Patent Number: 047524375
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging for radioactive materials. More particularly, it relates to a packaging in which a shielding material is buried and a method of manufacturing such packaging. 2. Description of the Prior Art A conventional packaging for radioactive materials has a resin layer on the surface of its shell made of forged steel in order to prevent neutrons from streaming out of the packaging. The packaging also has a plurality of fins projecting to the outside through the resin layer in order to dissipate heat from the radioactive materials therein. Since portions of the surface of the shell on which the fins pass through the resin layer lack the resin layer, some neutrons inevitably stream to the outside. Another conventional packaging is provided with hollows in its shell made of cast steel or forged steel and these hollows are filled with resins to shield neutrons. Such hollows are formed by extraordinary deep hole machining which is both troublesome and labor consuming. On the other hand, as a neutron shielding material, boron nitride or boron carbide has been used. As a neutron moderator accelerating the neutron absorbence of the shielding material, hydrogen-rich materials such as water, paraffin, wood, resin, or concrete have been known. However, when these materials are used as a shielding material for exothermic radioactive materials, they can only be positioned at a certain location because of the lack of heat-resistance and thermal conductivity. Materials having a boron exhibit a shielding effect against the thermal neutron characteristic zone alone. Materials containing hydrogen as a neutron moderator are required for a dry-type transportation packaging or a dry-type storage packaging for nuclear fuels containing fast neutron, and thus, has to be excellent in terms of both heat-resistance and thermal conductivity characteristics. Materials such as synthetic resins are generally used. Since the resins lack both heat-resistance and thermal conductivity, they should be used together with aluminum and/or carbon to supplement these defects. SUMMARY OF THE INVENTION The packaging for radioactive materials of this invention which overcomes the above-discussed disadvantages of the prior arts, comprises a packaging body made of cast iron or cast steel, and a shielding material which is cast within said packaging body in the casting of said packaging body. The shielding material is at least one selected from the group consisting of heavy metals, concrete, organic materials, ceramics, boron nitride, boron carbide, graphite and hydrogenous alloys. The shielding material may be interjected inside the case which is cast in said packaging body in the casting of the packaging body. The case is made of heat-resistant materials such as steel pipes, steel plates or ceramics. The shielding material is continuously disposed in the circumferential direction within said packaging body. As the method for manufacturing the packaging for radioactive materials, a shielding material is positioned in a mold for the packaging body, and cast iron or cast steel is poured in the mold thereby forming the packaging in which said shielding material is cast. The shielding material may be charged inside a case made of heat-resistant materials and then said case is positioned in the mold. Thus, the invention described herein makes possible the objects of (1) providing a packaging which can attain an effective shielding of .gamma.-rays and neutrons from streaming therefrom; (2) providing a packaging wherein a shielding material is easily and firmly installed; (3) providing a packaging which can be manufactured with ease; and (4) providing the method for manufacturing the packaging.