Radiation in Lunar Regolith

>
>>Does anyone have data on how much radiation we can expect from the
>>lunar regolith that we might be using to shield future settlements
>>from cosmic rays?
>>
>I don't have data on this, but my expectation would be that lunar regolith in
>average is less radioactive than Earthling soil. The Moon is a lighter orb
>and therefore the proportion of heavy elements should also be lower - and
>radioactive elements are *very* heavy -
>

Also note that radon is a gas, and a heavy one, which is why it's a
ground-level problem for homes etc. But if the regolith in question was
on the OUTSIDE of a spinning habitat, (1) it would blow away into space,
since "down" is actually "out" and a vacuum, and (2) given that the
habitat has to be air-tight anyway, very little of it should get in
through the seals. You might want to make sure the very outer layer of
the habitat is porous to radon to be sure it would get out. But I think
it would be safe to assume radon will not be a significant source of
radiation in most space habitats.

Arthur