Altmann Scott
Andra, 1 rue Jean-Monnet, Chatenay-Malabry, 92298, France.
J Contam Hydrol. 2008 Dec 12;102(3-4):174-9. doi: 10.1016/j.jconhyd.2008.09.012. Epub 2008 Oct 15.
Disposal of high level radioactive waste in deep underground repositories has been chosen as solution by several countries. Because of the special status this type waste has in the public mind, national implementation programs typically mobilize massive R&D efforts, last decades and are subject to extremely detailed and critical social-political scrutiny. The culminating argument of each program is a 'Safety Case' for a specific disposal concept containing, among other elements, the results of performance assessment simulations whose object is to model the release of radionuclides to the biosphere. Public and political confidence in performance assessment results (which generally show that radionuclide release will always be at acceptable levels) is based on their confidence in the quality of the scientific understanding in the processes included in the performance assessment model, in particular those governing radionuclide speciation and mass transport in the geological host formation. Geochemistry constitutes a core area of research in this regard. Clay-mineral rich formations are the subjects of advanced radwaste programs in several countries (France, Belgium, Switzerland...), principally because of their very low permeabilities and demonstrated capacities to retard by sorption most radionuclides. Among the key processes which must be represented in performance assessment models are (i) radioelement speciation (redox state, speciation, reactions determining radionuclide solid-solution partitioning) and (ii) diffusion-driven transport. The safety case must therefore demonstrate a detailed understanding of the physical-chemical phenomena governing the effects of these two aspects, for each radionuclide, within the geological barrier system. A wide range of coordinated (and internationally collaborated) research has been, and is being, carried out in order to gain the detailed scientific understanding needed for constructing those parts of the Safety Case supporting how radionuclide transfer is represented in the performance assessment model. The objective here is to illustrate how geochemical research contributes to this process and, above all, to identify a certain number of subjects which should be treated in priority.
几个国家已选择在深层地下处置库中处置高放废物作为解决方案。由于这类废物在公众心目中的特殊地位，国家实施计划通常会动员大规模的研发工作，持续数十年，并受到极其详细和严格的社会政治审查。每个计划的最终论点都是针对特定处置概念的“安全案例”，其中除其他要素外，还包含性能评估模拟的结果，其目的是模拟放射性核素向生物圈的释放。公众和政治对性能评估结果（通常表明放射性核素释放将始终处于可接受水平）的信心基于他们对性能评估模型中所包含过程的科学理解质量的信心，特别是那些控制地质主岩中放射性核素形态和质量传输的过程。地球化学在这方面构成了一个核心研究领域。富含粘土矿物的地层是几个国家（法国、比利时、瑞士等）先进放射性废物计划的研究对象，主要是因为它们的渗透率极低，并且具有通过吸附作用阻滞大多数放射性核素的能力。性能评估模型中必须体现的关键过程包括：（i）放射性元素形态（氧化还原状态、形态、决定放射性核素固 - 溶液分配的反应）和（ii）扩散驱动的传输。因此，安全案例必须证明对地质屏障系统内控制这两个方面对每种放射性核素影响的物理化学现象有详细的了解。为了获得构建安全案例中支持性能评估模型中放射性核素转移表示部分所需的详细科学理解，已经并正在开展广泛的协调（以及国际合作）研究。此处的目的是说明地球化学研究如何促进这一过程，最重要的是，确定一些应优先处理的主题。
