Effect of phosphate modification on incorporation of caesium nitrate by calcium aluminate cement

入澤 啓太; Mcgahan, M.*; 目黒 義弘; 木下 肇*

no journal, , 

Calcium aluminate cement modified with phosphate (CAP) has been studied as one of the alternative cementitious matrices for the encapsulation of nuclear wastes, especially those containing reactive metals. Our previous study indicated a potential advantage in phosphate modification of this system for incorporation of CsNO. Cs is one of the key radioactive nuclides which causes the majority of the radioactivity in the earlier age of nuclear wastes, yet difficult to incorporate into cement systems due to the mobile nature of an alkaline element. The present study investigates the compositional effects on the CAP system, focusing on the effects of phosphate on the incorporation of CsNO. The CAP samples were prepared by mixing calcium aluminate cement (CAC) with the aqueous solution of sodium polyphosphate and CsNO. In order to keep the weight % of CsNO constant in the prepared samples, the total weight of the matrix forming reagents (CAC and phosphate) were kept constant, as well as that of water. Only the balance between CAC and phosphate was changed to study the compositional effects. All samples were cured up to 28 days in a sealed container under ambient condition.