The space is not really a fun-only place to be. The astronauts are exposed to the insane amount of radiation, and iodine tablets are indispensable.
Low Earth orbit is not bad, and astronauts have stayed a year or longer. It's the missions into interplanetary space that will involve excessive ionizing radiation, to the point of potentially being debilitating over the course of the mission. There's also a non-trivial risk from coronal mass ejections (from the sun) which *do* involve an insane amount of radiation ("insane" as in fatal) if you happen to be unlucky enough to be in their way.
Iodine tablets only make sense when one is exposed to nuclear fission byproducts (from nuclear reactors, nuclear waste, or nuclear bombs) which may include a radioactive isotope of iodine, I-131. Taking the iodine pills in advance of exposure saturates the thyroid gland with non-radioactive iodine, so when I-131 is ingested the thyroid tends to not take it up quite as much. Otherwise iodine tablets are of no use for radiation exposure. Link:
http://emergency.cdc.gov/radiation/ki.asp