Study of the Stability of Aluminophosphate Glasses–Matrices for Immobilization of Radioactive Waste

Abstract

Liquid radioactive wastes of the reprocessing of spent nuclear fuel are included in a glassy Na–Al–P matrix for subsequent placement in underground storage. More than 6200 tons of such wastes have already accumulated on PO Mayak (Chelyabinsk region), and the total amount of waste by 2020 is estimated at 12000 tons. The stability of the glass matrix in underground water depends on the change in its phase composition due to heating during the decay of radionuclides. This process is accelerated by the catalytic effect of water vapor. Before the encapsulation, a small amount of water enters into the package with the waste as wet air. After the corrosion of the package in a repository, the destruction of the glass matrix in contact with the heated vapor will be accelerated: the hydration of the glass followed by its crystallization occurs. This phenomenon has a negative effect on the ability of the matrix to hold radionuclides under its subsequent contact with water, which should be taken into account in the long-term performance assessment of the underground repository.