DEVELOPMENT OF RUBBER-TYPE NEUTRON SHIELDS FOR TRANSPORT/STORAGE PACKAGINGS

Two kinds of rubber-type neutron shields for transport/storage packagings have been developed. In Type I, silicone rubber is the base material. Titanium hydride, boron carbide and other additives are included. This material offers good liquidity at processing, which makes it possible to apply this rubber shield to shapes with complicated geometry. The density is 1.8 gfcm3 . With Type II, ethylene-propylene rubber is the base material. Boron carbide, antimony oxide and other additives are included. This is a solid type shield, and machining is needed before fitting to the proper location. The density is 1.0 gfcm3. Several measurements were performed for both types to evaluate the shielding property, heat resistance, fire resistance, strength, weather resistance, thermal conductivity and thermal expansion. The neutron shielding ability of Type II is found to be better than that of water, while that of Type I is slightly less than that of Type II. A shielding calculation using a Monte Carlo code was performed to evaluate the measurement results. The experimental results and analytical results are in close agreement. The other main properties of the shields are as follows: The allowable temperatures of Types I and II are 170°C and 140°C, respectively; in the event of fire, both types are self-extinguishable in air.