Gibbsite- and kuzelite-based matrix for the preservation of radioactive aqueous sodium nitrate concentrates

Abstract

The article studies the possibility of using a matrix of gibbsite and kuzelite for the preservation of liquid radioactive wastes consisting of aqueous NaNO₃ concentrates. The matrix is formed during the solidification of these wastes with cement, consisting of calcium aluminate and gypsum. The requirements for cemented solid waste are met by a matrix obtained from a mixture of the following composition: 45.2%-NaNO₃ solution 53.04%; gypsum—5.4%; calcium aluminate—36.16%; diatomite powder treated with polydiallyldimethylammonium chloride (polyDADMAC)—5.4%. The matrix has the following characteristics: ratio of matrix and cemented solution volumes—1.45; average ¹³⁷Cs leaching rate for 90 days—1.4∙10⁻⁴ g/(cm²∙day); strength—15.2 MPa, including after the tests for water resistance, 30 freezing-thawing cycles, and irradiation to a dose of 1 MGy—6.8, 15.4, and 9.6 MPa, respectively.