The ISS has a radiation "shelter" - the Destiny module. It is actually a laboratory but has extra shielding.
I suspect the design of spacecraft that go to Mars will involve using the water tanks as a radiation "bunker". Water is an excellent radiation damper. US nuclear submarines all have large water tanks forward of the reactor to protect the crew from reactor radiation. (The crew serving the engine spaces aft of the reactor, and the nuclear operators, all are permitted to absorb more radiation, and they get higher pay. No crew berthing is aft of the reactor, so those personnel are only exposed when they are on watch.)