The Fukushima Daiichi nuclear disaster was among the worst nuclear accidents in history. It was caused by the 2011 Tōhoku earthquake and tsunami, when damage to the reactors released a significant amount of radiation into the ocean and, almost 10 years on, claimed the life of a worker.

Over the last decade, the plant has been undergoing a complete decommission to stop further leaks and bring the area back to safe levels. A crucial factor to the decommission is the removal of contaminated water and what to do with it. Currently, there are over 1 million tonnes of water, enough to fill over 400 Olympic swimming pools. Since space on the site to keep all the water will run out in 2022, the Japanese government needs to make a decision about what to do with it.

Contaminated water is treated to remove the vast majority of radioactive elements, leaving behind tritium, one of the two radioactive versions of hydrogen. Tritium is naturally occurring in the atmosphere and it is a byproduct of nuclear reactions. Before nuclear wastewater can be dealt with, it has to be diluted to a level that is safe.

So far, 28 percent of the water has been purified and is waiting to be dealt with. The Japanese government have proposed two options they deem promising: release the water into the ocean or make it evaporate. Both options carry minimal radiation risk to the nearby population. The first would carry an increase of 0.8 microsieverts, the second one 1.2 microsieverts. The average Japanese person receives 2100 microsieverts per year from natural radiation.

The value for releasing the water into the ocean is equivalent to eight bananas, as bananas are slightly radioactive. Not only that but the 0.8 microsieverts value is for releasing the whole water reservoir in one year, while the proposed plan would take several years. A report by the International Atomic Energy Agency agreed that the assessment of the tritium is sound. 

Tritium is certainly radioactive and dangerous in large doses, but it is not harmful in small doses. You could stand next to tritium-contaminated water without risk as the radioactivity produced doesn’t penetrate the skin. It is riskier if ingested, but it has a short biological half-life (less than 10 days), so the long-term accumulation of tritium is improbable both for humans and other animals. That said, if large amounts were released altogether, the effects would be cumulative. 

Tritium has been the main worry, but researchers raised the possibility a few months ago that minute quantities of radioactive elements remain in the tanks, and that if released they might have unknown effects on the marine environment. The team did not argue against an ocean release, but they stated that it would need detailed monitoring to guarantee the safety of the environment and the people who rely on it for their livelihood.  

A decision has not yet been finalized but BBC News reports that Japan's Industry Minister Hiroshi Kajiyama has said that one will be made soon. Opposition to the potential decision comes from environmental groups who don’t want the water released into the ocean as well as local fishing groups that say consumers will refuse to buy products from the area if that comes to pass.

[H/T: BBC News]