The disaster of the Fukushima nuclear plant continues to shake international energy discussion. On March 11, 2011, a 9.0 earthquake, followed by a tsunami with waves over 120ft led to Fukushima Daiichi Power Plant suffering great damage. Followed by this catastrophe, 3 generators experiencing a level 7 meltdown. After gone through some research, I can say that TEPCO should have taken more adequate safety steps but failed to do so, and therefore from my point of view, this devastating damage was purely due to human error.
Firstly, the Fukushima Daiichi Plant was problematic. It was built close to the shore and about 33 feet (10 meters) above a coastline that has experienced numerous tsunamis over the centuries, including three within the last 120 years whereby all of them smaller than the one on March 11. The height was a level regulators and the utility operator thought it was safe. But unfortunately, the tsunami was at least 46 feet (14 meters) tall and it knocked out the plant's power as well as the emergency generators, located in the basement areas of the reactor buildings, disabling their cooling systems and sending three active reactors into meltdowns. The plant was placed so low in assumption there was no need to anticipate major tsunami.
Next, is the major damage to piping and other safety significant structures at Fukushima Daiichi Unit 1, the oldest reactor at the site is the cause of the first meltdown, even before tsunami hit. The rush water from the tsunami disabled the cooling mechanism designed to prevent the meltdown. The pipe which regulates the heat of the reactor and carrying coolant rupture and therefore it doesn't get to the core. Previously, the author of TEPCO, Katsunobu Onda had mentioned that if "TEPCO and government of Japan admit earthquakes can do direct damage to the reactor, this raises suspicions about the safety of every reactor they run. They are using a number of obsolete reactors that have the systematic problems such as wear and tear on the piping. Besides that, TEPCO admitted in covering up data concerning cracks in critical circulation pipes. These pipes are there to draw off the heat from the reactor. If these pipes were to fracture, it would result in a serious accident such as leakage of coolant. These are the highly important safety pieces of equipment. Evidence stated that, cracks were found in the Fukushima Daiichi Power Plant, reactor one, reactor 2, reactor 3, reactor 4 and reactor 5. The cracks in the pipes were not due to earthquake damage but came from simple wear and tear of long term usage.
Moreover, poor inspections and layout also lead to such phenomenon. According to several engineers who worked at TEPCO plants mentioned that the often piping would not match up the way it should according to the blueprints. In that case, the only solution was to use heavy machinery to pull pipes close enough together to weld them shut. Inspection of piping was often cursory and the backs of the pipes, which were hard to reach, were often ignored. The inspections themselves were generally hasty and done by visual checks, and therefore it was easy to be ignored. Repair jobs were rushed as no one wanted to be exposed to nuclear radiation longer than necessary. The power plant scattered with web of pipes and it was not arranged as in safety layout.
Ignorance of TEPCO on the warning of tsunami and Fukushima also had lead to this double disaster. A review of company and regulatory records shows that Japan and its largest utility repeatedly downplayed dangers and ignored warnings. The research paper were presented at a nuclear engineering conference in Miami in July 2007 concluded that there was a roughly 10 percent chance that tsunami could test or overrun the defences of the Fukushima Daiichi nuclear power plant within a 50 year span based on the most conservative assumptions. Even the Tokyo Electric scientist realised that it was quite possible a giant wave would overwhelm the seawalls. However, they did nothing to change its safety planning based on the study.
Other cause of this disaster might be the explosion of gas tanks at the site after the earthquake. The outside of the reactor building suffered structural damage. Furthermore, the workers are less skilful as the plant had problems in abundance and the approach taken was piecemeal. As for most of the critical work such as construction work, inspection work and welding were entrusted to sub-contracted employees with little technical background or knowledge of nuclear radiation.
2. Carefully observed the industrial process and operation of the Fukushima nuclear plant.
The process is called "Nuclear Fission", it is a reaction between a free neutron that hits a Uranium atom. The Uranium absorbes this neutron, goes into an unstable state and explodes. This process repeats itself over and over every time the Uranium splits, new free neutrons are released and react with other Uranium atoms.
Nuclear reactors are mainly divided into 3 ways of operation. Critical mass, subcritical mass and supercritical mass. It is used to determine how stable the temperature of the core will be depending on the uranium atom's form inside. In general nuclear power plants require a combination of critical and few supercritical mass to be able to rise and lower the temperature depending on the electricity required.
Operation inside the plant consists of the reactor which is a collection of long rods filled with Uranium bundled together. These bundles are put into a pressure vessel and submerged into something similar to a very deep swimming pool (water acts as a coolant). Uranium on it's own would overheat almost instantly, thus control rods made of materials that can absorb these neutrons are placed inside and can be raised or lowered depending on the present reactions inside the core. Making sure the temperature can be controlled at all time.
The heat produced by the reactor's core produces steam, this steam is used to drive a turbine where spinning electricity generators produce the power you can use in your home. Different ways to cool down nuclear reactors, some work on water, some on liquid metals, some are cooled by gas, depending on how productive you want the cores to become. " http://www.youtube.com/watch?v=LTnfXLws40Q"
3. Evaluate the impact of the Fukushima nuclear disaster to the society, ecology, sociology and health.
Society: A major footprint has left inside the people's heart and the society in Japan, Citizens have taken up a number of new strategies and tactics in opposing nuclear power in Japan. Most obviously, mass protests of forty thousand and more participants in such public events have become commonplace, including the Sayonara Nuclear Power rallies headlined by well-known public figures such as Kenzaburo . These rallies have drawn out tens of thousands of new marchers and participants who a decade ago felt little interest in marching against atomic energy.
Ecology: At least 1,000 square kilometers of land much of it forest and farms has been cleaned up as workers power-spray buildings, scrape soil off fields, and remove fallen leaves and undergrowth from woods near houses. The goal is to make all of Fukushima livable again. But as scientists, engineers, and ordinary residents begin this massive task, they face the possibility that their efforts will create new environmental problems in direct proportion to their success in remediating the radioactive contamination.Fukushima Dai-ichi Nuclear Power Plant caused a massive release of radioactive materials to the environment where it influences on living organisms that could ultimately produce long-term destruction of ecosystems and cause chronic diseases.
A few studies have been performed to date, "In the case of the Chernobyl accident, changes in species composition and phenotypic aberration in animal and an increase in the incidence of thyroid and lymph cancers in humans18 have been reported."
Sociology:
The accident displaced about 100,000 people who lived near the plant and has raised fears on contamination in everything from fruit and vegetables to fish and water. Even though government declared the plant was stable, it estimates that it will take about 40 years to completely neutralize the plant.
Failure of the cooling system at the Fukushima Nuclear Power Plant intensified the situation, resulting in evacuation of about two hundred thousand people residing around the plant.
The tourism sector will be deeply effected due to the radioactive, whereby the food industry will be lacking in exports. People around the globe couscous about the radiation of nuclear contaminated the atmosphere.
4. Outline the actions taken by Tokyo Electric Power Company (TEPCO), government and the regulatory body during the occurrence of the Fukushima nuclear disaster.
The Japanese reaction occurred after the Fukushima Daiichi nuclear disaster. A nuclear emergency was announced by the government of Japan on 11 March. The Prime Minister Naoto ordered that people within a 20 km around the Fukushima Daiichi nuclear plant must leave, and urged that those living between 20 km and 30 km from the site to stay indoors. The groups were also urged to evacuate on 25 March. Japanese authorities have admitted that lax standards and poor oversight contributed to the nuclear disaster.
They have come under fire for their handling of the emergency, and have engaged in a pattern of withholding damaging information and denying facts of the accident. Authorities apparently wanted to "limit the size of costly and disruptive evacuations in land-scarce Japan and to avoid public questioning of the politically powerful nuclear industry". There has been public anger about an "official campaign to play down the scope of the accident and the potential health risks". The accident is the second biggest nuclear accident after the Chernobyl disaster, but more complex as all reactors are involved.
Prime Minister Naoto took an instant anti-nuclear stance in the following months of the Fukushima disaster. In May, he ordered the aging hamaoka nuclear power plant be closed over earthquake and tsunami fears, and said he would freeze plans to build new reactors. In July 2011, Mr. Kan said that "Japan should reduce and eventually eliminate its dependence on nuclear energy saying that the Fukushima accident had demonstrated the dangers of the technology". In August 2011, the Japanese Government passed a bill to subsidize electricity from renewable energy sources. An energy white paper, approved by the Japanese Cabinet in October 2011, says "public confidence in safety of nuclear power was greatly damaged" by the Fukushima disaster, and calls for a reduction in the nation's reliance on nuclear power. As of August 2011, the crippled Fukushima nuclear plant is still leaking low levels of radiation and areas surrounding it could remain uninhabitable for decades due to high radiation in the atmosphere.
5. Propose effective preventive action to be strengthened by Tokyo Electric Power Company (TEPCO) in re-examine the nuclear plant safety.
Effective lesson need to be learned by TEPCO in order to prevent the recurrence of such disaster in future. There are few preventive actions can be addressed due to the accident.
Strengthen measures against earthquakes and tsunamis
Inadequate preparedness against large tsunamis, including failure to adequately envisage the frequency of occurrence and the height of tsunami cause the nuclear accident. A criteria for safety design of structures need to be taken into consideration that allows for the impact force of tsunami waves.
Ensure reliable cooling function of reactors and PCVs
The loss of cooling functions of the reactors and the PCV worsening the accident. So in order to bring the reactor to a state of cold shutdown as early as possible the operators should secure seawater cooling pumps as well as installing large-sized air-cooled emergency generators. As for future efforts TEPCO plan to make seismic reinforcements of large sized freshwater tanks and related efforts.
Thorough accident management measures
TEPCO should enhance accident management measures since there are insufficiencies were found during the accident. The piping system which are obsolete needs to be upgraded and inspection need to be done from time to time. Moreover, the accident revealed in the area of responses to accidents at sites having multiple units and the development of the accident at one reactor affected the emergency responses to the accident in neighbouring rectors. Therefore, the measures to ensure the engineering independence of each reactor at sites having more than one reactor need to be planned.
Consideration of NPS arrangement in basic design
Response to the accident becomes difficult since the spent fuel storage pools were located at a higher part of the reactor building. Therefore, sufficient consideration of an adequate layout for the facilities and buildings of NPSs is required at the stage of basic design for new construction.
Improvements to the accident response environment
After the disaster, the radiation dose in main control room increased whereby this unable the operating staffs to enter the main room. Therefore, planning to enhance function at emergency stations, seismically reinforce office buildings.
Enhancement of training for responding to severe accidents
Effective training responding to such accidents has not sufficiently implemented in the past. Therefore, workers must be given an intensive training and also implement nuclear emergency drills to prepare for the occurrence of severe accidents. The government plans to engage in support and cooperation such as necessary advice for the drills performed by authorities.
