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

塞拉菲尔德核电站自1950年代以来一直在运营，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，清空乏核燃料池，以及储存废物，等待长期处置。塞拉菲尔德核电站一个备受关注的乏核燃料池是第一代Magnox储存池(FGMSP)。这个池塘包含各种各样的废物清单，包括乏燃料、腐蚀的Magnox污泥和无关的环境输入。最近的研究表明，在FGMSP的地表水中存在大量能够存活的微生物。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。微生物也可能会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质被称为胶体。虽然这些过程是众所周知的，但在FGMSP等乏核燃料池中观察到的高pH值条件下，很少有人对这些过程进行调查。这项研究的目的是确定池塘系统中存在的微生物，从好氧的地表水到池塘底部积累的潜在缺氧污泥环境。为此，将收集污泥和水环境的样本，进行16S rRNA和18S rRNA基因测序，以确定存在的原核生物和真核生物及其相对丰度，并酌情使用元基因组学技术。还将通过建立微型实验室实验和使用各种技术和模型来确定微生物过程对关键放射性核素物种形成的影响，从而调查关键放射性核素与微生物的相互作用。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分析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相关的条件下调查这些生物地球化学过程将有助于洞察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去向，所有这些都对Sellafield的池塘运营、回收和处置操作具有影响。目的和目标本项目的总体目标是更好地了解FGMSP中发生的生物地球化学过程。本项目的主要目标有三个：1.确定FGMSP厌氧环境和污泥中有哪些微生物定植。FGMSP的水和污泥样本将被收集。DNA提取后，将进行16S和18S rRNA测序，以鉴定存在的原核和真核生物，并适当应用元基因组学工具。微生物图谱将与地球化学测量结果进行比较，以帮助解释微生物的过程。以确定特定放射性核素在这些微生物存在时的命运。将建立微型实验，接种与FGMSP中发现的微生物类似的微生物，并在添加了关键放射性核素的一系列生物地球化学条件下进行培养。将审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)。将使用的技术包括对预期反应进行模拟的电感耦合等离子体质谱/IC/EXAFS/EM/PHREEQC。确定FGMSP中存在的关键生物矿物，以及这些矿物与可能改变放射性核素形态和流动性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。考虑到与处理这些样品相关的挑战，并行工作将侧重于使用上述技术分析微宇宙孵化过程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.