In order to investigate phase change and chemical stability of pyrochlore Gd2Zr2O7 used for immobilizing Pu(Ⅳ), tetravalent cerium is used as the simulacrums for plutonium with tetravalence, and Gd2Zr2-xCexO7(0≤ x≤ 2.0) series samples are successfully synthesized by high temperature solid reaction and using Gd2O3 and ZrO2 powders as starting materials. The experiments of long-term chemical stability are conducted in synthetic seawater at 40 °C and 70 °C separately. The XRD diffractive data and extraction ratio of as-gained samples are collected by the help of X-ray diffraction (XRD) instrument and inductively coupled plasma mass spectrometry. The results indicate that the phases of compounds change from pyrochlore to fluorite-type phase when the value of x is more than 0.08. Extraction ratios of Gd3+, Zr4+ and Ce4+ in waste forms increase with the increase of immersion time in synthetic seawater. The extraction ratio of waste form at 70 °C is higher than at 40 °C. The highest extraction ratios of Gd3+, Zr4+ and Ce4+ for 42 days are no more than 0.032, 0.003 and 0.032 μg·ml-1 respectively.

In order to investigate the capability of Gd2Zr2O7 pyrochlore as a waste form for immobilizing trivalent actinides nuclides, Nd(Ⅲ) is used as an alternative substance for An(Ⅲ). The compounds in the system Gd2-xNdxZr2O7 (0≤ x ≤ 2.0) are synthesized at 1500 ℃ for 72 h by high temperature solid state reaction method, using Gd2O3 and ZrO2 powders as the raw materials. The phase, intensity, Vickers hardness and microcosmic shape are characterized by X-ray diffraction, Vickers hardness tester, scanning electron microscopy and so on. The results indicate that the phase of synthesized waste form with plate-shape keeps the phase of pyrochlore. The intensity of compound slightly decreases with the increase of the containment capacity value x, but it is above 5.76 g·cm-3. The value of Vickers hardness also decreases with the increase of x. The values of x and Vickers hardness are linearly related by HV=695.18636-162.64091 x (HV≥ 400 kg·mm-2).