Metagenomic analysis of open-air and indoor spent fuel storage ponds at Sellafield, UK

Abstract

Nuclear power is an important energy source that can compensate for carbon emissions from fossil fuel power plants. However, processing of radioactive waste from nuclear plants is a significant challenge. The current treatment prior to final geological disposal involves wet storage of spent fuel in designated ponds, and microbial colonisation of these ponds can complicate plant operation. To help identify the key microbes that colonise hydraulically interlinked spent fuel storage ponds at Sellafield, UK, a series of samples were collected and analysed using next generation (Illumina) sequencing. Samples were taken from the facility’s indoor Fuel Handling Plant (FHP) pond (feeding head tank, main and subponds), and also from the open-air First Generation Magnox Storage Pond (FGMSP). 16S rRNA gene sequencing revealed that the FHP is colonized mainly by Bacteria (99%), affiliated with species of Curvibacter, Rhodoferax, Sphingomonas and Roseococcus, in addition to the hydrogen-oxidising bacterium Hydrogenophaga. In contrast the open-air FGSMP pond contained species of Hydrogenophaga, Nevskia, and Roseococcus, and also photosynthetic cyanobacteria (Pseudanabaena). Biological function was also assessed by metagenomic sequencing and analyses. The most abundant genes were associated with carbohydrate and protein metabolism, cell wall and capsule synthesis, stress responses and respiration. Genes involved in respiration were also more abundant in the indoor pond microbiome, including genes underpinning hydrogen metabolism, whilst photosynthesis genes were more abundant in the open-air ponds. These datasets give valuable insight into the microbial communities inhabiting nuclear storage facilities, the metabolic processes that underpin their colonisation and can help inform appropriate control strategies.