Williams Reid F, Kaplan Daniel I, Erdmann Bryan J, DeVol Timothy A, Powell Brian A
Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, SC, 29625, USA; Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management Center (NEESRWM), Clemson University, Anderson, SC, 29625, USA.
Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29808, USA.
J Environ Radioact. 2024 Dec;280:107527. doi: 10.1016/j.jenvrad.2024.107527. Epub 2024 Sep 7.
Safe and effective storage of radioactive waste is essential to protect human and environmental health. Due to the potential for accidental releases and the severity of the associated risks, it is imperative to further understand radionuclide transport should an accident occur. This study was the second set of measurements conducted in 2022 of an ongoing experiment that has analyzed the vadose zone migration of radionuclides from cementitious wasteforms at the Savannah River Site over the last ten years. The radionuclides introduced within the sources are prominent constituents of radioactive waste or analogs for other groups or series of radionuclides. Lysimeters were first analyzed in 2016 using a collimated high-purity germanium gamma-ray spectrometer to non-destructively measure the concentration of each radionuclide in the sediment column as a function of depth. Following these measurements, the lysimeters were redeployed for another 4 years. All radionuclides in all lysimeters were observed to transport further during the redeployment period; however, the extent of migration varied with the material used for introduction. Except for Cs, migration through the sediment control system increased with decreasing ionic potential (ionic charge/radius); migration order: Eu < Cs < Co < Ba. Overall, the cementitious wasteforms were observed to decrease radionuclide migration extent relative to natural vadose zone conditions. In both cementitious wasteforms, the migration extent increased in the order Eu < Ba<Co < Cs. However, less migration was measured when the radionuclides were incorporated into a reducing grout wasteform. The novelty of this paper is the demonstration of a technique capable of creating non-destructive measurements over decade time scales. Ultimately, this work provides insight into the long-term migration of alkali, alkali earth, divalent transition metal, and trivalent (e.g., lanthanide and actinide element) isotopes.
安全有效地储存放射性废物对于保护人类和环境健康至关重要。由于存在意外释放的可能性以及相关风险的严重性，若发生事故，进一步了解放射性核素的迁移情况势在必行。本研究是2022年对一项正在进行的实验进行的第二轮测量，该实验在过去十年中分析了萨凡纳河场址放射性核素从水泥固化废物形式在包气带中的迁移。源中引入的放射性核素是放射性废物的主要成分或其他组或系列放射性核素的类似物。2016年首次使用准直高纯锗伽马射线光谱仪对渗漏计进行分析，以无损测量沉积物柱中各放射性核素浓度随深度的变化。在这些测量之后，渗漏计又重新部署了4年。在重新部署期间，观察到所有渗漏计中的所有放射性核素都进一步迁移；然而，迁移程度因引入所用的材料而异。除铯外，通过沉积物控制系统的迁移随着离子势（离子电荷/半径）的降低而增加；迁移顺序为：铕＜铯＜钴＜钡。总体而言，相对于天然包气带条件，观察到水泥固化废物形式会降低放射性核素的迁移程度。在两种水泥固化废物形式中，迁移程度按铕＜钡＜钴＜铯的顺序增加。然而，当放射性核素掺入还原性灌浆废物形式时，测量到的迁移较少。本文的新颖之处在于展示了一种能够在十年时间尺度上进行无损测量的技术。最终，这项工作为碱金属、碱土金属、二价过渡金属和三价（例如镧系和锕系元素）同位素的长期迁移提供了见解。
