Fukushima nuclear wastewater three questions



Where it came from

In 2011, the earthquake and tsunami affected the Fukushima Daiichi nuclear power plant 1 to 3 reactor core meltdown. Since the accident, the plant's operator, Tokyo Electric Power Company (Tepco), has continued to pump water into the containment vessels of Units 1 through 3 to cool the reactor cores and recover waste water.

As of March this year, combined with the continuous inflow of groundwater and rainwater, the plant had produced 1.25 million tons of nuclear wastewater, and the rate of increase is 140 tons per day. The capacity of its existing tanks is capped at 1.37 million tons, and Tepco says they will be fully filled by the fall of 2022, leaving no more space for a large number of storage tanks. The government and Tepco have argued that there is a need to ensure that the Fukushima Daiichi plant has space to store the large amounts of radioactive material produced during the decommissioning of the reactors.

Tepco also believes that the long-term storage of millions of tons of nuclear wastewater is at risk of leakage. On February 13 this year, a 7.3 magnitude earthquake struck off the coast of Fukushima Prefecture. The quake caused 53 of the thousands of water storage tanks at the Fukushima Daiichi plant to displace by between 3 and 19 centimeters.

As for why they did not add water storage tanks outside the nuclear power plant, the Japanese government and Tepco said that it would take a lot of time to coordinate with local governments and transport nuclear waste water over long distances. Critics say the move is not impossible, but that the Japanese government and TEPCO do not want to do it.

On April 13, a citizen in Tokyo, Japan, uses his mobile phone to read the news that Japan has decided to discharge contaminated water from the Fukushima nuclear power plant into the sea. Photo by Du Xiaoyi/Xinhua News Agency

How to discharge

According to the decision of the Japanese Cabinet meeting on the 13th, when discharging nuclear wastewater, the tritium contained in the water will be diluted to less than one-fortieth of the national standard for tritium discharge of nuclear power plant wastewater in Japan, that is, the tritium activity of 60,000 becquels per liter of water, and the entire discharge is expected to end before the completion of the reactor dismantlement work at the Fukushima nuclear power plant in 2041 to 2051.

The nuclear wastewater of Fukushima Daiichi nuclear power plant contains cesium, strontium, tritium and other radioactive substances. The Japanese government and TEPCO say the filter, called the Multi-nuclide Removal Facility, can remove 62 radioactive substances except tritium, which is difficult to remove from water.

According to the Japanese Ministry of Economy, Trade and Industry data, as of June 2020, the total activity of tritium in the nuclear wastewater of the Fukushima First nuclear power plant is about 860 trillion becquerels, with an average of about 730,000 becquerels per liter of water.

However, the actual effect of the "multi-nuclide removal device" is not as ideal as claimed. As of March 2020, about 70% of the nuclear wastewater treated by such equipment exceeds the discharge standard, of which about 15% exceeds the discharge standard by 10 to 100 times, and 6% exceeds the discharge standard by 100 times. The nuclear waste water needs to be filtered again.

Photo taken on April 13, 2019 shows the Fukushima Daiichi nuclear power plant in Japan.

Hazard geometry

The Asahi Shimbun has reported that many nuclear power plants in Japan and abroad discharge waste water into the sea under the premise of controlling tritium content. In the five years before the Fukushima nuclear accident, the total activity of the average annual discharge of tritium into the ocean by Japan's nuclear power plants was about 380 trillion becquerels. In addition, in the Three Mile Island nuclear accident in the United States, about 24 trillion becquerels of radioactive material were released into the atmosphere over a period of about two years.

The nuclear wastewater produced by the Fukushima Daiichi nuclear power plant is different from the tritium-containing wastewater discharged during the normal operation of the nuclear power plant. Many of the nuclear waste water at the nuclear power plant came into contact with the nuclear fuel that melted down the core, and the composition of radioactive substances contained in the water is extremely complex, and it is doubtful whether radioactive substances other than tritium can be completely removed.

Japan plans to ask the International Atomic Energy Agency for guidance on emissions. In an interview with Japan's Kyodo News agency in December, the agency's director general, Gregory Grossi, said that the IAEA is exploring the issue of nuclear wastewater treatment with Japan, and once Japan makes a decision on the issue and requests the agency to monitor it, the IAEA is willing to send an international monitoring mission.

But the IAEA's involvement has not entirely allayed concerns. The Japanese government and Tepco have made many mistakes in their handling of nuclear accidents in the past, leaving them with little credibility. The Citizens Committee for Nuclear Power, a non-governmental organization composed of Japanese citizens and scholars, issued a statement on the 11th, strongly protesting the Japanese government's plan to discharge nuclear waste water into the sea. The organization believes that the Japanese government has failed to form a social consensus on how to deal with nuclear wastewater based on sufficient discussion, and tritium is tritium's harm to the environment and biology.

The Citizens Committee for Nuclear Power said that the Japanese government and Tepco itself have been responsible for the release of large amounts of radioactive materials into the environment from the Fukushima nuclear power plant, and must not allow additional intentional emissions of radioactive materials on this basis.