Microbe - radionuclide interactions in legacy nuclear waste systems (EPSRC iCASE)

Sellafield工厂自20世纪50年代开始运营，最近从电力生产和燃料后处理过渡到退役。退役包括拆除设施、清空乏燃料池和储存等待长期处置的废料。在塞拉菲尔德场址引起强烈关注的一个乏燃料池是第一代镁诺克斯储存池（FGMSP）。这个池塘包含各种各样的废物，包括乏燃料、腐蚀的镁诺克斯污泥和外来的环境输入。最近的研究表明，在FGMSP的地表水中存在多种能够生存的微生物。众所周知，微生物会影响放射性核素的形态，从而导致流动性的变化。微生物也可能影响放射性核素的流动性，因为含有生物矿物质的放射性核素被称为胶体的沉淀。虽然这些过程是众所周知的，但在FGMSP等乏燃料池中观察到的高pH值下对这些过程进行的调查很少。本研究旨在确定池塘系统中存在的微生物，从好氧地表水到池塘底部积累的潜在缺氧污泥环境。这将通过收集污泥和水环境样本并进行16S rRNA和18S rRNA基因测序来确定存在的原核和真核生物及其相对丰度，并酌情使用宏基因组技术来完成。关键放射性核素与微生物的相互作用也将通过建立微观尺度的实验室实验和使用各种技术和建模来确定微生物过程对关键放射性核素物种形成的影响来进行调查。将对含有放射性核素的生物矿物的形成进行检查，并将利用一系列成像和光谱学技术进一步研究微生物在其形成和稳定性中的作用。在与FGMSP相关的条件下对这些生物地球化学过程进行调查，将有助于了解池塘中微生物的生存机制和池塘系统中关键放射性核素的命运，所有这些都对Sellafield的池塘操作、回收和处置操作具有重要意义。目的和目标该项目的总体目标是对FGMSP中发生的生物地球化学过程有更深入的了解。这个项目有三个主要目标：1。确定哪些微生物在FGMSP的厌氧环境和污泥中定植。将收集FGMSP的水和污泥样本。DNA提取后，将进行16S和18S rRNA测序，以鉴定存在的原核生物和真核生物，并酌情使用宏基因组工具。微生物剖面将与地球化学测量相比较，以帮助解释微生物过程。在这些微生物存在的情况下确定特定放射性核素的命运。用与FGMSP中发现的微生物相似的微生物接种，在一系列生物地球化学条件下建立微观实验，并添加关键放射性核素。将检查一种关键放射性核素的形态，并观察任何矿物的形成（见目标3）。将使用的技术包括ICP-MS/IC/EXAFS/EM/PHREEQC来模拟预期的反应。确定FGMSP中存在的关键生物矿物及其与可能改变放射性核素形态和迁移的关键放射性核素的相互作用。理想情况下，我们希望收集水和污泥样本，并确定存在的任何关键矿物质。考虑到与处理这些样品相关的挑战，平行工作将集中在使用上述技术分析微观培养皿中的矿物相和放射性核素相互作用。

The Sellafield site has been in operation since the 1950s and has recently transitioned from power production and fuel reprocessing to decommissioning. Decommissioning involves dismantling facilities, emptying spent nuclear fuel ponds and storage of wastes pending long term disposal. One spent nuclear fuel pond of intense concern at the Sellafield site is the First Generation Magnox Storage Pond (FGMSP). This pond contains a diverse inventory of waste including spent fuel, corroded Magnox sludge and extraneous environmental inputs. Recent studies have shown the presence of a broad range of microorganisms capable of surviving in the surface waters of the FGMSP. Microorganisms are known to affect the speciation of radionuclides resulting in changes in mobility. Microbes may also affect the mobility of radionuclides due to the precipitation of radionuclide containing biominerals known as colloids. While these processes are well-known, little investigation has been conducted to investigate these processes at the high pH values observed in spent nuclear fuel ponds such as the FGMSP. This study will aim to identify the microorganisms present in the pond system, from aerobic surface waters into the potentially anoxic sludge environment that has accumulated at the base of the pond. This will be done by collecting samples of the sludge and water environments and carrying out 16S rRNA and 18S rRNA gene sequencing to identify the prokaryotic and eukaryotic organisms present and their relative abundances and use metagenomic techniques as appropriate. The interactions of key radionuclides with microorganisms will also be investigated by setting up microcosm scale laboratory experiments and using a variety of techniques and modelling to identify the impact of microbial processes on key radionuclide speciation. Examination of the formation of radionuclide containing biominerals will be conducted and further investigation into the role of microbes in their formation and stability will be explored using a range of imaging and spectroscopy techniques.Investigation into these biogeochemical processes under conditions relevant to the FGMSP will provide insight to the survival mechanisms of microorganisms in the ponds and the fate of key radionuclides in the pond system, all of which have implications for pond operation, retrieval and disposal operations at Sellafield.Aims and objectivesThe overall aim of this project is to gain a greater understanding of the biogeochemical processes occurring in the FGMSP. There are 3 main objectives of this project: 1. To determine what microorganisms colonise the anaerobic environment and sludge in the FGMSP. Water and sludge samples from the FGMSP will be collected. After DNA extraction, both 16S and 18S rRNA sequencing will be carried out to identify the prokaryotic and eukaryotic organisms present, with metagenomic tools applied as appropriate. Microbial profiles will be compared to geochemical measurements to help interpret microbial processes.2. To determine the fate of specific radionuclides in the presence of these microorganisms. Microcosm experiments inoculated with microbes similar to those found in FGMSP will be set up and incubated under a range of biogeochemical conditions with key radionuclides added. The speciation of a key radionuclides will be examined and the formation of any minerals will be observed (see objective 3). Techniques to be used will include ICP-MS/IC/EXAFS/EM/PHREEQC to model expected reactions.3. To identify the key biominerals present in the FGMSP and the interactions of these with key radionuclides which may alter radionuclide speciation and mobility. Ideally, we hope to collect water and sludge samples and identify any key minerals present. Given the challenges associated with handling these samples, parallel work will focus on the analysis of mineral phases and radionuclide interactions from microcosm incubations using the techniques above.