Patent Number: 
Section: claims

1. A neutron shielding material containing epoxy resin as one of main component, comprising a hardened material which is prepared by mixing a base resin which contains a compound including two or more epoxy groups in the molecule as at least one component with a hardener for opening said epoxy rings and polymerizing thereof by heat setting said base resin at a temperature higher than room temperature. 2. A neutron shielding material containing epoxy resin as one of main component, comprising a hardened material which is prepared by mixing a base resin which contains a compound including two or more epoxy groups in the molecule as at least one component with a hardener for opening said epoxy rings and polymerizing thereof, wherein the setting temperature is approximately 40xc2x0 C. or higher. 3. A neutron shielding material according to  claim 1  or  2 , wherein said base resin is a member selected from the group of bisphenol A epoxy compound, novolak epoxy compound, alicyclic glycidyl ether type epoxy compound, various glycidyl ester type epoxy compound, glycidyl amine type epoxy compound, and biphenol type epoxy compound or a mixture thereof, and said hardener is a member selected from the group of amine type hardener such as aromatic amine, alicyclic amine, and polyamide amine, acid anhydrate type hardener, and imidazole type hardening promoter or a mixture thereof. claim 1 2 4. A neutron shielding material according to  claim 3 , wherein hardened material contains a fire retardant that said base resin contains. claim 3 5. A neutron shielding material according to  claim 4 , wherein said fire retardant contains a member selected from the group consisting of metal hydroxide such as magnesium hydroxide, aluminum hydroxide, and calcium hydroxide, hydrates of said metal oxide, inorganic phosphoric compounds such as ammonium phosphate, organic phosphoric compounds such as phosphoric ester, and halogenated compounds such as hexabromo benzene and tetrabromobisphenol A. claim 4 6. A neutron shielding material according to  claim 5 , wherein said hardened material contains a neutron absorbing material that is added to said base resin. claim 5 7. A neutron shielding material according to  claim 6 , wherein said neutron absorbing material contains a member selected from the group consisting of boric compounds, cadmium compounds, gadolinium compounds, and samarium compounds. claim 6 8. A neutron shielding material according to  claim 7 , wherein said hardened material contains a metal hydride or a hydrogen-absorbing alloy that is added to said base resin. claim 7 9. A neutron shielding material according to  claim 3 , wherein said base resin and said hardener are so mixed that the equivalent ratio of the active hydrogen group in said amine type hardener to the epoxy group in said base resin may be 0.7 to 1.3 when the amine type hardener is used as said hardener or the equivalent ratio of the total of active hydrogen group and acid anhydride to the epoxy group in said base resin may be 0.7 to 1.3 when the amine type hardener is mixed up with the acid anhydride. claim 3 10. A neutron shielding material according to  claim 5 , wherein said fire retardant, if it is a metal hydroxide or hydrate of said metal oxide, is added to said base resin at a ratio of 30% to 60% by weight of said base resin. claim 5 11. A neutron shielding material according to  claim 7 , wherein said neutron absorbing material, if it is a boron carbide or boron nitride, is added to said base resin at a ratio of 0.1 to 10% by weight of said base resin. claim 7 12. A neutron shielding material according to  claim 8 , wherein the components of the neutron shielding material are mixed up so that the viscosity of the liquid mixture of said base resin and said additives may not exceed 200 dPa.s immediately after addition thereof at 30xc2x0 C. to 100xc2x0 C. claim 8 13. A neutron shielding material according to  claim 8 , wherein the components of the neutron shielding material are mixed up so that the viscosity of the liquid mixture of said base resin and said additives may not exceed 200 dPa.s at 30xc2x0 C. to 100xc2x0 C. for at least one hour. claim 8 14. A neutron shielding material according to  claim 8 , wherein the components of the neutron shielding material are mixed up so that so that the hydrogen number density of the compound of said base resin and said additives may be 5xc3x9710 5  hydrogen atoms/cm 3 . claim 8 15. A neutron shielding material according to  claim 5 , wherein said fire retardant is mixed so that the oxygen index of said hardened material after heating may exceed 20. claim 5 16. A neutron shielding material according to  claim 5 , wherein the mean grain size of magnesium hydroxide is 0.5 to 5 xcexcm when magnesium hydroxide is used as said fire retardant. claim 5 17. A neutron shielding material according to  claim 8 , comprising said hardened material which is obtained by reading said base resin with said additives at 30xc2x0 C. to 130xc2x0 C. as the first-order hardening and then reacting thereof at 130xc2x0 C. to 180xc2x0 C. as the second-order hardening. claim 8 18. A neutron shielding material according to  claim 8 , comprising said hardened material which is obtained by reacting said base resin with said additives at room temperature as the first-order hardening and then reacting thereof at 60xc2x0 C. to 180xc2x0 C. as the second-order hardening. claim 8 19. A spent-fuel storage cask comprising an outer shell, an inner shell provided inside said outer shell, a basket provided inside said outer shell to store spent fuel assembly, and a neutron shielding material according to  claim 1  which is placed between said inner and outer shells. claim 1 20. A spent-fuel storage cask comprising an outer shell, an inner shell provided inside said outer shell, a basket provided inside said outer shell to store spent fuel assembly, and a neutron shielding material according to  claim 2  which is placed between said inner and outer shells. claim 2