As we move towards a greener future, nuclear power is considered a viable energy alternative because it does not produce greenhouse gases. However, its use has created a new problem: how should we safely store radioactive waste?
Used nuclear fuel must be stored for approximately a million years, reducing radioactivity levels to those associated with naturally occurring uranium ore. A commonly proposed storage solution is to bury the waste for long-term safekeeping in underground sites known as deep geological repositories (DGRs), but more research needs to be done to finalize a safe and durable design.
Professor Josh Neufeld and his laboratory are part of a multi-institutional collaboration to study microbial communities that inhabit subsurface rock and water at the proposed 500 metre repository depth, and those that might grow in the engineered barrier components that will surround the used fuel containers. This collaboration, which has just received new Alliance Grant funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), also includes researchers from the University of Toronto and McMaster University, and their industry partner the Nuclear Waste Management Organization (NWMO).
The researchers in this collaboration will explore microbial communities and associated natural organic matter profiles from subsurface rock and groundwater samples, an important step in building a safety case for a potential repository site. Experiments using proposed barrier components of the repository, such as bentonite clay, will help determine the possibility of microbial growth and activity under the expected conditions. Naturally occurring rock and water samples from locations and sites with similar geology to the proposed repository will also be studied to better predict the long-term stability and activity of microorganisms. Of particular concern are microorganisms that produce sulfide which could corrode the used fuel containers, or gases which could create pathways for subsurface microbes and metabolites to access the fuel containers.
Professor Neufeld’s laboratory in the University of Waterloo's Department of Biology uses a variety of microbiology techniques, including cultivating microbes and DNA sequencing, to quantify and profile microorganisms in samples associated with this project. In particular, his research team is well equipped to handle environmental samples with very low numbers of microbes, which can approach the limits of detection. His laboratory has been involved in three prior research partnerships with the NWMO since 2016, including one project featuring graduate student Rachel Beaver that was highlighted recently.
“This NSERC Alliance Grant will enable a unique collaboration among several laboratories. We will use complementary techniques to shed light on the microbial communities associated with subsurface samples and engineered barrier components of a deep geological repository,” explains Professor Neufeld, who is responsible for the project’s overall direction.
Professor Greg Slater of McMaster University has worked extensively over the past 20 years developing and applying new approaches to understand the fate and transport of organic compounds in environmental systems, including a focus on the characterization of microbial biomarkers, such as membrane lipids, from various environments. His laboratory will analyze lipid profiles for subsurface samples and experiments to complement the DNA-based and cultivation approaches used by the University of Waterloo.
Professor Myrna Simpson, the Tier 1 Canada Research Chair in Integrative Molecular Biogeochemistry at the University of Toronto, is an expert on natural organic matter chemistry and reactivity in terrestrial and aquatic environments. Her laboratory explores how organic matter serves as a microbial growth substrate in various environments, using nuclear magnetic resonance and mass spectrometric techniques for her analytical work. For the NSERC Alliance research, the molecular-level organic matter data from Professor Simpson’s laboratory will provide unique metabolic insight into what the microorganisms in these samples are capable of consuming and producing as they grow.
“We are grateful for this timely opportunity to ensure that microbiology data will inform the NWMO as it identifies a suitable host site for a Canadian DGR and builds a safety case to ensure a stable repository," says Neufeld. "Specifically, our project will test various factors, such as temperature, salinity, and moisture, to ensure that specifications for a DGR will prevent microbial growth and activity over geological timeframes.”
The NSERC Alliance Grant is a five year grant with the purpose of encouraging university researchers to collaborate with partner organizations in order to accelerate the application of research results across Canada. The funding awarded to Neufeld and his collaborators has a total budget of approximately $2.8 million, and the University of Waterloo is the home institution for this project. Together, this team will work to characterize the impact of microbial activity on the proposed deep geological repository in order to contribute to the overall assessment of the safety of these repositories for permanent nuclear waste storage.