I need information/references/help in determining the shielding required for the following: Ra-Be source: 3 Ci in a 20.7 mm dia.x 35.5 mm long capsule. Dose outside the shielding to be limited to 100 mr/hr. Options: Shield materials: concrete (borated), steel, polyethylene (borated). Containers: 55 gal. drum (22" dia x 33" high)or B-25 box (4'W x 4'H x 6'L) Thanking you for your support,