IMPROVEMENT OF A HIGH-LEVEL-WASTE IMMOBILIZATION BARRIER - CRYSTALLINE PHOSPHATE MATRICES

Crystalline complex phosphates of the NZP structure are studied as ori ginal matrices for incorporation of radionuclides that ensure effectiv e retention of various nuclear wastes components. Single-phase phospha tes containing Cs, Sr, REE, and tetra- and pentavalent d-transition el ements are prepared. The crystal-chemical principle of the isostructur al replacements that form the complex phosphates is discussed. The lea ching characteristics of Cs and Sr are found. Possible ways of improvi ng the chemical stability of the crystalline phosphates are discussed. A two-tiered immobilization barrier is created firstly by the particu lars of the crystal structure and secondly by the degree of structural imperfection.