[CamperBob2]

Sounds like they get blasted pretty hard, with the equivalent of several hundred chest X-rays over a 6-month tour.

[rdl]

A shuttle mission is at most 3-4 mSv/day, and depends on orbit. ISS is about 80 per 180 day mission. A whole-body CT is 10-12 mSv. Non-trivial, but not huge.