> A better solution is water. You need to carry it anyways.
You certainly won't be drinking that water after a while, though. Some might be used for cooling systems, but you would have a lot of extraneous water.
Why won't you drink it? Just because it's used for shielding doesn't make it radioactive.
Also water basically can't become radioactive. The isotope of oxygen with the longest half life, and more neutrons than the stable ones, has a half life of 26 seconds, so it doesn't stay radioactive.
If you manage to bind a proton (it's virtually impossible for oxygen, but lets say) and make fluorine, the result has a half life of less than an attosecond.
Deuterium is not radioactive, and tritium is hard to make (you need deuterium first, and there barely is any in your water).
The radiation could theoretically fission oxygen into other elements, but that's very unlikely, and the results have extremely short half lives.
In short: Water can't become radioactive, which is why it's so good as shielding. (However water can obviously be contaminated by something else that is radioactive - so don't go drinking the water in a nuclear reactor :)
You certainly won't be drinking that water after a while, though. Some might be used for cooling systems, but you would have a lot of extraneous water.