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In inactive glasses used as models for French nuclear waste forms, Zr K-and L 2,3 -edge X-ray absorption spectroscopy spectra indicate that Zr is only 6-coordinated, with d(Zr-O) distances of 2.08 ± 0.01 Å and with a small radial disorder. Beyond, the first coordination shell, next-nearest Si neighbors occur at about 3.4 Å. These distances exclude the presence of [7] Zr and/or [8] Zr and suggest [6] Zr-O-Si angles close to 130°, indicating corner-shared ZrO 6 and SiO 4 polyhedra. This structural configuration is similar to those observed in some crystalline zirconosilicates and is in agreement with the stability of Zr in borosilicate melts and glasses.

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