Neutron absorbers

Purpose: To obtain a plate-like neutron absorber of about 3 - 5 mm thickness easy to fabricate which produces no gamma rays and exhibits desired neutron absorbing effect, by blending a polyethylene resin with a specific amount of an inorganic lithium compound. Constitution: 250 - 450 parts by weight of an inorganic lithium compound are blended to 100 parts by weight of a polyethylene resin. Preferred polyethylene resin used herein is a high density polyethylene resin having a density of more than 0.950 g/cm3 and a molecular weight of more than 30,000 and preferred inorganic lighium compound used herein is, for example, lithium fluoride having 0.5 - 500 μ of weight average grain size. Upon preparing the above composition, a part of the inorganic lithium compound is previously dry-blended with the polyethylene and then melted and kneaded uniformly and, thereafter, the remaining part of the inorganic lithium compound is successively added uniformly under melting and kneading. (Moriyama, K.)