It started with a major earthquake just before three o'clock in the afternoon of 11 March 2011. The Fukushima nuclear power plant coped with the earthquake relatively well. But the reactors could not withstand the tsunami wave 45 minutes later. Once the power supply cut out and the backup system and the majority of the battery-powered systems were knocked out, the essential cooling of the reactor cores stopped working.
When conditions allowed the breakdown to be summarised, it emerged that there had been core meltdowns and explosions of hydrogen gas in three of the six reactors. A fourth reactor, which was empty of fuel, was damaged in one of the hydrogen gas explosions.
The damage to the reactors' cores and containments led to the dispersal of large quantities of radioactive substances in the atmosphere and in the Pacific Ocean.
Following the breakdown, 100,000 people had to leave their homes in a 30 kilometre radius of the plant. Many of them have still not been able, or willing, to return to their houses.
Mattias Lantz is a researcher in experimental nuclear physics at Uppsala University and convener of Analysgruppen in Sweden, the team of analysts which is working to compile and analyse facts surrounding issues that are arising in the public debate linked to reactor safety, radiation protection, radiobiology and risk research. Analysgruppen is linked to Swedenergy and funded by the nuclear power industry.
The year before the natural disaster and the breakdown at Fukushima, Mattias Lantz had returned to Sweden after a year and a half working on a research fellowship in Japan.
He returned to Japan in autumn 2015.
“It is now possible to enter some parts of the evacuated area and remain there during daytime. The village of Naraha, 15 kilometres south of Fukushima, has opened again and around 700 of the 7,000 inhabitants have moved back.“
The accident has hit agriculture hard in the area, which was regarded as Japan's granary.
The authorities have taken measures such as washing buildings and scraping away the top layer of earth in order to decontaminate large areas around the nuclear power plant.
In many places, the material is being stored in large black refuse sacks.
Mattias Lantz also travelled to Fukushima Daiichi where 5,000 employees are working to clear up and decontaminate the area.
“It is a very long-term task. The owner, Tepco, and the authorities are anticipating that the work will take 30-40 years.“
“First the doses in the area had to be reduced so that it was possible to work there. The damaged reactors are located in a cavern that was dynamited in the rock about three metres above sea level. Concrete was laid over the ground to reduce the radiation. A couple of the other reactors have been covered with a tent-like building in order to avoid dispersal of radioactivity during the clearance work.”
High radiation level
According to Mattias Lantz, the staff at the nuclear power plant can work in face masks in certain areas. However, the radiation is so high in other places, including in the damaged reactors, that people cannot enter.
In October 2013 the UN's scientific committee on the effects of radiation (UNSCEAR) presented a report evaluating radiation doses and health consequences of the accident in Fukushima.
In the report the committee assessed radiation exposure in different population groups based on measured and estimated values of the spread of radioactivity in the air, fallout on the ground and in the sea, as well as that taken up in food and water.
On page 88 in the report, UNSCEAR wrote that: ”No acute health effects have been observed among workers [at the nuclear power plant] and the general public which can be attributable to exposure to radiation from the accident. The most important health effects that have been observed thus far among the general public and workers are considered to be in terms of mental health and social well-being linked to the enormous impact the earthquake and the tsunami… had.”
The committee's evaluation took place until October 2012 and UNSCEAR writes that ”Significant medical examinations of the general public and workers are underway, and will continue for many years. The committee feels it is appropriate to evaluate the exposure and effects of radiation in due course after the accident at Fukushima.”
Building a wall of ice
One of many problems that Tepco (Tokyo Electric Power Company) has been struggling with since 2011 is that groundwater is leaking into the damaged reactors and conveying radioactivity out into the Pacific Ocean.
“Thus far they have been pumping the water up before it gets into the reactors and storing it in gigantic tanks. But now they are trying to drill pipes down into the rock to cool the water and create a wall of ice to prevent the groundwater reaching the damaged reactors. The question is whether it will work”, says Mattias Lantz.
Safety culture is crucial
The breakdown in Fukushima is the most serious incident since the Chernobyl accident in 1986. The Japanese authorities have estimated the discharge of radioactive substances into the atmosphere from Fukushima Daiichi to be about 15% of the emissions from Tjernobyl, according to the Swedish Radiation Safety Authority.
Fukushima has entailed a number of consequences for the global nuclear power industry. Among other things, the accident has led to several construction projects and orders being put on hold for a period.
In Sweden, the Swedish Radiation Safety Authority decided in December 2014 that Swedish nuclear power plants must have an independent system for cooling of reactor cores by 2020 at the latest.
"A major problem with Fukushima was that the owner had not practiced the right scenarios, and that the authority had not set the right requirements. A further problem is that there is a culture in Japan where people don't propose improvements because it can be perceived as criticism. It is crucial that a dynamic safety culture is developed."
Three former managers at the Tepco power company, which owns Fukushima Daiichi, were recently indicted. They stand accused of not having taken sufficient precautions to secure the nuclear power plant against a tsunami. Among those indicted is the power company's former chairman.
Nuclear power affects people
Five years after the Fukushima accident three reactors in Japan have been re-started. Mattias Lantz estimates that around half of the 50 or so reactors in the country will be re-started.
"Nuclear power affects people and can be perceived as frightening. The event in Fukushima is spectacular and has destroyed the lives of 100,000 people who have had to leave their homes. It was completely unnecessary."
The International Atomic Energy Agency's (IAEA) report into the accident at Fukushima (pdf in English)
The UN's scientific committee on the effects of radiation (UNSCEAR) report on Fukushima (pdf in English)
Article “Japan fills nuclear gap with fossils and solar”