneous material in physics and chemistry is an intensive quantity that expresses the mass of the material present in a given volume…. Often the obsolete and erroneous term specific gravity is used.
Let’s keep it with densities that are known to us, so that a block of a cubic decimeter weighs about 7 kg.Materials can be incredibly much closer. Think of the density of a white dwarf (our sun over 5 billion years), there weighs a cubic decimeter a few tons. With a neutron star that is still a bit more extreme, a cubic decimeter has the mass of the Mnt Everest, or better two mount Everesten… You can imagine that this type of material is very low in radiation. I think only the WIMPS save it. About WIMPS further.
Well, that was that.Matter on our well-known scale. Now the question itself: how thick should walls be to stop radiation. And the variation here is even bigger if possible. With a thin skin paper, you stop light photons. Try it. Electrons are also easy to stop. High-energy radiation penetrates substances better, just think of radioradiation. Wall of 50 cm thick works fine here.
And then we come to the troublesome brethren, who have nothing and none of them.First of all the neutrinos. We can have neutrinos, particles that move with the speed of light but which seem to possess mass,… Here I stop, because it simply cannot. Each particle, however little mass it possesses, can never go with the speed of light. And yet measurements indicate that the flash of a supernova at light years distance shows a neutrino emission at the same time. Indeed, with the speed of light. The neutrino is therefore a very weird particle. We certainly do not know the fine of it yet.
Then we come upon even more weirder particles, the wimps.Weakly Interacting Massive Particles.
Particles that do have mass but do not attract anything from ordinary matter.There you have not enough on a lead wall of a light year thick, they just cycle through it.
In General, you can say that particles like all other, ordinary matter, are quite easy to stop off.Radiation is a bit trickier but with a lead wall of a metre thick you put yourself well out of the wind in this respect. Neutrinos are already asking for a thicker lead wall. A wall of 100,000 km holds 50% of these particles (estimation on my part, the order of magnitude is correct). The WIMPS do not attract anything. Nowhere? Well.. Only of gravity.
To completely mute neutrino radiation, walls of a few light years are needed thick.