regarding the xkcd, it's not really accurate (it seems to consider only the neutrons as "radiation"), for a somewhat better description see the first answer at

regarding the xkcd, it's not really accurate (it seems to consider only the neutrons as "radiation"), for a somewhat better description see the first answer at https://physics.stackexchange.com/questions/187605/does-water-absorb-neutrons https://physics.stackexchange.com/questions/187605/does-wate...