Epsilon metal (ε-metal) is the metallic phase that forms as inclusions at the grain boundaries in the UO₂ fuel during reactor operation. This metal is composed of Pd, Mo, Rh, Ru, and Tc. These metallic inclusions are insoluble in strong acid and remnants of these metallic inclusions have been found in the UO₂ matrix that remains from the natural reactors in Gabon that were active 1.8 billion years ago, therefore ε-metal should be an excellent waste form for the immobilization of the long-lived isotopes ¹⁰⁷Pd (6.5 × 10⁶ a) and ⁹⁹Tc (2.13 × 10⁵ a), with ⁹⁹Tc being the isotope of interest for repository performance. Therefore, the chemical durability of this potential waste form is assessed in this study. Typically, corrosion rates for metallic materials are measured electrochemically because they are quick, inexpensive, and can reveal the mechanism by which a metal corrodes, at least initially. However, in a repository the waste form would be subjected to slowly flowing water without an applied electrical potential over long time periods. Therefore, the corrosion rates of ε-metal specimens were measured with both electrochemical tests and the single-pass flow-through test (SPFT). Potentiodynamic and potentiostatic polarization results suggest that a thin passive film exists on the alloy surface, which seems to be responsible for its high corrosion resistance. Additionally, X-Ray photoelectron spectroscopic results suggest that Pd oxides are significantly enriched in the passive film Results from the SPFT show that the dissolution rates were weakly dependent on pH. Only Mo and Re were found in solution and were used for the calculation of the dissolution rates. In general, the electrochemically determined corrosion rates agree reasonably well with the initial dissolution rate measured with the SPFT test, but they are about one or two orders of magnitude higher than the steady state rates. The causes for this discrepancy are discussed.

Epsilon金属（ε-金属）是在反应堆运行期间在UO ₂燃料的晶界处形成为夹杂物的金属相。该金属由Pd，Mo，Rh，Ru和Tc组成。这些金属夹杂物不溶于强酸，这些金属夹杂物的残留物存在于18亿年前活跃于加蓬的天然反应堆中的UO ₂基质中，因此ε-金属应是一种极好的废料形式。固定长寿命同位素¹⁰⁷ Pd（6.5×10 ⁶ a）和⁹⁹ Tc（2.13×10 ⁵ a），其中⁹⁹Tc是存储库性能感兴趣的同位素。因此，这项研究评估了这种潜在废物形式的化学耐久性。通常，对金属材料的腐蚀速率是通过电化学方法测量的，因为它们快速，廉价，并且可以揭示金属腐蚀的机理，至少在最初是这样。但是，在储存库中，废物形式将长时间处于缓慢流动的水中而没有施加电势。因此，通过电化学测试和单次通过测试（SPFT）来测量ε-金属样品的腐蚀速率。电位动力学和恒电位极化结果表明，合金表面上存在薄的钝化膜，这似乎是其高耐腐蚀性的原因。另外，X射线光电子能谱结果表明，钝化膜中Pd氧化物明显富集。SPFT结果表明，溶出速率对pH的依赖性很小。在溶液中仅发现Mo和Re，并用于计算溶出度。通常，电化学测定的腐蚀速率与用SPFT测试测得的初始溶解速率相当吻合，但它们比稳态速率高大约一个或两个数量级。讨论了这种差异的原因。电化学测定的腐蚀速率与SPFT测试测得的初始溶解速率相当吻合，但比稳态速率高大约一个或两个数量级。讨论了这种差异的原因。电化学测定的腐蚀速率与SPFT测试测得的初始溶解速率相当吻合，但比稳态速率高大约一个或两个数量级。讨论了这种差异的原因。