Radation shielding pellets

#This invention relates in general to radiation shielding means, and more particularly to radiation shielding pellets containing at least two shielding materials within individual pellets.

#Radiation shields often contain more than one type of material in order to provide attentuation over the entire spectrum of incident radiation. One common type of shielding application requires a gamma ray shielding metal such as tungsten or steel in combination with a hydrogen-rich neutron shielding material such as lithium hydride.

#Since the radiation shield must provide uniform attenuation over a large surface area, the two required materials must be prevented from separating within the shield. This means that lithium hydride in a shield must be trapped in place. If it is allowed to liquify or form vapor bubbles, portions of the shield volume will come to have an incorrect ratio of LiH versus metal, and shielding will not be uniform.

#FIG. 1 is a diagram of a shield containing pelletized shielding material.

#FIG. 2 is a diagram of an individual pellet.

#FIG. 3 is a diagram illustrating one method of manufacture 8 for pellets of shielding material.

#FIG. 1 is a diagram of a shield containing pelletized shielding material. Shield retaining wall 10 may be of any convenient shape or material consistent with structural requirements. Pellets of shielding material 20 are used as fill within the shield. Pellets 20 may be of any convenient size. However, pellets of about one-quarter inch length are conveniently handled and placed into shields of odd shapes.

#FIG. 2 is a diagram of an individual pellet. The outer shell of the pellet 21 is composed of a high melting point material, for example tungsten, molybdenumn, depleted uranium, or iron. This material will inhibit the passage of particular types of radiation and not inhibit to the same extent other types of radiation.

#Filling 22 comprises another type of shielding material. Ideally, this material will have shielding properties complementary to those of the outer shell. Thus, the radiation which the material in the outer shell does not shield against tends to be absorbed by materials inside the pellets. Lithium hydride is a typical material that can be used for filling of pellets. Typically, the filling material may be any substance which is rich in hydrogen. Thus, paraffins, plastics, and other hydrocarbon-rich materials could be used. If a thick outer shell is employed, water would also be a suitable filling material. Typically, the outer shell material will be a heavy metal with a higher melting point than the filling. Typically, a hydrogen-rich pellet filling will retard neutrons, and a heavy metal shell will act against gamma rays.