Australasian Science: Australia's authority on science since 1938

After Fukushima

By Stephen Luntz

A close encounter with Japan’s tsunami and nuclear meltdown led Candice Raeburn to develop new ways to tackle radiation.

Candice Raeburn’s undergraduate degree was in Applied Science majoring in biotechnology, but it was her year off that inspired research far beyond the Honours project norm. Having developed a fascination with Japan while attending a conference, Raeburn took a year off before starting Honours to teach English in a town hardly anyone outside Japan could name.

On 11 March 2011 Raeburn felt the distant rumblings of one of the largest earthquakes ever recorded. Coastal portions of her town were devastated by the tsunami that killed more than 15,000 people across Japan, although fortunately she was far enough inland to be safe from the threat. Only later did Raeburn discover that the tsunami had triggered a meltdown in the nearby nuclear power plant, bringing Fukushima unwanted fame.

Raeburn evacuated to Tokyo and says: “Living in Japan after everything happened, I wanted to do more to help than shaking tins”.

Back in Fukushima, large amounts of radioactive iodine and caesium were released into the environment, contaminating soil and water. Iodine-131 has a half-life of 8 days, so most had decayed within weeks, but caesium-137 has a half-life of 30 years and is proving a more abiding problem.

Caesium-137 is a strong emitter of gamma rays. Moreover, Raeburn explains: “The body treats it like potassium, so it is taken in and irradiates us from the inside”. Although caesium levels are highly varied, locations 30 km from the plant have radiation high enough to cause concern. Schools have scraped topsoil into mounds to prevent exposure to their pupils, but debate rages over whether what remains poses a risk to students.

Raeburn came up with the idea of using caesium’s biological similarity to potassium for good. She thought about genetically engineering a microorganism to absorb the radioactive caesium without suffering damage but quickly decided that the release of a genetically engineered organism with a penchant for radioactivity was unnecessary – and could be particularly unpopular in the home of Godzilla.

Returning to Melbourne, Raeburn set about finding existing bacteria that selectively absorb caesium and can survive high doses of radioactivity. She has tested soil bacteria from several countries, including some native to Japan, and receives regular updates on soil radioactivity around the reactors to determine how large a dose the bacteria have to be able to survive.

One proposed method for removal is to encase the bacteria in a “tea bag-like” membrane and place it in a mixture of contaminated soil and water. If successful, caesium ions entering the bag would be absorbed by the bacteria, eventually leaving the solution outside the membrane safe for use.

“It’s a two-part project,” Raeburn says. “The first is to find a suitable species to assist in bioremediation. The next will be to manufacture a solution to remove contamination from the environment, whether that be a portable bioreactor or some other kind of containment mechanism.”

She says: “I got lucky in finding good species that live naturally in the soil. One of these has been extensively studied for bioremediation, but not in relation to radiation.”

For large-scale application, whatever is developed will need to be able to work in situ. Raeburn has also contemplated soil being scraped into plastic tarpaulins with water and ping-pong-like balls containing the chosen bacteria added. These would allow the isotopes in but would not allow the bacteria to escape. Once the caesium became sufficiently concentrated inside the balls they could be removed for safe disposal.

Raeburn’s Honours project is nearing completion. Rather than taking the research further in a doctorate she has a one-way ticket to Paris, with a job as a researcher in Germany to follow. “The details are yet to be ironed out,” she says. While keen to do a PhD, Raeburn is still considering her focus. Meanwhile she has ideas for several projects she cannot yet reveal.

Raeburn volunteers at Scienceworks in Melbourne, part of which involves assisting during events where adults discover their inner child’s enthusiasm for the science exhibits on display. She also helped organise an event for 15 students visiting from Miyagi University to share their experiences of the 2011 disasters and discuss how it would affect their areas of study.

“I always liked science,” Raeburn says, “but I fell in love with it when we studied genetics in school. We traced diseases like haemophilia through the European royal families. I found the idea that you could carry this disease without knowing you had it enchanting and endlessly fascinating.”