Just days before he left office in September 2019, the then Japanese Minister of the Environment Harada told reporters that Tokyo Electric Power Company (TEPCO) would have to dump radioactive water from its crippled Fukushima nuclear power plants into the Pacific Ocean. This of course led to an uproar in media, among NGO:s and local fishermen and neighbouring countries.
The Japanese government quickly pointed out that Minister Harada’s opinion was his alone and that no policy decision had been taken. And that TEPCO would abide by the government’s decision.
When I, guest blogger Sven Östberg, heard the news, I too was taken aback. Could this really be true? In order to get to the bottom of this mystery I and my colleagues asked the Swedish Radiation Security Authority to help us better understand the issue.
It turns out that Japan’s plans to release radioactive water, mainly contaminated with tritium, from Fukushima into the ocean meets global standards of practice in the nuclear industry. This has also been confirmed by IAEA’s Director General Grossi when he visited Fukushima in February 2020.
So, what’s the fuss about then? Not surprisingly, it’s about perception more than the science. Scientists therefore have a great responsibility to explain clearly the radiation and chemistry of tritium. They need to tell the politicians, the media, general public and civil society that not all radioactive nuclei are as dangerous as others.
The following is what I learnt from talking to experts at the Radiation Security Authority. They have visited the Fukushima plants several times and are in close contact with the Japanese authorities and experts.
The damaged reactors still contain fuel, and fuel debris is also present in the buildings. These needs to be cooled by water which then becomes contaminated. Furthermore, the level of groundwater outside the buildings is controlled to be higher than that of the contaminated water inside the buildings to prevent the water escaping outside. This means that groundwater keeps flowing into the buildings and gets contaminated. The amount of water that needs to be purified and stored at the facility thus increases continuously. An additional measure to avoid leakage of radioactive material from the plant, the surrounding soil is kept frozen.
The coolant water is purified with different techniques and the concentration of the main radionuclides, apart from tritium, are reduced to marginal levels. The daily increase in purified coolant that needs to be stored at the Fukushima facility is approximately 135-165 tons. Full storage capacity at the site of the plant is estimated to be reached in summer 2022.
Separation techniques are not practically applicable to the low concentrations of tritium in the water stored at Fukushima. The question of how to deal with the treated water containing tritium needs to be addressed, and different alternatives have been investigated. Two alternatives are possible in practice: vapour release or release to the ocean. The latter alternative is the favoured one since it is easier to monitor and control comparing to vapour release.
What about tritium then? Well, I have learnt that tritium is produced from cosmic radiation in the upper layers of the atmosphere, and that it also exists naturally in very low concentrations in water on earth. It is also be produced as a by-product in a nuclear reactor. Tritium emits a low-energy beta particle when decaying and has a relatively short half-life of around 12 years. The beta particle can only travel a short distance in air, extremely short in water, and does not penetrate the outer layer of the human skin. In order to effect humans, it must enter the body via inhalation or ingestion. Inside the body, the biological half-life is only around 10 days.
The total amount of tritium in storage at the Fukushima plants is approximately 860 TBq. As a layman, I wondered if that was a big number or not.
Let’s make some comparisons. The reprocessing plants in La Hague (France) and Sellafield (UK) releases more than 860 TBq to the sea every year. Nuclear power plants in general release tritium to the sea, and the Swedish plants release around 40 TBq/year. Compared to the amounts released in Europe, the stored water in Fukushima becomes a bit less scary, at least to me. Besides, the Japanese plans are not to release all the water at once but over a phased period of several years and under a controlled and monitored program. According to Japanese calculations, a release of all the tritium stored at Fukushima would lead to an additional dose of less than 0.001 mSv/y to the public. This is less than one thousandth of the dose limit for the public in both Sweden and Japan, and it corresponds to the dose we get from cosmic radiation during 12 minutes in an airplane at marching altitude. I also learnt that the total amount of tritium in the vast amount of stored water is less than 2.5 grams.
Discharge of the tritium contaminated water seems thus in a scientific sense to be quite unproblematic, with very low impact for fishery products. However, perception-wise it will surely have negative PR-consequences for the Japanese fishermen when they try to sell their catch to consumers even though it will be tested as safe. There will most probably be negative reactions from neighbouring countries as well.
My personal conclusion is that the Japanese nuclear security environment before the earthquake, tsunami and Fukushima plants accident of 11 March 2011 had several challenges, for instance generators in the basement, nuclear supervision agency not at arms-length from the energy bureaucracy, no existing emergency plan etc, but that Japan once again showed that the country is good at crisis management and did successfully evacuate the at risk population. The security environment also seems to have improved drastically. The decommissioning of the Fukushima plants is being handled well and a lot of resources are being allocated. Technical problems remain but are most likely possible to be solved with time and resources. However, the issue of storage of radioactive waste is still unsolved, but in this Japan is not alone.
Guest blogger: Sven Östberg, Counsellor (Politics), Embassy of Sweden, Japan