Going nuclear about Fukushima's waste
When it comes to radioactive material, can we ever be safe? Science gives a cautious nod, but Japan's detractors don't want a discharge into the Pacific ocean
Late last month, Japan started to release treated radioactive water from the Fukushima nuclear power plant that was wrecked by an earthquake and a tsunami in 2011. The question being asked is: Does the water, which is being discharged into the Pacific Ocean through a pipeline, pose a risk to the marine environment, particularly organisms that may ingest or inhale radioactive materials?
On one side of the debate, environmental groups have protested the discharge, while China has gone to the extent of banning seafood imports from Japan. On the other side, Japanese authorities insist that the concentrations of radioactive substances are well below prescribed limits, while the International Atomic Energy Agency (IAEA) is satisfied that the released water meets regulatory standards. (Read the IAEA report here)
Earlier this week Japan told the World Trade Organization (WTO) that China's ban on Japanese seafood after the release of treated water from the Fukushima nuclear plant was "totally unacceptable", Reuters reported.
Indeed, the radiation dose from the water being released is several times lower than what humans are naturally exposed to. Data in the public domain show that most radioactive substances have been reduced to a trace, while one unremoved element is at a concentration that is well below the benchmark.
That unremoved element, tritium, is at the centre of the debate. Since tritium is difficult to remove, the Japanese authorities have diluted the water that is being discharged. Environmental groups, however, have questioned whether any amount of a radioactive substance can be safe for the environment.
What’s in the water
Since the 2011 disaster, huge amounts of water were used to cool the reactors at the wrecked plant, while contaminated water was pumped out.
Over the years, 1.3 million tonnes have been stored in more than 1,000 tanks on the site. Now, with the tanks running out of space, the Japanese government has allowed the discharge after treating the water with a procedure called Advanced Liquid Processing System (ALPS).
Developed by the Japanese company Toshiba, the system purifies contaminated water that contains radionuclides, or radioactive atoms, through processes that include pumping and filtering the water. A series of chemical reactions removes 62 radionuclides, bringing their quantities to tiny fractions of regulatory standards. Among these are the elements of cobalt‐60 (causes skin burns), caesium‐137 (enters soft tissues and increases cancer risk), and strontium‐90 (potential cancer threat to bone and bone marrow).
Tritium, which is not removed, is an isotope of hydrogen — it has largely the same chemical properties, but its atomic nucleus is slightly different. Compared to the other elements, tritium is a relatively weak source of radiation. However, if consumed in large quantities, it can increase the risk of cancer.
Assessing the risk
Radioactivity is measured in Becquerels (Bq). The Tokyo Electric Power Company, which handles the Fukushima plant, is diluting the water before discharge to a level that brings the tritium concentration down to 1,500 Bq per litre — less than 1% of the regulatory standard of 60,000 Bq/l. In fact, it is less than even the WHO standard of 10,000 Bq/l, and that is for drinking water.
As far as Japan is concerned, the low radiation dose, the dilution of the water, the fact that radiation from tritium is much weaker than that from other pollutants, and that other nuclear plants have released greater amounts of tritium in the past with minimal effect of marine life, are points that they are expected to put forward even during the G20 summit taking place in New Delhi from September 9 onwards.
Environmental scientist Jim Smith of the University of Portsmouth, who has been researching the impact of radioactive pollutants for decades, including pollutants from the Chernobyl and Fukushima disasters, believes that discharged water is the best option.
“Nothing is 100% safe — even respiration can lead to DNA damage through the production of reactive oxygen species in cells. The limits are set to be extremely cautious — the radiation dose is estimated by the IAEA to be below 1 microSievert per year [the unit at which the radiation dose to humans is measured] which is more than 2000 times lower than the natural radiation dose we all get annually,” Smith said.
Japan’s Ministry of Economy, Trade and Industry (METI) has released data on tritium released by nuclear plants around the world. China released about 220 teraBequerels (220 trillion Bequerels) from its Yangjiang plant and 112 TBq from in 2021, while South Korea released 71 TBq and 49 TBq from its nuclear plants in Wolsong and Kori respectively, in the same year. In contrast, France’s La Hague reprocessing plant released 1000 TBq in 2021 and UK’s Heysham 2 plant released 323 TBq in 2021.
METI compares these with the Fukushima plant, which released 2.2 TBq liquid tritium in 2010, when it was active. The plan now is to release 22 TBq every year.
Call for caution
The form in which tritium is released is important. As an isotope of hydrogen, tritium tends to react with the same elements and compounds as hydrogen does. When tritium replaces ordinary hydrogen in a water molecule, the latter becomes tritiated water, and its environmental impact in this form is reduced, Smith wrote in The Conversation recently.
The risk comes when tritium replaces ordinary hydrogen in an organic molecule. This “organically bound tritium” can subsequently be ingested by marine organisms. The Japanese authorities need to ensure that there are not significant amounts of organically bound tritium in the water they release, Smith wrote. In fact, he told HT, that it does not matter if the tritium becomes organically bound after the discharge.
“The important thing is that the tritium is discharged in tritiated water form. It can subsequently become organically bound in organisms but this doesn't mean it biomagnifies. The only problem is if it is discharged in organically bound form, then it can biomagnify as it isn't diluted by the mass of non-radioactive water it is discharged with,” he said.
Biomagnification means the concentration of the radioactive substance in organisms grows higher and higher as it moves up the food chain. While organically bound tritium could biomagnify, the tritium in tritiated water would not. Organisms exposed to tritiated water would have about the same concentration of tritium in their bodies as the surrounding water.
Is China’s ban on seafood from Japan justified?
Some radioactive substances from the wrecked plant have reached marine life, which has been reduced over the years. Various studies, however, have found that the amounts pose very little risk.
“We studied crabs in ponds near Fukushima and found no effect of radioactivity from the 2011 accident on their development,” said Smith, who has researched the Chernobyl accident since 1990, besides Fukushima.
He said lakes around Chernobyl, including the Cooling Pond of the reactor, are at radiation levels thousands of times higher than the Pacific will be following this release. “We have seen some subtle effects of radiation on fish in the most contaminated lakes, but in general the aquatic ecosystem is thriving.”
Among other studies, a paper in the Marine Pollution Bulletin in July this year found that tritium concentrations in seawater in the Fukushima region were around 0.1 Bq/litre.
Jordi Vives I Batlle of the Belgian Nuclear Research Centre, who has conducted a series of studies on radioactivity in the Fukushima region since the disaster, examined the effect of the planned discharge in a paper in the journal Integrated Environmental Assessment and Management last year. While information then was limited, his preliminary screening assessment indicated that the radiological impact on people and the environment is very low.
In 2014, a study in Environmental Science and Technology found that coastal fish in the Fukushima region had increased dose rates of caesium-134 and Cs-137 as a result of the disaster. This too was low: a hypothetical human consumer of 50 kg of fish, gathered 3 km from the plant in 2013, would have received a total effective dose of approximately 0.95 microSieverts per year, of which 0.13 microSieverts per year would be solely from the nuclear plant radionuclides. This is well below the benchmark of 1 microSievert per year.
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