"For high atomic number materials, there is a chance of the beta particles loosing energy by producing some x-rays. In water, the x-ray production from a beta p

"For high atomic number materials, there is a chance of the beta particles loosing energy by producing some x-rays. In water, the x-ray production from a beta particle is quite miniscule." http://www.alpharubicon.com/basicnbc/RadiationPenetration.htm http://www.alpharubicon.com/basicnbc/RadiationPenetration.ht... By "high atomic number materials" they mean stuff like lead, 82. Aluminum is 13.