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Causes of the Fukushima Nuclear Reactor Meltdown

Paper Type: Free Essay Subject: Environmental Sciences
Wordcount: 3743 words Published: 18th May 2020

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Nuclear energy has always been one of humanity’s pursuit for clean energy, however, proper care needs to be taken for harvesting this resource, as it is extremely dangerous due to its radioactive nature. When handling nuclear energy, negligence of safety measures would have long-lasting consequences for years to come. Large-scale engineering disasters, like the Fukushima Nuclear Reactor Meltdown, serve as reminders and guidelines of how the mistakes made can be avoided and how to improve future designs. This disaster at Fukushima was initiated by the Great East Japan earthquake on March 11, 2011, which had a magnitude of 9.0 Richter. It set off a tsunami that led to damage to the power supply lines, and destroying the back-up generators. The loss of power resulted in a lack of energy for the cooling system of the reactors, ultimately leading to the release of high amounts of heat. Without any heat sinks, the three reactors began to melt and breached the vessels’ floors, partially exposing the nuclear material in the cores. There were social and economic backlashes due to the contamination of nearby waters and public distrust over operators of the power plant. This research paper will focus on finding the main causes of the disaster through investigation and analysis of the events leading to the accident and the aftermath of the accident. Was the power plant adequately prepared for natural disasters? Were there concrete guidelines and policies in the event of a reactor meltdown and were they enforced by official personnel?



The Fukushima Nuclear Reactor Meltdown is an event which is commonly associated with images of exploding reactor buildings, numerous stories of valiant attempts of saving the plant site, poignant accounts of families displaced from their homes and communities that were rendered inhabitable. The meltdown ultimately resulted in damage to the daily lives of residents in Fukushima, Japan and indirectly impacted other sectors and countries.

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The facility where this disaster occurred, is located on Japan’s Pacific coast, in north-eastern Fukushima, about 100km South of Sendai, and is operated by Tokyo Electric and Power Company. It was made up of six boiling water reactors constructed between 1971 and 1979. At the time of the accidents, only reactors 1-3 were operational, and reactor 4 served as temporary storage for spent fuel rods. The Great East Japan earthquake and tsunami, which occurred on March 11, 2011, was the trigger of this horrible nuclear accident. This massive earthquake of magnitude 9.0 Richter resulted in electricity, gas and water supplies, telecommunications, and railway services being severely disrupted and, in many cases, completely shut down. These disruptions greatly affected the Fukushima Daiichi nuclear power plant, causing a loss of all on-site and off-site power.

Seawater pumps, emergency diesel generators, and distribution boards were submerged due to large tsunami waves, and all emergency diesel power generators ceased to work except for one generator in Unit 6.[3] Although these operating reactor units were safely shut down, without the operation of the seawater pumps to cool the reactors;  the reactor cores overheated . During this time, the workers at the plant made several attempts to cool the reactors using truck-mounted water cannons and water dropped from helicopters. Those efforts met with some success, which temporarily slowed the release of radiation. However, the nuclear fuel still melted and the containment vessels were breached, ultimately leading to the release of radioactive materials from the reactors.

In addition to this, explosions resulting from the buildup of pressurized hydrogen gas occurred in the outer containment buildings enclosing reactors 1 and 3 on March 12 and March 14, respectively. A third explosion occurred on March 15 in the building surrounding reactor 2. The explosion punched a second hole in the containment vessel; the first hole had been created earlier by melted nuclear material that passed through the bottom of the vessel. The explosion, along with a fire touched off by rising temperatures in spent fuel rods stored in reactor 4, led to the release of higher levels of radiation from the plant. As a result of the radioactive materials which were released from the nuclear power station, widespread contamination of the environment occurred and there was an immediate evacuation of the surrounding area[1].

To this day, the disaster zone remains a huge building site with the immediate danger cleared but an immensely difficult clean-up job still looming. Large-scale engineering disasters like this, are recorded in the history books. Along with successful ideas and processes, engineers look at these failures to guide their future designs. It is these failures that become more reliable teachers. [2] Nuclear power is a choice of energy which gambles with disaster.[5] If proper care and safety measures are not taken, the effects could be even worse than what occurred at the Fukushima Daiichi Nuclear Power Plant. In this study, the causes and effects of the meltdown will be investigated in great detail so that these mistakes can be noted for future designs and processes. Additionally, it is only after analyzing what went wrong, can recommendations be made to improve future designs.




1)     Irresponsibility of the Government and Company

The government and the company neglected the odds of a disaster like this occurring in Fuskishina because they came to the conclusion of something like this occurring was very slim. The governments and company’s arrogance and irresponsibility lead them to only creating a system that would fulfill their day to day needs instead of focusing on the greater picture.[5] (p.19)

2)     Lack of Preparation

Since the government and company did not take into account the possibility of a disaster like this occurring, they created a system that would cover the bare minimum and satisfy their day to day problems. Due to this lack of preparation when the Fukushima disaster hit they did not have the technology available to fight against the disaster and stop it. [5](p.19)

3)     Profit over safety

The government and company saw it was more profitable to build a system that would consist of a make up of cheaper technology then it would be to invest in technology that would prevent a “very unlikely” disaster from occurring in the first place. [5](p.24)

4)     Underestimation of the situation

Fig. 1. Diagram of Fukushima Daiichi Nuclear Power Plant Depicting The Cliff Elevation, Height of Fukushima Nuclear Plant and the Tsunami.[xx2]

Flooded power room [xx3]

5)     Malfunction of nuclear disaster robots

The Effects

The accident that occurred at the Fukushima Nuclear Power Plant ultimately caused radioactive materials to be released into the environment, making the complex and long-term damage as well as  disorder among persons in society. This section will examine the effects of the disaster.

  1. Evacuation

Radioactive cesium contaminated 11,580 square miles (about 30,000 km2) of the land surface of Japan causing an area of 130 square miles to be designated as unsafe for human habitation. [xx4] A total of 165 000 residents, including 20 000 voluntary evacuees, left their homes by May 2011, two months after the accident. Following this, a total of 98 000 evacuees or relocated persons in MAy 2016. [xx6]


  1. Mental Health and Psychological Distress

 It should be noted that many of the relocated persons were separated from family members and communities. The evacuation also led to small, hastily constructed houses in which persons resided. Because of loss of jobs (such as working in farm fields) as well as avoiding radiation exposure outdoors, many staying inside and avoiding physical labour. There was a report that showed a significant association between the evacuation and lifestyle changes and increased cardiovascular risks in adults, including obesity, hypertension, dyslipidemia and diabetes mellitus. Within 1 year of the disaster, in March 2012, 21.6% of residents from evacuation zones had possible posttraumatic stress disorder, similarly 14,6% had probable depression in 2012. However, over time these level gradually improved.

Figure showing the multidimensional  psychological reactions of the Fukushima accident [xx5]

  1. Contamination of food and water

It was discovered that there were cases of contaminated vegetables, drinking water, dairy products and meat. In March, 2011, tests detected 1,190 becquerels (Bq) of iodine in fresh milk in Fukushima Prefecture and 210 Bq/kg  were detected in tap water in Tokyo.This value exceeds the provisional limit for ingestion by infants of 100 Bq/kg. In April, the iodine levels in young lancetfish off the coast of Ibaraki Prefecture,  were detected to be 4080Bq/kg which exceeded the provisional limits.In February 2012, almost a year later, there were 302 cases in the Fukushima Prefecture of vegetables that exceeded the permissible levels, 203 of marine products, 18 of dairy products, 147 of meat and 2 of grains. These limits were also exceeded in other prefectures such as Tochigi, Gunman and Tokyo. A number of countries also barred imports of Japanese foods or demanding certification of exports. [xx7]

  1. Economic loss

Estimating the cost of the accident is challenging as the accident is not “over” since not all the melted fuel have been located and radioactive material continues to leak into the environment. The Japan Center for Economic Research has calculated that the clean-up from the accident may reach as high as 20 trillion yen. Additionally, the Management and Financial Investigative Committee on TEPCO calculated that the transient damage alone is approximately 2.6 million yen, while the estimated compensation will exceed 1 trillion yen in just the first fiscal year.[xx7]

  1. Loss of trust in the nuclear industry/ Impact on power supply stability

The expansion of the nuclear industry slowed dramatically. All plans to build new nuclear power plants were suspended. As of June 2011, 31 of Japan’s 50 nuclear power plants (excluding Fukushima Daiichi’s Units 1-4) were shut down. At one point in time, for two months, all 50 reactors were shut down in 2012. The need to use thermal fuel arised and in response to this, electricity fees raised from September 2012; [xx7]

The accident has had an impact on all aspects of Japan’s society; including agriculture, forestry, and fisheries, manufacturing, education, industry, tourism, politics and energy policy. Nuclear power may have been just one of the many methods to generate power, but the accident proved to have an enormous impact.

This led to the loss of the cooling function at the three operating reactor units. The objective of “cooling” a reactor is to achieve a state wherein the reactor is stabilized at “cold shutdown” (a condition in which the temperature of the water within the reactor is below 100ºC). The removal of what is known as the “decay heat” that the fuel in the reactor continues to produce is needed for cold shutdown to occur. [xx2]A




In conclusion, incident at Fukushima was caused by the negligence of the operators at the plant. The reactor meltdown could have been prevented if they made proper cooling systems that actually covered the reactors and had backup batteries that lasted more than 6 hours. This would have prevented the backlash that it had on the country. Since it had lost the people’s faith in nuclear energy due to the effects that radiation had on the fishing industry, nearby waters, and birth defects of infants. The government should have reinforced the safety guidelines of that plant and those officials should have prepared for the worst case scenarios. Instead they were overconfident and careless about their work which led to their downfall.



The policies and changes due to the Fukushima Daiichi power plants were drastic due to public distrust of Nuclear energy and the handling of it. It should be noted that after the accident in Japan and certain parts of the world started phasing out nuclear energy in favor of renewable energy or fossil fuel. While anti-nuclear energy movement existed since before the Fukushima Daiichi Nuclear Disaster [x1], It acted as a catalyst that accelerated policies regarding phasing out said energy, most notable being was Germany which has planned to phase out its nuclear power plants by 2022. [x2] and Japan which has started setting down policies that try to decrease the dependency on nuclear energy. Overall in terms of construction of new power plants or the usage of the nuclear energy most countries around the world have either been opposed, closed down their Nuclear power plants or are in the process of phasing them down, However on the other end of the spectrum , some countries like China have begun construction of New reactors in favor of dealing with their Carbon emission problems.

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In terms of design, research has been done on replacing solid fuel in the favor of liquid base fuel since half a century ago. These designs are an improvement that could have stopped the disaster if they were in place advantages for that: firstly, that liquid base fuel would work in atmospheric pressure so chances of explosions would be low and secondly, Because the normal operation of the reactor is in molten state and salts are solid at room temperature if something happens during emergencies to the pipes or other vessels/containers the salt would solidify and harden so it would be considered more safe than a solid based reactor. However it should be noted that Molten Salt Reactors(MSR) pose their own sets of challenges that being that thorium-232 the common fuel used in these reactors will convert into uranium-232 which is as deadly plutonium-239 and the fact that MSR needs to be made out of corrosive reactor material to deal with the corrosion of the molten salt. [x3] Still this disaster has at least acted as a reminder to the alternative of solid based fuel.





[1] S. TANAKA, “Accident at the Fukushima Dai-ichi Nuclear Power Stations of TEPCO -Outline & lessons learned-” Proceedings of the Japan Academy, Series B, vol. 88, no. 9, pp. 471–484, 2012.Available:


[2] H. Petroski, “Learning from bridge failure,” Los Angeles Times, 04-Aug-2007. [Online]. Available: https://www.latimes.com/la-oe-petroski4aug04-story.html.

[3] I. Suzuki and Y. Kaneko, “Brief Overview of the Tohoku 3.11 Mega Earthquake, Tsunami, and Fukushima NPS Disasters,” Japan’s Disaster Governance, vol. 4, pp. 7–23, Dec. 2012.Available:


[4] The Editors of Encyclopaedia Britannica, “Fukushima | prefecture, Japan,” Encyclopædia Britannica. 08-Mar-2012.Available:


[5] D. Lochbaum, E. Lyman, S. Q. Stranahan, and The Union of Concerned Scientists, Fukushima : The Story of a Nuclear Disaster. New York: The New Press, 2014, p. 8.Available:


[x1] S. L. Rothwell, “Antinuclear movement | social movement,” Encyclopædia Britannica. 05-Nov-2014.Available:


[x2] K. Appunn, “The history behind Germany’s nuclear phase-out,” Clean Energy Wire, 30-Nov-2018.[Online].Available: https://www.cleanenergywire.org/factsheets/history-behind-germanys-nuclear-phase-out.  [Accessed: 20-Oct-2019].

[x3] R. Hargraves and R. Moir, “Liquid Fuel Nuclear Reactors,” Apsphysics, 2011. [Online]. Available: https://www.aps.org/units/fps/newsletters/201101/hargraves.cfm.                  

[Accessed: 20-Oct-2019].

[xx1]‌ Shizuyo Sutou, Mohan Doss, Ph. D, and Hiroshi Tanooka, Fukushima nuclear accident : global implications, long-term health effects, and ecological consequences. New York: Nova Publishers, 2015.Available:


[xx2] Tokyo Electric Power Company, “The Development of and Lessons from the Fukushima Daiichi Nuclear Accident,” Tokyo Electric Power Company, Mar. 2013.Available:


https://www.researchgate.net/publication/323612656_Analysis_of_Possible_Causes_of_Fukushima_Disaster What is this? What is this used for?

[xx3]https://www.neimagazine.com/features/featuredefence-in-depth/featuredefence-in-depth-431134.html i need a better link for this i can’t find the date of publishing

[xx4]World Nuclear Association, 2017; Cabinet Office, 2018. Where is the link?

[xx5] N. Behling, M. C. Williams, T. G. Behling, and S. Managi, “Aftermath of Fukushima: Avoiding another major nuclear disaster,” Energy Policy, vol. 126, pp. 411–420, Mar. 2019.


[xx6] H. Ohto et al, “From Devastation to Recovery and Revival in the Aftermath of Fukushima’s Nuclear Power Plants Accident,” Asia-Pacific Journal of Public Health, vol. 29, (2_suppl), pp. 10S,2017.Available:


[xx7] The Sasakawa Peace Foundation, “The Fukushima Nuclear Accident and Crisis Management -Lessons for Japan-U.S. Alliance Cooperation,” Sep. 2012.Available: https://www.spf.org/en/_jpus_media/img/investigation/book_fukushima.pdf

[go look at page 160-180 for the timeline] [11]東京電力株式会社(Tokyo Electric Power Company), “Fukushima Nuclear Accident Analysis Report,” Tokyo Electric Power Company, 2012. Available:



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