A bench-top type ultracentrifuge to secure the reliability of safety assessment of used nuclear fuel disposal

确保废核燃料处置安全评估可靠性的台式超速离心机

• 批准号: RTI-2019-00733
• 负责人: Nagasaki, Shinya
• 金额: $ 7.61万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=660587
• 关键词: bench; top; type; ultracentrifuge; secure

In this NSERC RTI Grant, a bench-top type ultracentrifuge is required. This is a critical tool to measure the values of sorption distribution coefficient (Kd) of elements which dominate the long-term risk of used nuclear fuel disposal.*** Since the migration of elements in the repository, the geosphere and the biosphere is assessed by their Kd values, the ability to reliably measure these values is critical in the safety assessment of disposal. Furthermore, the sensitivity analysis on the safety assessment by the Nuclear Waste Management Organization (NWMO), the Japan Atomic Energy Agency and other institutes shows that the uncertainty of the Kd value significantly and directly affects the result of safety assessment. *** Five municipalities in Ontario are under review for the site selection of used nuclear fuel repository by the NWMO. Three are the crystalline rock media and two are the sedimentary rock media. The unique feature of groundwater in these areas is the high ionic strength (saline and brine). Even when the rocks and the bentonite (a candidate material for engineered barrier in Canada) contact saline and brine, small particles (about 2.5 nm to several tens nm) are released into the solution. One of the most critical factors to measure the reliable Kd values is how completely we can separate the liquid from the solid including the small particles. The ultracentrifugation is the only way to separate such small particles from liquid phase, and is a global standard method to measure the reliable Kd values. Incomplete separation of small particles leads to large uncertainties of Kd values.*** The NWMO plans to select one municipality to host the repository in 2023, and to submit the Environmental Assessment and Licence application to the Federal Government in 2028. This means that the reliable Kd values have to be measured as soon as possible, and are essential to protect our health and environment and to improve our confidence in the used nuclear fuel disposal in Canada.*** The bench-top type ultracentrifuge requested in this grant will be used in the research funded by the NWMO. Because of the bench-top type, it can be installed in a glove box in which the atmosphere is strictly controlled to achieve the experimental conditions equivalent to deep geological media in Ontario. The Kd values of Se, Tc and Np on Canadian rocks in saline and brine under the reducing and oxidizing conditions will be measured, and will be compiled in the NWMO Sorption Database. Furthermore, the NWMO lists 19 elements of interest which are important in the safety assessment, and only few works on their sorption in saline and brine under the reducing conditions have been conducted. McMaster University is the only institute in Canada where the sorption behaviours of the important elements can be studied, and so the opportunity to use the ultracentrifuge will certainly be expanded in future works including NSERC Discovery Grant applied for now.

在本次 NSERC RTI 资助中，需要一台台式超速离心机。这是测量主导废核燃料处置长期风险的元素吸附分布系数 (Kd) 值的关键工具。*** 由于对储存库、地质圈和生物圈中元素的迁移进行了评估根据其 Kd 值，可靠测量这些值的能力对于处置安全评估至关重要。此外，核废料管理组织（NWMO）、日本原子能机构等机构对安全评估的敏感性分析表明，Kd值的不确定性显着且直接影响安全评估的结果。 *** NWMO 正在审查安大略省五个市的废核燃料储存库选址。三种是结晶岩介质，两种是沉积岩介质。这些地区地下水的独特之处在于离子强度高（盐水和卤水）。即使当岩石和膨润土（加拿大工程屏障的候选材料）接触盐水和盐水时，小颗粒（约 2.5 nm 至几十 nm）也会释放到溶液中。测量可靠的 Kd 值的最关键因素之一是如何将液体与固体（包括小颗粒）完全分离。超速离心是从液相中分离此类小颗粒的唯一方法，也是测量可靠 Kd 值的全球标准方法。小颗粒分离不完全导致Kd值存在较大不确定性。*** NWMO计划在2023年选择一个城市作为储存库的托管地，并在2028年向联邦政府提交环境评估和许可申请。这意味着必须尽快测量可靠的 Kd 值，这对于保护我们的健康和环境以及提高我们对加拿大废核燃料处理的信心至关重要。*** 本次拨款中要求的台式超速离心机将是用过的NWMO 资助的研究。由于是台式，可以安装在严格控制气氛的手套箱内，达到相当于安大略省深层地质介质的实验条件。将测量还原和氧化条件下加拿大岩石中盐水和盐水中 Se、Tc 和 Np 的 Kd 值，并将其汇总到 NWMO 吸附数据库中。此外，NWMO 列出了 19 种对安全评估很重要的关注元素，但在还原条件下对其在盐水和盐水中的吸附进行了很少的研究。麦克马斯特大学是加拿大唯一可以研究重要元素吸附行为的机构，因此在未来的工作中肯定会扩大使用超速离心机的机会，包括目前申请的 NSERC Discovery Grant。