Patent Number: 
Section: claims

1. A method for decontaminating radiocontaminated grains, the method comprising: a pretreatment step of mixing radiocontaminated grains and a sodium phosphate-based dispersant; and a decontamination step of mixing the radiocontaminated grains processed by the pre-treatment step and paper sludge-derived sintered carbonized porous grains so as to incorporate radioactive 134Cs and 137Cs of the radiocontaminated grains in the sintered carbonized porous grains. 2. The method for decontaminating radiocontaminated grains according to claim 1, wherein the sodium phosphate-based dispersant contains at least one compound selected from the group consisting of sodium hexametaphosphate, sodium tripolyphosphate, and sodium tetrapyrophosphate. 3. The method for decontaminating radiocontaminated grains according to claim 1, wherein at least one ion-exchangeable compound selected from the group consisting of potassium chloride, magnesium sulfate, and copper sulfate is impregnated in the sintered carbonized porous grains, these sintered carbonized porous grains and the radiocontaminated grains processed by the pre-treatment step are mixed together, and the radioactive 134Cs and 137Cs of the radiocontaminated grains are incorporated in the sintered carbonized porous grains by ion-exchange. 4. The method for decontaminating radiocontaminated grains according to claim 2, wherein at least one ion-exchangeable compound selected from the group consisting of potassium chloride, magnesium sulfate, and copper sulfate is impregnated in the sintered carbonized porous grains, these sintered carbonized porous grains and the radiocontaminated grains processed by the pre-treatment step are mixed together, and the radioactive 134Cs and 137Cs of the radiocontaminated grains are incorporated in the sintered carbonized porous grains by ion-exchange. 5. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium hexametaphosphate. 6. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium tripolyphosphate. 7. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium tetrapyrophosphate. 8. The method for decontaminating radiocontaminated grains according to claim 3, wherein potassium chloride is impregnated in the sintered carbonized porous grains. 9. The method for decontaminating radiocontaminated grains according to claim 3, wherein magnesium sulfate is impregnated in the sintered carbonized porous grains. 10. The method for decontaminating radiocontaminated grains according to claim 3, wherein copper sulfate is impregnated in the sintered carbonized porous grains. 11. The method for decontaminating radiocontaminated grains according to claim 4, wherein potassium chloride is impregnated in the sintered carbonized porous grains. 12. The method for decontaminating radiocontaminated grains according to claim 4, wherein magnesium sulfate is impregnated in the sintered carbonized porous grains. 13. The method for decontaminating radiocontaminated grains according to claim 4, wherein copper sulfate is impregnated in the sintered carbonized porous grains.