Young physicist is looking 100,000 years ahead
Physicist Joni Tanttu, 31, picks up a pinch of his research target from a big plastic sack. The fine-grained powder is bentonite, which will be used for the topmost protective cover around the containers filled with nuclear waste as they are buried in the next few years below several hundred meters of bedrock.
Bentonite easily absorbs water and swells up to many times its original volume. And that is the very reason why sacks of this substance have been brought for material physicists’ examination at the JYU Department of Physics.
In his research, Tanttu uses X-ray tomography, by means of which he investigates how exactly bentonite gets wet and how its water concentration changes in different conditions.
How well does bentonite mass protect a container of nuclear waste in the bedrock chamber and prevent radioactive material from spreading to the environment?
Bentonite found in nature is volcanic clay, but it can also be produced and modified industrially as needed. The quality of bentonite clay varies a lot depending on the way of production.
People engaged in radiation safety research must be able to focus on relevant things, the researcher emphasises.
“There is a myriad of samples and targets to be measured,” Tanttu says. “When we are studying safety extending to hundred thousand years into the future, we must be able to identify the issues that are worth investigating.”
Describing the whole process is a strength in research
When bentonite gets wet, it also swells and penetrates into any cracks and fissures in rock. This is one of the research targets in Tanttu’s upcoming doctoral dissertation. X-rays can be used for exploring the bedrock structure. Geological formations, such as cracks and fissure networks, influence the movement of water in bedrock and also how water can come into contact with nuclear waste.
In X-ray tomography devices, the X-rays construct three-dimensional structural images of the study objects, displaying how different substances move in the material or how the material reacts to changes in temperature or moisture.
In the laboratory, you can examine equally well a nano-scaled paper fibre, a microscopic sample of magnesium composite, or a 30 cm piece of rock. There’s even a whole oven used for melting metals.
The smaller the sample is, the more detailed picture of the object we get.
Tanttu states that a strength of material physics research at the Ģֱ is the comprehensive investigation of processes.
“When studying bentonite clay, for example,” he explains, “our strength lies in understanding and describing the whole wetting process. We can show exactly how the wetting happens.”
Tanttu is a member of a research team specialised in challenging, complex heterogeneous materials. At the JYU Department of Physics, the team is led by Senior Researcher Arttu Miettinen.
The researcher enjoys corporate cooperation
Alongside with basic research, the research team for complex materials pursues research in collaboration with corporations.
Many companies need research knowledge in order to develop their products. Tanttu lists research objects that can be addressed by means of X-ray tomography:
“We can investigate, for instance, the optimal composition for biodegradable plastic, the porosity of concrete, how hydrogen makes metals brittler, or structural changes taking place in recycled metal when a metal mix is melted in the oven. By means of X-rays, we can also find out challenging structures containing water and wood.”
In the cooperation between research and corporations, you often get a chance to consider an issue from many perspectives. A company may have some material they want to investigate, but the exact need for research gets defined only along with joint discussions, Tanttu explains.
Structural information and structural modification may have significant effects on a company’s business.
A holistic approach to research suits Tanttu well in general.
“As a researcher,” Tanttu says, “I like being involved in everything, that is, in research, teaching and social influence.”
In multidimensional work, one continuously gets new, potentially exciting ideas that could be studied, Tanttu says.
“Along with my doctoral research, I have thought, for example, how the heat from nuclear waste could be utilised. In that way, it would not be merely waste. I also hope that we will discover a way to reuse nuclear waste so that as a result there would be no waste at all.”
Particularly the social significance of the topic drew Joni Tanttu to investigate nuclear waste.
“It is also important to keep up bentonite-related research all the time so that the material and safety issues are not forgotten,” he says.
International conference increased desire to disseminate research knowledge
Joni Tanttu comes originally from Heinola. He got interested in physics because of its experimental nature.
“Every measurement or test means listening to the natural world, and through this we seek to build better understanding about it.”
He started his studies in physics at the Ģֱ in 2012 and began working on his doctoral dissertation in 2020, which should be forthcoming in this year.
His research career most recently took him to Singapore in January.
He had succeeded in describing his research project so well that Technology Academy Finland chose him for the group of ten young Finnish researchers who participated in Singapore.
The event was attended by distinguished, internationally renowned researchers, even Nobel winners, who shared their research and advice.
The trip provided numerous new contacts as well as also experiences of success.
“For example, I was praised for the visual design of my poster. For once, I let the images of my research samples speak instead of text, and it was a good move.”
The conference trip also reinforced the notion that it is important to communicate about one’s research to the public in a comprehensible way.
“We are accountable to taxpayers,” Tanttu says.
Tanttu sees around him plenty of demand for expert knowledge.
“Look at the fluctuation of prices in the energy market, for instance. That’s a recent example of where expert knowledge is vastly needed.”
