Speaker
Description
Uranium mining and milling activities contribute to the release of natural uranium and its decay products into the environment. This may lead to potential radiological risks. While U-238 and its decay products are routinely monitored, the behaviour of the U-235 decay products is either not considered, or only estimated based on the U-238 decay chain in radiological assessments [1].
Pa-231 is one of the few long-lived isotopes in the U-235 decay chain. It has a half-life of 3∙10^5 years and lacks analogues in the U-238 decay series. Hence, it is necessary to study Pa-231 to learn about the transport and possible accumulation of U-235 decay products in the environment that might differ from the U-238 decay series [2].
In this talk, I will present two different approaches to studying the behaviour of Pa-231 in the environment. First, we use the short-lived isotope Pa-233 (half-life 27 days) as an analogue to study the interaction of Pa with plants. Using gamma spectroscopy and autoradiography, we provide an insight into the translocation and accumulation patters of Pa in Sand Oat (Avena strigosa).
To check if the results from the Pa-233 experiments are transferable to real life environmental situations we are planning to measure Pa-231 in the environment using Accelerator Mass Spectrometry (AMS). This ultra-sensitive method is capable of measuring minute concentrations of long-lived radionuclides. Especially actinides can be measured to unparalleled sensitivity. The measurement of Pa-231 is not yet an established procedure at most AMS laboratories, but there are multiple ongoing efforts to develop such a procedure [2,3]. The main challenges are the complications in chemical sample preparation, particularly Pa losses due to sorption on lab equipment.
We have developed and adapted chemical sample preparation procedures for multiple environmental samples including water from a uranium mine, riverbank soil and plants. First, the Pa is leached from each environmental sample using a specific protocol. Then, Pa needs to be separated from the environmental matrix, where each sample material comes with its own challenges. I will give an overview of different leaching mechanisms and elemental separation methods we tested for separating Pa from environmental samples, focussing on where we lose Pa in the sample preparation and how to avoid these losses.
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[1] Beaugelin-Seiller, K., et al., J. Environ. Radioact., 2016, 151, 114-125.
[2] Medley, P., et al., Nucl. Instrum. Methods Phys. Res. B, 2019, 438, 66-69.
[3] Christl, M., et al., Nucl. Instrum. Methods Phys. Res. B, 2007, 262, 379-284.
| Student Submission | Yes |
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