A new study estimates that the cleanup of Fukushima’s 2011 nuclear disaster will cost hundreds and billions of dollars. However, the environmental impact could be even greater, as nearby lakes have been contaminated for decades.

A group of researchers led at the University of Tsukuba found that Lake Onuma on Mount Akagi could have been contaminated by radioactive cesium137 (137CS) for around 30 years after the catastrophe.  

Researchers used fractional diffusional methods to determine that radioactivity concentrations will occur for up to 10,000 days after an accident. 

After the nuclear accident, radioactivity concentrations dropped sharply. But, they slow down over the months and the years that follow.

Lake Onuma, a closed lake, has very little inflow and runoff water. 

Japan's Lake Onuma could be contaminated with radioactive cesium-137 (137CS) for roughly 30 years after the Fukushima disaster, a new study has found

A new study has revealed that Japan’s Lake Onuma could potentially be contaminated with radioactive Cesium-137 (137CS), for around 30 years after the Fukushima nuclear disaster.

The catastrophic Fukushima nuclear disaster in 2011 caused an estimated 250,000 people to evacuate their homes

Fukushima nuclear catastrophe in 2011 caused approximately 250,000 people evacuate their homes. 

Lake Onuma is a closed lake and has a limited amount of inflow and runoff water

Lake Onuma is a lake that is closed and receives very little runoff and inflow water.

Professor Yuko Hatano, one of the study’s coauthors, stated in a statement that previous investigations had used the two-component decay functions model, which is the summation of two exponential functions to fit the measured radioactivity concentration of 137Cs. 

“Our work is instead based upon the fractional diffusion modeling, a framework that captures complex diffusion phenomena occurring in the lake waters. These processes include convection, turbulent mixing, and absorption from plankton and other organisms.  

In 2016, the Japanese government increased its official projections for nuclear disaster costs to $188billion.

Other estimates suggest that the final cost could be as high as $1 trillion, and that the recovery could take as long as 40 year. 

According to the Environmental Protection Agency Cesium-137 has a relatively long half-life of approximately 30 years. 

Radiation sickness, death and burns can all result from exposure to radioactive isotopes.

The experts used a model known as fractional diffusion to come up with a longer-term prediction for the 137Cs concentration in both the lake water and pond smelt, a typical fish that lives in the lake

To forecast the 137Cs concentrations of lake water and lake smelt, experts used fractional diffusion. This model is typical for fish that live in the lake.

To predict the 137Cs concentrations in the lake water and pond, experts used fractional diffusion. This model is typical for fish that live in the lake.

The researchers stated that the concentrations of 137CS were measured in the pond smelt and lake water for 5.4 year after the accident.

The study found that the activity concentrations of 137Cs in pond water smelt decreased rapidly between August 2011 (160 days following March 15, 2011), and September 2012 (552 day), but showed an increasing trend after October 2012 (592 day), they wrote.

“This trend is consistent to the change of the 137Cs Activity concentration of the lake waters in Lake Onuma.”

According to the formula, experts believe that radioactivity will occur for up to 10,000 day after the accident. 

Given the formula, the experts believe that radioactivity concentration will happen for up to 10,000 days following the accident

The formula suggests that radioactivity concentration could occur for as long as 10,000 days after an accident, according to experts.

In contrast, water in Russia's Svyatoe lake after the Chernobyl accident had 137CS concentration for a period of approximately seven to 13 years, or 2,400 to 4,900 days

The water in Russia’s Svyatoe lakes after the Chernobyl incident had a concentration of 137CS for approximately seven to 13 year, or 2,400-4,900 days.  

The water in Russia’s Svyatoe lakes after the Chernobyl incident had a concentration of 137CS for approximately seven to 13 year, or 2,400-4,900 days. 

The researchers used the fractional diffusional method to come up with their findings

To arrive at their findings, the researchers used fractional diffusional to do so.

Professor Hatano said that both models correspond to the radioactivity concentrations of the lake water, pond smelt, and other measurements made in the first few decades after the accident. 

“Our results however show that radioactivity concentrations decreases if fractional diffusion models are used instead of the two-component decay function model.  

Researchers will be able to better understand radioactive contamination in nearby lakes that are currently closed. Residents will also have a better understanding of the living conditions around the lakes. 

Scientific Reports published the study last month.

A separate group of researchers discovered that the wildlife in the area, including wild boars and rat snakes are thriving and have not experienced any adverse health effects.

This is likely due to the fact that cesium-134, one of the major radioactive materials released during the accident, saw its levels decrease in the area by almost 90 percent, as it has a relatively short half-life of just over 2 years.

In January 2020, a separate study found that more than 20 species, including wild boar, macaques and a raccoon dog were thriving in the ‘exclusion zone’ near the disabled Fukushima Daichii nuclear reactor.

Researchers discovered in July that the disaster had created a boar-pig hybrid. This was because both species mated with each other.

Japan was devastated by Fukushima’s nuclear disaster. Large swathes of Honshu, Japan’s main island, were permanently moved to the east.

It unleashed tsunami waves that were more than 130 feet tall, destroying homes of 450,000 people, and sending several nuclear reactors at Fukushima Nuclear Power Plant into meltdown.

An incessant stream of radioactive, toxic substances was released into the atmosphere, forcing thousands to flee their homes. 

In April, the Japanese government announced it will start releasing treated radioactive water from Fukushima into the Pacific Ocean in two years, a move that has angered China, South Korea, fishermen and residents of the island nation. 


A tsunami measuring 33ft (10m) high that killed almost 19,000 people in Japan crashed into Japan’s Fukushima nuclear plant in 2011. 

This caused numerous meltdowns, allowing radioactive fuel rods to escape and debris to escape from enclosed areas.

Researchers are still trying to salvage fuel from the wasting reactors, even though it is almost a decade since the disaster.

Pictured is an aerial view of the reactors of the tsunami-stricken Fukushima Dai-ichi nuclear power plant stand in Okuma, Fukushima

The aerial view shows the Fukushima-based Fukushima-Dai-ichi nuclear power plants, which are located in Okuma (Fukshima).

It is estimated that only 10% of the nuclear fuel remains after the meltdowns.

The radioactive waste from the plant that was damaged is believed to have leaked into the Pacific Ocean. This could be reaching as far as the West Coast of the United States. 

Researchers are now pinning their hopes on remote-controlled swimming robots to locate the lost fuel in order to work out the safest way to remove it. 

The government has lifted evacuation instructions for most of the affected areas, except for certain no-go zones that are high in radiation.

Authorities are encouraging evacuationes to return but the Fukushima Prefecture population has more than halved since the two million that lived in the predisaster period.