Hiroaki Koide, nuclear scientist and former assistant professor of Kyoto University Research Reactor Institute for 41 years, explains the problems with managing Fukushima Daiichi and the release of radioactive materials like cesium-137 into the environment.
I paraphrased Koide’s speech below:
Fukushima Daiichi’s Units 1, 2 and 3 were in operation during March 2011. Unit 4 was not operating on March 11, 2011, and therefore, did not have fuel in it. However, Unit 4 also experienced a hydrogen explosion and its core was severely damaged. All of its fuel was in the spent fuel pool on the fourth floor. The spent fuel pool, which was exposed to air, contained enough cesium-137 that is equivalent to 14,000 Hiroshima atomic bombs. At the time of the accident, there were serious concerns that if the cooling water in the spent fuel pool dried up, the fuel rods would melt, releasing an extreme amount of radiation release to warrant the evacuation of Tokyo.
Despite that the Japanese government and Tepco clearly knew of this danger, Tepco did not remove the spent fuel rods from Unit 4 until November 2013, a year-long task that was completed in December 2014.
No one knows where the melted fuel and cores of Unit 1 and 3 are. Radiation levels in those units are so high that a person would die in seconds if exposed. Tepco tried viewing the areas with robots, but all of them broke from the radiation.
The only way to control the situation as it is is to pump water into the plant, unavoidably creating massive amounts of radioactive water that is being produced at a rate of 300-400 tons daily. Workers are doing this extremely dangerous work day and night. Not Tepco workers, and not even subcontracted workers, but sub-sub-sub-sub-sub-sub-sub-sub contracted workers, eight or nine levels deep at the very bottom of the wrung. “So many commissions are taken from their salaries at they are not even receiving minimum wage.”
An even more grave issue is that the cores of Units 1, 2 and 3 are melted. “How do we deal with that?” Tepco plans on “plucking out” the “lumps” of melted fuel by reaching into the pressure vessel down into the containment vessel and extracting the fuel from the top. However, if they were to open up the pressure vessel to get in, a huge amount of radiation would be released into the air. To deal with this, Tepco plans on repairing the sides of the pressure vessel and flooding it with water and then plucking out the fuel, which they believe sits together in the lump, like a “dumpling.”
Professor Koide’s response to this plan is:
1) We don’t have the technology to determine where the holes in the containment vessel are, let alone the means to repair it.
2) It is impossible that the melted fuel exists in a dumpling-shaped lump. It could have spread horizontally and even gone through the floor of the containment vessel.
3) If Tepco and the Japanese government try to extract the fuel from above, it will only be possible to remove some of the fuel, not all of it. Koide recommends dealing with this situation in the same manner as the Chernobyl plant by burying the plant in a concrete sarcophagus. However, we cannot start thinking about building a sarcophagus until the spent fuel rods are removed from the spent fuel pools at Units 1, 2 and 3.
How long will it take to remove the spent fuel rods at Units 1, 2, and 3? “I cannot even make a prediction. I probably won’t be alive when it occurs.” Even at Chernobyl, the concrete sarcophagus is aging and is being replaced. That was only one reactor. Fukushima Daiichi has three melted reactors. We must plan on burying the reactors in concrete and maintaining the sarcophagus with a centuries-long timeline.
The Japanese government gave a report to the IAEA with information of the cesium-137 released into the atmosphere. [Koide shows a diagram of Japan with color-coded grades of contaminated areas.] Unit 1 alone released six to seven times the cesium-137 that was released from the Hiroshima bomb. Unit 2 released the greatest amount. All together, Units 1, 2 and 3 released 168 times the amount of cesium-137 from the Hiroshima bomb. This is only the cesium-137 released into the air. Every day, more contaminated water is being produced and released into the sea. The total amount of cesium-137 released into the environment from Fukushima Daiichi is equal to several hundred times that of the Hiroshima bomb. The radioactive materials that were released into the atmosphere were carried by the “previaling westerly” winds not only all over the Kanto great plain of Japan, but also across the Pacific Ocean and contaminated the western coast of North America.
As a result of the contaminated areas in Japan, over 100,000 people are not able to return to their homes. The most highly contaminated areas (shown in red on the diagram) are designated as “radiation controlled areas.” Until now, there were very strict regulations for these areas. For example, a person could not legally remove anything from a radiation controlled area that emits more than 40,000 becquerels of radiation per square meter. However, the areas in blue have areas over 60,00 becquerals per square meter. Dark green areas have 30,000-60,000 becquerels per square meter. If one abides strictly by the law that says that nothing over 40,000 becquerels per square matter can be removed from a radiation controlled area, then Japan must designate 14,000 square kilometers of Japan to be radiation controlled areas. However, because this is an emergency situation, the Japanese government says that normal laws do not need to be followed. Instead, they have abandoned people to live in these highly contaminated areas.
Overall, 15,000 terabecquerels of cesium-137 were released into the atmosphere, 2400 terabecquerels of which fell on the Kanto region. In weight, the total radioactive cesium-137 would equal 4.7 kilograms, and 750 grams on the Kanto region. You cannot sense the radioactive materials. To reduce radiation exposure to Kanto citizens, people have tried removing contaminated topsoil, equal to tens of millions of bags of soil. This is only a temporary solution. The contaminated soil contained seeds that grew and broke through the bags.