Wet chemical processing for nuclear waste glass to retrieve radionuclides

摘要

Here, we show unexpected and significant elution behavior of various elements from simulated nuclear waste glass (NWG) in similar to 10 degrees mol dm(-3) acidic solutions below 100 degrees C, where a borosilicate-based glass matrix has been believed to be chemically durable. Most elements like glass main components (Li, B, Na, Ca, Al, and Zn, but except for Si) and simulated radionuclides (Rb, Cs, Sr, Ba, Se, Te, Mn, Pd, Mo, rare earths, Cr, Fe, and Ni) were remarkably eluted from the simulated NWG in similar to 10 degrees M HNO3 aq with Cl- at 90 degrees C. Especially, the elution of Pd is governed by its coordination chemistry including a redox reaction, because Pd(0) present in the simulated NWG has to be oxidized to Pd2+ which forms [PdCl4](2-) for its dissolution. While Zr in simulated NWG is sparingly eluted even in this treatment, its elution actually proceeds in 1-3 M H2SO4 aq at 90 degrees C thanks to strong coordination of Zr(IV) with SO42-. Through design and optimization of the leaching conditions, a protocol of the wet chemical process to retrieve the radionuclides from simulated NWG has been proposed and demonstrated.