Patent ID: 8207391

Claim:
A method of fixing radioelement by obtaining crack resistant solidified article suitable for final disposal, in which an absorbent that has absorbed radioactive iodine or radioactive anion species in a waste water is dispersed in a matrix of the solidified article, comprising: preparing, by a spray drying, spherical particles of layered double hydroxide, wherein an average particle diameter is in the range of 1 to 200 μm, wherein the layered double hydroxide is a nonstoichiometric compound represented by general formula (a) or (b): [M 2+ 1-x M 3+ x (OH) 2 ] x+ [A n− x/n ·mH 2 O] x− . . . (a), [Al 2 Li(OH) 6 ] x+ [A n− x/n ·mH 2 O] x− . . . (b), wherein 0.1 ≦x≦0.4; 0 <m; n represents a natural number of 1 to 4; M 2+ represents at least one divalent metal selected from Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn; M 3+ represents at least one trivalent metal selected from Al, Fe, Cr, Ga, and In; and A n− represents at least one n-valent ion-exchangeable anion selected from OH − , Cl − , Br − , CO 3 2− , NO 3 2− , SO 4 2− , Fe(CN) 6 4− , or tartrate ion; adsorbing the iodine or radioactive anion species to the particles of layered double hydroxide; mixing the particles of layered double hydroxide (A) that has adsorbed the iodine or radioactive anion species with a powdery fixing agent (B) comprising at least one of hydroxyapatite and fluorapatite, wherein the mixing ratio of the hydroxide particles (A) to the fixing agent (B) is in the range of (A):(B) =5:95 to 60:40 in terms of the mass ratio, thereby obtaining a mixture; filling the mixture in a mold; forming a compact of the mixture under pressure of 5 to 100 MPa; and sintering the compact at a temperature of 700 to 1200° C. while or after the compact is formed.