Confidence in copper coating

Above: NWMO corrosion scientists Dr Mehran Behazin and Dr Jeffrey Binns pose with a section of a prototype of the copper-coated used nuclear fuel container (Photo credit: NWMO)

CANADA’S NUCLEAR WASTE MANAGEMENT ORGANIZATION (NWMO) investigated copper as a additional barrier to contain spent nuclear fuel and the scientists’ work — recently published in an international journal — demonstrates that a copper coating is an effective barrier to safely contain used nuclear fuel and can “withstand even the harshest conditions” that may be present inside a deep geological repository in Canada.

The article — “An Evaluation of Corrosion Processes Affecting Copper-Coated Nuclear Waste Containers in a Deep Geological Repository” — was published by Progress in Materials Science. Its findings confirm that the copper coating on an NWMO-designed container for used nuclear fuel is robust and thick enough to withstand any corrosive effects for over a million years.

The copper-coated container is one of five barriers — fuel pellet, fuel assembly, container, Bentonite clay and geology — that will ensure a deep geological repository can safely contain and isolate radioactive material for hundreds of thousands of years.

Above: Copper-coated container for used nuclear fuel (Photo credit: NWMO)

Derek Wilson, NWMO chief engineer and vice-president, contract management, said publication was a testament to the high-quality work being produced by NWMO specialists and added, “The article’s findings also underscore that the proposed repository design will withstand even the harshest conditions to ensure that people and the environment are protected for generations to come.”

The paper reviewed hundreds of research articles relevant to the long-term integrity of copper coatings, spanning nearly a century of peer-reviewed scientific publications.

It serves both as evidence of the safety of the design for Canada’s plan and to inform similar international projects that rely on copper, but with different geospheres, container designs and nuclear materials.

The article reviews past research to calculate what level of corrosion is possible in a repository environment. Also examined are a myriad of possible corrosive factors, such as exposure to groundwater and the potential influence of microbial communities.

The NWMO’s design calls for a 3mm copper coating on the used fuel container.

“This paper shows that we can reasonably expect about 0.25mm of corrosion to occur over a million years. Even if you conservatively presume a series of unlikely events, the total damage will be less than 1.25mm,” said Dr. Peter Keech, manager of engineered barrier science at the NWMO and the article’s senior author. “When we consider that the reference thickness of the copper coating is 3mm, it is clear that we can depend on the container to safely isolate the used nuclear fuel from people and the environment, as part of a multiple barrier system, even as we account for corrosion.”

The article was co-authored by NWMO corrosion scientists Dr Mehran Behazin and Dr Jeffrey Binns, as well as frequent NWMO collaborator and contractor, Dr David S. Hall, who is currently managing a research consortium across the United Kingdom from the University of Cambridge.