DURABILITY IN WATER OF MATRICES FOR RARE-EARTH – ACTINIDE FRACTION OF HIGH-LEVEL RADIOACTIVE WASTE

The durability in waters of matrices for rare-earth – actinide fraction HLW has been studied at 25 (1 atm.), 200 or 240°C (pressure of saturated vapor). The samples composed of Nd2ZrTiO7 (cubic pyrochlore-type structure) or Nd4(Ti,Zr)9O24 (orthorhombic symmetry, no natural analogue), phases were obtained by induction melting in a “cold” crucible. Leaching rate of Nd (imitator of REE-MA fraction) on the 28th day of experiment was lower than 5 × 10–8 g/(cm2 day). These results confirmed a very high durability of the ceramic waste forms in hot underground waters.