Exotic radionuclides from Accelerator Waste for Science and Technology - ERAWAST III: Half-life determination of pure electron capture nuclides (La-137, Tb-157)

科技加速器废物中的外来放射性核素 - ERAWAST III：纯电子捕获核素（La-137、Tb-157）的半衰期测定

• 批准号: 450057137
• 负责人: Dr. Karsten Kossert
• 金额: --
• 依托单位: Paul Scherrer Institut (PSI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/450057137?language=en
• 关键词: Exotic; radionuclides; Accelerator; Waste; Science

In two previous projects (ERAWAST I and II) funded by the Swiss National Science Foundation (SNF) it was made clear that the lack of reliable nuclear decay data is astonishingly huge, in particular for half-lives of relatively long-lived radionuclides. In general, half-lives are relevant for applications in nuclear medicine and industry, and several research fields (e.g. environmental and climate research, Earths and Solar sciences) require accurate data.A research group at PSI has gained access to a considerable number of sources for long-lived radionuclides and developed extraordinary experience in radiochemical separation and purification techniques over the last 15 years. Based on this, measurements of several radionuclides were possible and unique results were obtained.With the present proposal (SNF Lead Agency + DFG), we shift the focus to the half-life determination of the first two examples of pure electron capture lanthanide isotopes: 137La and 157Tb. The half-life measurements for these two radionuclides are extremely challenging and strongly depend on the quality of the sample. In particular, samples must not contain any other radiation-emitting isotope and the measurement of the number of atoms requires a reliable method for estimating the contribution of possible isobars. Moreover, transition probabilities and de-excitation spectra shapes of these two isotopes are not well-known, which increases the uncertainty of the activity measurement accordingly. Improvement could be achieved by measuring these spectra with a novel kind of detectors, Magnetic Metallic Calorimeters (MMC), which are currently being explored in several metrology groups. Dedicated sample preparation procedures have to be developed to make this kind of detectors applicable in the future. The following tasks have to be fulfilled:• Purification of the 137La sample, which was obtained in the frame of ERAWAST II.• Separation of 157Tb from irradiated enriched 156Dy. Purification of the sample.• Activity determination using Liquid Scintillation Counting with uncertainty < 5% (to be performed by PTB)• Determination of the number of atoms by ICP-MS with uncertainty < 2%, considering correction of the isobar contribution.• Exploring sample deposition procedures for MMCs.Precision measurements with high accuracy and low uncertainties meet urgent requirements from nuclear data communities, metrology groups and related science. With this two-year program, we hope to pave the way for a long-lasting program for sample preparation and development of front-end measurement techniques for long-lived, “hard-to measure” isotopes after the retirement of the PI (D. Schumann) in 2023.

在瑞士国家科学基金会资助的前两个项目(ERAWAST I和II)中明确指出，缺乏可靠的核衰变数据令人震惊地巨大，特别是相对较长寿命的放射性核素的半衰期。一般来说，半衰期在核医学和工业中的应用是相关的，一些研究领域(如环境和气候研究、地球和太阳科学)需要准确的数据。在过去的15年里，PSI的一个研究小组已经获得了相当多的长寿命放射性核素的来源，并在放射化学分离和纯化技术方面积累了非凡的经验。在此基础上，对几种放射性核素进行了测量，并获得了独特的结果。在本方案中，我们将重点转移到前两个纯电子俘获稀土同位素137La和157Tb的半衰期测定上。这两种放射性核素的半衰期测量极具挑战性，并且在很大程度上取决于样品的质量。特别是，样品不得含有任何其他发射辐射的同位素，测量原子数量需要一种可靠的方法来估计可能的同量异位素的贡献。此外，这两种同位素的跃迁几率和去激发谱形状都不为人所知，这就增加了活度测量的不确定性。通过使用一种新型的探测器--磁性金属量热计(MMC)来测量这些光谱，可以获得改进，目前几个计量学小组正在探索这种探测器。必须开发专门的样品制备程序，以使这种检测器在未来得到应用。·提纯在ERAWAST II框架下获得的~(137)La样品。·从辐照浓缩物~(156)Dy中分离~(157)Tb。·使用液体闪烁计数法测定活度，不确定度为5%(由PTB执行)·考虑到等压素贡献的校正，通过电感耦合等离子体质谱仪测定原子数目，不确定度为2%。·探索MMC的样品沉积程序。高精度和低不确定度的精确测量满足核数据界、计量组和相关科学的迫切要求。通过这项为期两年的计划，我们希望为2023年PI(D.Schumann)退休后为样品制备和开发长寿命、难以测量的同位素的前端测量技术的长期计划铺平道路。