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January 24, 2021

Hopkins alum discusses the history and future of nuclear waste

By YANNI GU | November 3, 2019

Christophor Neuzil, a Hopkins alum and retired research hydrologist with the U.S. Geological Survey, presented on the legacy of nuclear waste on Tuesday as part of the Department of Environmental Health and Engineering’s M. Gordon Wolman Seminar Series.

There are around 450 nuclear reactor units worldwide in over 30 countries, and China alone is planning on building 60 to 80 new units in the next decade. This reality makes nuclear waste disposal a serious issue worldwide.

Nuclear waste is notoriously toxic for extremely long periods of time after its creation, making safe disposal of it very difficult. Experts say time is running out on finding a permanent solution for storing nuclear waste, which must last for at least the next 100,000 years. 

Right now, governments around the world are managing their nuclear waste in intermediate storage, which consists of massive steel tanks which help cool the nuclear waste and protect it from possible damage. However, Neuzil explained that this is not a reliable solution for the future. 

“For nuclear waste, the timeframes that are talked about are on the order of hundreds of thousands of years. It’s unbelievably long,” Neuzil said. “We could add another zero, take away another zero. It’s still a problem in predictability about the fate of it.”

One storage solution scientists have proposed are deep geological repositories. As a leading researcher associated with this option, Neuzil has worked on proposed project sites in Finland, Switzerland and Canada.

The theory is that by storing nuclear waste deep underground, natural geological features can be used to provide a safe and secure insulator for the decaying nuclear waste. However, the actual engineering of the repositories can be extremely tricky.

One challenge is the permeability of the rock surrounding the nuclear waste. The permeability has to be low to protect against the possibility that nuclear material could diffuse out of the repisitoryThat poses a problem as research geologists drill into the ground. 

Neuzil explained how the low permeability causes difficulties in seeing and detecting what is in the rock composition.

“The problem is what you’re not seeing may be a fault, or fracture, or something that you didn’t hit but might be smacked in the middle of your repository,” Neuzil said.

Another example of the complicated situation with the repository site is the dramatic changes in underground fluid pressures. Neuzil emphasized that this is due to glaciation on top of the crust of the earth.

“The deformation [of the crust] is changing the shape and the volume of the pores and is affecting the fluid pressures,” Neuzil said. 

Ice sitting on top of the crust of the earth applies pressure to the rocks and thus squeezes water from their pores. When ice is taken away, the opposite happens. Pores get bigger and start sucking water back in.

Fortunately, the dramatic changes in the underground fluid pressures can be predicted through the glaciation events that happened in the past. The predicted pressure changes are essentially a test for the rock composition’s permeability.

Although they are faced with many difficulties, scientists still ensure the safety of the nuclear waste repository. Finland is on its way to becoming the first ever deep geological repository site officially in use in the world; it is set to open in the mid 2020s. After that, Sweden will most likely be the second. 

When asked about how the European countries are leading ahead with the repository when other countries still have problems with its potential risks, Neuzil explained that the Fins and the Swedes have done a wonderful job at educating their respective publics about what they’re doing.

“The Finish and Swedish populations are much more trusting of the engineering and scientific enterprise than other places,” Neuzil said.

In an interview with The News-Letter, Neuzil explained the difference between the public’s attitude towards the nuclear waste repository in Europe and in the US. 

“We’re doing nothing [to educate the public about nuclear waste repository] in this country right now. There were some efforts during the Yucca mountain, but it was not very successful,” Neuzil said.

Professor Harihar Rajaram in the Department of Environmental Health and Engineering at Hopkins provided more insight on the differences between the implementation of nuclear power in Europe and the U.S. in an interview with The News-Letter after the seminar. 

“In Europe, there is more of an acceptance for science and engineering to solve this problem. They appreciate the importance of nuclear waste and nuclear energy,” Rajaram said. 

“A lot of those countries do not have other energy sources. Nuclear energy is not green-house-gas generating.”

Nuclear energy may have potential as a new energy source to replace the environmentally damaging unrenewable energy sources, as long as it is dealt with properly and safely.

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