Thermal separation of volatile rare isotopes from irradiated target materials

从辐照靶材料中热分离挥发性稀有同位素

• 批准号: SAPIN-2021-00030
• 负责人: Kunz, Peter
• 金额: $ 4.66万
• 依托单位: TRIUMF
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=743106
• 关键词: Thermal; separation; volatile; rare; isotopes

Very promising research on radio-therapeutic methods like radio-immunotherapy, targeted alpha-particle therapy and associated imaging techniques is hampered by the limited availability of extremely rare and relatively short-lived isotopes like 209,211At, 225,226Ac, 223,224Ra , 213Bi or 212Pb. A suitable production method, in particular for isotopes that can't be easily obtained via traditional sources like nuclear reactors or low-energy medical cyclotrons, is provided by ISOL (Isotope Separation OnLine) facilities like TRIUMF/ISAC (Isotope Separation and ACceleration). Even though the main purpose of ISAC is to supply rare isotope beams for research in the fields of nuclear physics and material science, recent efforts to provide samples of 209,211At and 225,226Ac for nuclear medicine research have yielded excellent results. The advantage of the ISOL method is that via the implantation of mass-separated ion beams isotopically and chemically pure samples can be produced. Subsequent, time consuming chemical separation and purification steps are either relatively straightforward or unnecessary. The disadvantage of the method is that the quantities that can be extracted from an ISOL target are limited by target size, low extraction efficiencies and beamtime availability. Therefore, nuclear medicine experiments relying on isotopes from an ISOL source are essentially restricted to basic pre-clinical studies. A major difference between a production target for isotopes with subsequent chemical separation and an ISOL target is their operating temperature. The former is actively cooled, enabling iradiations with high beam intensities, retaining the entire isotope production inventory inside the target. In contrast, ISOL targets are operated at very high temperatures up to 2300 °C to facilitate the fast and efficient release of sufficiently volatile chemical species while the target is irradiated. This proposal aims at research into a combination of both methods, in which a production target made from refractory materials is transferred to a high-temperature vacuum furnace from where fractions of volatile species are extracted from the irradiated target material by diffusion and effusion. It requires the investigation, understanding and subsequent optimization of the thermodynamics and chemistry driving the release and thermo-chromatographic separation of volatile species from a target. This includes development, testing and optimization of suitable experimental setups. One of the two main objectives of the proposal is to find a fast and efficient method for the extraction of the relatively volatile but also short-lived theranostic system 209,211At and its precursor 211Rn. The second main objective is the investigation of thermal separation of Ra and Ac isotopes which are released from actinde carbide targets at much higher temperatures. In the long run, any isotope of interest for harvesting could be investigated.

由于 209,211At、225,226Ac、223,224Ra、213Bi 或 212Pb 等极其稀有且寿命相对较短的同位素的供应有限，对放射治疗方法（如放射免疫疗法、靶向 α 粒子疗法和相关成像技术）的研究非常有前景。一种合适的生产方法，特别是对于无法通过核等传统来源轻松获得的同位素反应堆或低能医用回旋加速器，由 ISOL（在线同位素分离）设施提供，例如 TRUMF/ISAC（同位素分离和加速），尽管 ISAC 的主要目的是为核物理领域的研究提供稀有同位素束。在材料科学领域，最近为核医学研究提供209,211At和225,226Ac样品的努力取得了优异的成果。 ISOL 方法的优点是，通过注入质量分离的离子束，可以产生同位素和化学纯的样品，随后耗时的化学分离和纯化步骤相对简单或不必要。该方法的缺点是数量较多。从 ISOL 靶中提取的同位素受到靶尺寸、低提取效率和波束时间可用性的限制，因此，依赖于 ISOL 源同位素的核医学实验基本上仅限于基础临床前研究。随后进行化学分离的同位素生产目标与 ISOL 目标之间的区别在于，前者是主动冷却的，可以进行高束强度照射，从而将整个同位素生产库存保留在目标内。在高达 2300 °C 的高温下，以促进在靶材受到辐照时快速有效地释放足够挥发性的化学物质。该提案旨在研究两种方法的组合，其中生产靶材由耐火材料被转移到高温真空炉中，通过扩散和流出从受辐照的目标材料中提取挥发性物质的部分，这需要对驱动释放和热色谱的热力学和化学进行研究、理解和后续优化。该提案的两个主要目标之一是找到一种快速有效的方法来提取相对挥发性但寿命较短的物质。治疗诊断系统 209,211At 及其前体 211Rn 的第二个主要目标是研究在更高温度下从锕碳化物靶中释放的 Ra 和 Ac 同位素。从长远来看，可以研究任何感兴趣的收获同位素。 。