->  But anything/everything, in proper thickness, will
->  reduce/lower its level by half.  Ever pay attention
->  to x-ray technicians operating their equipment from
->  a "block house" while you're being exposed?

They are Behind a LEAD LINED wall and Looking Through High Lead
Content glass. Even then some just peak through the glass to see if you
changed your position and then duck behind the partition to take the
shot.



->  Concrete and iron/steel are the more popular materials.
->  Enough thickness and you reduce it by 1/2, 1/4/ 1/8,
->  1/16, etc etc etc.  Glass and plain ol' dirt work too.

High Level Gamma radiation is the Hardest to stop. They basicly require
a very high density substance like Lead or something higher o nthe
periodic table. Alpha and Beta can bascily be stopped by ones cloting or
anything with a higher density. 
Neutrons require water or plastics. The thickness depending on the
Neutron Density. For a Submarine Reactor from my Nuclear power days it
was about three feet of water and one foot of Poly Plastic as I recall
for the neutrons. And about 6 Inches of Lead for the Gamma Rays..
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