Odoh Samuel O, Shamblin Jacob, Colla Christopher A, Hickam Sarah, Lobeck Haylie L, Lopez Rachel A K, Olds Travis, Szymanowski Jennifer E S, Sigmon Ginger E, Neuefeind Joerg, Casey William H, Lang Maik, Gagliardi Laura, Burns Peter C
University of Minnesota , Department of Chemistry, Minnesota Supercomputing Institute, Minneapolis, Minnesota 55455, United States.
Department of Nuclear Engineering, University of Tennessee , Knoxville, Tennesee 37996, United States.
Inorg Chem. 2016 Apr 4;55(7):3541-6. doi: 10.1021/acs.inorgchem.6b00017. Epub 2016 Mar 14.
Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western U.S.A. The drums contained an X-ray amorphous reactive form of uranium oxide that may have contributed to the pressurization. Heating hydrated uranyl peroxides produced during in situ mining can produce an amorphous compound, as shown by X-ray powder diffraction of material from impacted drums. Subsequently, studtite, (UO2)(O2)(H2O)22, was heated in the laboratory. Its thermal decomposition produced a hygroscopic anhydrous uranyl peroxide that reacts with water to release O2 gas and form metaschoepite, a uranyl-oxide hydrate. Quantum chemical calculations indicate that the most stable U2O7 conformer consists of two bent (UO2)(2+) uranyl ions bridged by a peroxide group bidentate and parallel to each uranyl ion, and a μ2-O atom, resulting in charge neutrality. A pair distribution function from neutron total scattering supports this structural model, as do (1)H- and (17)O-nuclear magnetic resonance spectra. The reactivity of U2O7 in water and with water in air is higher than that of other uranium oxides, and this can be both hazardous and potentially advantageous in the nuclear fuel cycle.
近期，美国西部生产的铀黄饼桶发生增压事件，导致工人受伤和放射性污染。这些桶中含有一种X射线非晶态的活性氧化铀形式，可能是导致增压的原因。如对受影响桶中材料的X射线粉末衍射所示，原地开采过程中产生的水合过氧化铀酰加热后可生成一种非晶态化合物。随后，在实验室中对水合过氧化铀酰（(UO2)(O2)(H2O)22）进行加热。其热分解产生一种吸湿的无水过氧化铀酰，它与水反应释放出氧气并形成水合铀酰氧化物——水铀矿。量子化学计算表明，最稳定的U2O7构象异构体由两个弯曲的（UO2）(2+)铀酰离子组成，它们由一个过氧基团双齿桥连且与每个铀酰离子平行，还有一个μ2 - O原子，从而实现电荷中性。中子全散射的对分布函数以及（1）H和（17）O核磁共振谱都支持这一结构模型。U2O7在水中以及在空气中与水的反应活性高于其他铀氧化物，这在核燃料循环中既可能具有危险性，也可能具有潜在优势。
