The Fukushima Daiichi Accident: Water Contamination in Japan

Pat Yontrarak
March 27, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1: Fukushima Daiichi Nuclear Power Plant reactors after the disaster. (Source: Wikimedia Commons)

On April 11, 2011 a huge earthquake, which measured an 8.9 magnitude and was formed on the seafloor east of Tohoku, occurred offshore of Japan. Just over half and hour after this, successive tsunami waves started to strike Japans eastern coastlines: these waves reached up to 13 meters in height and flooded over the embankments designed to protect the Fukushima Daiichi Nuclear Power Plant. [1] Following this, the cooling system and power supply of three reactors in the power plant were disabled by the impact caused by huge waves. This incident resulted in an extensive meltdown of the three cores within the time frame of just a week, causing it to be rated as 7 on the International Nuclear Events Scale (INES) from the high radioactive discharge that was emitted - a photo of what the incident looked like is shown in Fig. 1. This catastrophic chain of events caused hundreds of thousands of people to be evacuated from their homes, cost the Japanese government $360 billion, and around 20,000 direct deaths. [2] Immediately after the incident, authorities were faced with the challenge of cooling the rest of the reactors as well as preventing more radioactive materials from being released into the atmosphere and waterways. Thus, the Japanese government at the time had to take stringent measures and precautions to minimize the environmental impacts of the nuclear meltdown, especially regarding water contamination.

Water Contamination

The fact that the Fukushima Daiichi Nuclear Power Plant accident was rated 7, which was the highest level on the INES, meant that the amount radioactive materials in the water surrounding the site was extremely large. According to researchers, the level of radionuclide activities in the surface ocean reached its highest in early April following the incident and continued to dilute after that. [3] However, it must be noted that there was insufficient field data to fully conclude and accurately deduce the extent of the contamination, the array of radioactive isotopes released, and radioactive uptake into food chains.

Immediately after the incident, the Ministry of Health, Labor, and Welfare (MHLW) issued a statement to water suppliers and government authorities that tap water should not be drunk if any level of contaminants was above the Provisional Regulation Values, leading to the sampling of water sources was conducted for monitoring surveys. The results from these surveys unsurprisingly suggested that levels of radioactive materials, such as radioiodine, radiocesium, uranium, and plutonium, were dangerously high above the PRV so on March 2011, the government ordered consumption and distribution restrictions on tap water. [4] Conducting these surveys came with challenges for some water suppliers because radionuclide detectors were limited. Three months after the incident, orders to conduct frequent surveys were revised to consider the fact that the amount of radionuclide releases from the plant had decreased and contamination levels had been significantly reduced. At this point, water was to be sampled directly from filtration plants rather than from taps so that the water quality could be managed more effectively at its source.

By 2016, the amount of contaminated water leakage from the Fukushima plant meltdown had exceeded 760,000 tonnes, which posed as a crucial drawback to overcome in the decommissioning of the plant. It has been estimated by Tokyo Electric Power Co (Tepco) that collecting and treating all contaminated water surrounding the reactors would be done by the year 2020 - at the soonest. [5] Massive projects to reduce radiation levels have been undertaken with the combined efforts of the public and private sectors. This being said, data projections suggest that 32 billion yen would be required to build an underground wall of frozen earth around reactors that were damaged in order to contain and control the flow of groundwater, with an additional 15 billion yen to be invested in improving domestic water treatment systems. [6] Thus, the long-term impacts of this unfortunate accident yield massive financial burdens to Japans economy along with other serious environmental concerns.


The chain of unfortunate events that followed the huge earthquake lead to an array of immediate as well as long-term impacts, not only on Japan, but also to the rest of the world due to the geographical and economic interconnectivity between different countries. In particular, contamination of water to such dangerous intensities required more stringent regulations and stronger policies to be enacted to ensure the safety and well being of the general public. On the positive side, levels of radioactive materials in water sources have been trending down over time, and effective water filtration systems have made water safe to consume. This major event serves as an important point for the Japanese government to be more assiduous in its objectives and reconsider any future plans of constructing more nuclear power plants along the coastline.

© Pat Yontrarak. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] E. Chang, "The Road to Recovery: Japan after Fukushima," Physics 241, Stanford University, Winter 2016.

[2] F. N. von Hippel, "The Radiological and Psychological Consequences of the Fukushima Daiichi Accident," Bull. Atom. Sci. 67, 27 (2011).

[3] K. Buesseler, M. Aoyama, and M. Fukasawa, "Impacts of the Fukushima Nuclear Power Plants on Marine Radioactivity," Environ. Sci. Technol. 45, 9931 (2011).

[4] N.Hamada, H. Ogino, and Y. Fujimichi, "Safety Regulations of Food and Water Implemented in the First Year Following the Fukushima Nuclear Accident," J. Radiat. Res. 55, 641 (2012).

[5] D. Demetriou, "Fukushima Nuclear Plant Will Leak Radioactive Water for Four More Years," The Telegraph, 10 Mar 16.

[6] K. Takenaka and M. Saito, "Japan to Spend Almost $500 Million on Water Crisis at Fukushima Nuclear Plant," Reuters, 2 Sep 13.