Building better reactors for a nuclear renaissance

A large steel dome rises overhead – a wide opening at the top letting in sunlight. Halfway to the opening, a star-shaped platform extends a number of long supports to touch the walls in every direction.

Building better reactors for a nuclear renaissance

Queen’s University’s Reactor Materials Testing Laboratory tests the materials used to build nuclear reactors to make them safer and more efficient
September 1, 2015

As large industrial installations go, nuclear reactors may not seem to be all that complicated. Large supports are needed to hold up walls and secure areas where temperature and pressure can build up, and intricate pipes run through the parts where cooling water or fuel is used. But, if all goes well, none of this infrastructure will have to face conditions anything like the extremes found in some major manufacturing facilities. Compared to the fiery heart of a typical steel foundry, for example, the interior of a reactor can look positively serene.

Nevertheless, a reactor core is demanding in one extraordinary respect: it is the site of intense radiation emitted by the fuel source, which is usually uranium.

“You’ve got these high energy particles — neutrons — that are slamming into the structure of all the surrounding material and they generate a lot of damage,” explains Mark Daymond. “That damage then influences the properties of that material, usually in ways that degrade it.”

Daymond holds an Industrial Research Chair in Nuclear Materials at Queen’s University, a post that has given him a unique opportunity to seek better ways of considering radiation’s effects on a reactor core’s structural components. Such progress could make a significant difference to the maintenance schedules and long-term operation of existing reactors, quite possibly reducing their operating costs and extending their working lifetimes.

“From both a financial and environmental perspective, keeping existing reactors going as long as possible makes huge sense,” he says, noting that nuclear power is undergoing an international renaissance in a world looking for a reliable, consistent source of electricity with essentially no carbon dioxide emissions.

Toward that end, Daymond and his colleagues at Queen’s have established a facility that represents a major step forward in the analysis of materials used to build nuclear installations. Conceived more than a decade ago by now-Emeritus professor Rick Holt, the Reactor Materials Testing Laboratory (RMTL) officially opened in September 2015. The one-storey building is about the size of a commercial auto shop and is located in an industrial park several kilometres north of the main university campus. At its heart is a powerful linear accelerator, capable of delivering a beam of high energy protons.

When that beam is directed at a small sample of material, the result effectively simulates what would happen to that same material within a nuclear reactor core. However, any residual radiation is at a low level, and will last only a matter of hours, which means researchers at the RMTL can go about their business without the need for cumbersome infrastructure like remotely operated “hot cells” that would be necessary to shield them if they were taking highly radioactive samples of material directly out of a reactor.

More importantly, investigators working with samples taken from a reactor would be further constrained by the particular conditions found within that reactor. The RMTL, on the other hand, makes it possible to conduct a much more thorough examination by manipulating the many different factors that could be at play.

“You can control your radiation very carefully,” says Daymond. “You can pick the energy of your particles and the number of particles — you can dial your flux. You can control your environment very easily, including stress, temperature, or corrosion. And yet the overall level of radiation exposure to people can be much lower.”

Only a handful of facilities like the RMTL exist anywhere in the world, and the development of this one has taken advantage of the expertise that went into others. Moreover, the site includes a pair of powerful electron microscopes and other material assessment equipment, so that irradiated samples can be immediately studied in detail.

According to Daymond, some of the most pressing queries that the facility can address will surround the fate of zirconium alloys. These sturdy metals don’t absorb neutrons, which has made them the workhorse material for the pipes and tubes that carry water and contain nuclear fuel within reactor cores. The management of these cores — the vital task of ensuring that they continue to operate safely and efficiently — is based on existing estimates of how zirconium copes with this radioactive environment. The RMTL promises to revise those estimates, making them much more accurate and optimizing the safety and efficiency of these expensive installations.

In this respect, the mandate is simple. “Irradiating material is just the first step,” concludes Daymond. “You then have to ask, what did the irradiation do?”