As buried in [arstechnica]:

In a recent article reporters covered the development of a new cargo module, SpaceX's Dragon XL, which would service the proposed Lunar Gateway. Buried within the comments though was a helpful little link to a NASA Space Radiation ebook that covers the ins and outs of solar radiation, space weather, and exposure limits for astronauts over their carrier, among other things.

You can grab the book [here] as a pdf.