Systematic investigation of the strontium zirconium phosphate ceramic form for nuclear waste immobilization

摘要

We have summarized our data and literature ones on the thermophysical properties and hydrolytic stability of Sr0.5Zr2(PO4)(3) compound as a host NaZr2(PO4)(3)-type (NZP) structure for immobilization of Sr-90-containing radioactive waste. Absence of any polymorphic transformations on the temperature dependence of its heat capacity between 7 and 665 K is caused by the stability of crystalline Sr0.5Zr2(PO4)(3). Calculated values of thermal conductivity coefficients at zero porosity in the range 298 -673 K were 1.86-2.40W.m(-1).K-1. The compound may be classified as low thermal expanding material due to its average linear thermal expansion coefficient. Study of the hydrolytic stability in acid and alkaline media has shown that the relative mass fraction of Sr2+ ions, released into aggressive leaching media, didn't exceed 1% of the mass of sample. Soxhlet leaching studies have shown substantial resistance towards the release of Sr2+ ions into distilled water. Feeble sinterability constrains practical applications of NZP substances, that is why known in literature methods of Sr0.5Zr2(PO4)(3) dense ceramics obtaining have been reviewed. (C) 2016 Elsevier B.V. All rights reserved.