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

塞拉菲尔德核电站自20世纪50年代以来一直在运行，最近已从发电和燃料后处理过渡到退役。退役涉及拆除设施、清空乏核燃料池和储存废物以待长期处置。塞拉菲尔德核电站的一个乏燃料池是第一代镁诺克斯储存池（FGMSP）。该池塘包含各种废物，包括乏燃料、腐蚀的镁诺克斯污泥和外来环境投入。最近的研究表明，FGMSP的表面沃茨中存在大量能够存活的微生物。已知微生物会影响放射性核素的形态形成，从而导致迁移率的变化。微生物也可能影响放射性核素的流动性，因为含有放射性核素的生物矿物（称为胶体）沉淀。虽然这些过程是众所周知的，但很少进行调查以研究在乏核燃料池（如FGMSP）中观察到的高pH值下的这些过程。本研究的目的是确定存在于池塘系统中的微生物，从好氧表面沃茨到潜在的缺氧污泥环境，已积累在池塘的基础。这将通过收集污泥和水环境的样本并进行16 S rRNA和18 S rRNA基因测序来完成，以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。还将研究关键放射性核素与微生物的相互作用，为此将建立微观实验室规模的实验室实验，并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形态形成的影响。将对含放射性核素的生物矿物的形成进行检查，并使用一系列成像和光谱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相关的条件下研究这些生物地球化学过程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归宿，所有这些都对塞拉菲尔德的池塘作业、回收和处置作业有影响。目的和目标本项目的总体目标是更好地了解FGMSP中发生的地球化学过程。该项目的主要目标有三个：1。确定哪些微生物在FGMSP中的厌氧环境和污泥中定殖。将从FGMSP收集水和污泥样品。DNA提取后，将进行16 S和18 S rRNA测序，以鉴定存在的原核和真核生物，并酌情应用宏基因组学工具。微生物剖面将与地球化学测量结果进行比较，以帮助解释微生物过程。确定特定放射性核素在这些微生物存在下的命运。将建立接种与FGMSP中发现的微生物相似的微生物的微宇宙实验，并在添加关键放射性核素的一系列生物地球化学条件下培养。将检查关键放射性核素的形态，并观察任何矿物的形成（见目标3）。使用的技术将包括ICP-MS/IC/EXAFS/EM/PHREEQC，以模拟预期反应。确定FGMSP中存在的关键生物矿物以及这些生物矿物与可能改变放射性核素形态和迁移率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品，并确定存在的任何关键矿物质。考虑到处理这些样品的挑战，平行工作将侧重于使用上述技术分析矿物相和来自微宇宙培养的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.