National Nuclear Laboratory


Saturday 24 February 2018

NNL reviews Canada’s microbiologically influenced corrosion research program

CANDU 1.pngNNL expertise has been harnessed in a new contract with Canada’s Nuclear Waste Management Organization (NWMO), the organisation responsible for designing and implementing Canada’s plan for the safe, long-term management of spent nuclear fuel. The new contract is for NNL is to carry out an expert peer review of Canadian academic research, supported by NWMO, to assess the potential for microbiologically influenced corrosion (MIC) of canisters that will be used to dispose of spent nuclear fuel in a future geological disposal facility.In 2014, Canada developed a new spent fuel canister that has 3 mm of copper applied directly by electrodeposition and cold spray onto a steel container that will hold 48 nuclear waste bundles from their Canadian Deuterium Uranium (CANDU) nuclear reactors (Figure 1). Previous designs involved an inner steel vessel surrounded by a wrought copper shell. The new Canadian design offers improved protection against mechanical performance problems related to structural loading that can cause wrought copper shells to deform. The steel container and its spherical head are designed to have the mechanical strength needed to withstand pressures of the overlying rock and loading from a 3-km thick glacier in the event of a future Canadian ice age. The spent fuel canister is part of an engineered barrier system that must isolate the fuel for hundreds of thousands of years.The copper coating is designed to protect the canister from corrosion. Under anoxic conditions, sulphate-reducing bacteria have the potential to produce sulphide, which can cause MIC. It is therefore essential for waste management organisations and regulators understand the levels of sulphide that will be present in the geological disposal facility, to understand its potential to migrate to the canister surface and the potential for it to cause copper corrosion. Since sulphate-reducing bacteria, that will be present in the facility, will affect the levels of sulphide present, NWMO has been actively developing computer models that will be used to evaluate the potential for MIC once a disposal site has been selected.The awarding of the peer review contract to assess NWMO MIC program was the result of NNL’s expertise in the biogeochemical processes that could affect repository performance and in developing computer modelling techniques that simulate the effects of sulphate-reducing bacteria. The work is linked closely with NNL’s participation in the European Commission Horizon-2020 MIND (Microbiology in Nuclear waste Disposal) project.Dr Liam Abrahamsen-Mills, Senior Research Technologist, is a member of the NNL team working on the review. He said: “We are really pleased to be working with NWMO on improving the understanding of how microbes can influence the complex biogeochemistry of a repository, and ultimately its long-term safety. The contract will run until March 2019 and it is hoped by both parties that this will be the start of an ongoing collaborative relationship.”

“Review of our corrosion research programs by international experts is an important component of our plan to demonstrate the safety of our new canister design concept” said Dr. Jennifer McKelvie, a Senior Scientist at NWMO. “By involving respected researchers, like Dr. Abrahamsen-Mills and Professor Joe Small of NNL, in the peer-review of our program, we are ensuring that our work meets the highest scientific standards and is consistent with international best practice.”

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Figure 1. The Canadian spent nuclear fuel canister, which is designed to contain and isolate nuclear waste in a future geological disposal facility. The canister is 2.5 m long, 0.6 m wide and will weigh approximately 2800 kg when loaded. 

The Canadian Nuclear Waste Management Organisation (NWMO) is responsible for designing and implementing Canada’s plan for the safe, long-term management of used nuclear fuel. The plan, known as Adaptive Phased Management, requires used fuel to be contained and isolated in a deep geological repository. It also calls for a comprehensive process to select an informed and willing host for the project. The NWMO is a not-for profit organisation established in 2002 by Canada’s nuclear electricity producers in accordance with the Nuclear Fuel Waste Act (NFWA).

The MIND project has received funding from the Euratom research and training programme 2014 – 2018 under grant agreement No. 661880.