Showing posts with label Japan. Show all posts
Showing posts with label Japan. Show all posts
Thursday, March 17, 2011 Tags: , , , , , 2 comments

Fukushima might be worse than Chernobyl


damaged reactors no. 1 and 3 of  Fukushima Daiichi nuclear plant

Japan’s nuclear crisis appears to be spiraling out of control. “This is a slow-moving nightmare,” said Dr. Thomas Neff, a physicist and uranium industry analyst at the Massachusetts Institute of Technology. Emperor Akihito described the crisis in his country as “unprecedented in scale”. The radiation level is increasing day by day. So far 315 thousand residents of Fukushima and nearby areas are spending cold nights at evacuation areas. Should our worst fear realize could this be worse than Chernobyl?

The accident that happened in Chernobyl plant near the town of Pripryat in Ukraine, then part of the USSR on April 26, 1986 is considered the worst accident in nuclear history and is categorized under level 7, the highest on the International Nuclear Event Scale. It occurred because of operator’s error on what was supposed to be a routine system test, a series of mistakes that which have led to the tragedy.

The crisis in Fukushima Daiichi nuclear power plant that is unfolding now is a result of a series of natural disaster, first a magnitude 8.9 earthquake, followed by a raging tsunami. The generators that should have supported the emergency cooling system failed to work after having been immersed in water. This had caused the overheating of the fuel rods.

The containment that is made to protect the core from being exposed to the environment have suffered damages from the explosions in the past few days. Is it still capable of serving its purpose?  Maybe not.

The company that is manufacturing the containment vessel of the reactors is GE .  Dale Bridenbaugh, a former GE electric engineer, revealed in an interview with CNN that he resigned from the company 35 years ago due to safety concerns over the containment design. (Fukushima Daiichi nuclear plant's reactors were commissioned from 1971 to 1978. It is one of the oldest nuclear facility in Japan.) 

Graphite which is combustible was responsible for the fire in Chernobyl. Based on the absence of this material on the Japanese reactors experts are saying that there cannot be a repeat of Chernobyl here. Nonetheless, it might not have graphite but it has caesium. This element is highly-pyrophoric. It ignites when combined with water. Hence the chain of violent hydrogen gas explosions that that have caused leakage of radioactive particles into the atmosphere.

The effect of the Chernobyl accident was enormous. According to World Health Organization the radiation release from the Chernobyl accident was 200 times that of Hiroshima and Nagasaki combined. Large areas of Russia, Ukraine and Belarus had been contaminated with radiation. Moreover, the radioactive fallout extended beyond the borders of the former Soviet Union. Except for the Iberian Peninsula, increased amount of radiation had been detected all over Europe. Over 336,000 people were displaced. Among the 600 emergency workers who mitigated the fire, 134 suffered from Acute Radiation Syndrome (ARS). 28 of the fatalities were attributed to ARS, 2 from the immediate explosion. Increased thyroid cancer incidence was noted. According to the 2006 report of the UN Chernobyl Forum's 'Health' Expert Group about 4000 cases of thyroid cancer were diagnosed in children and adolescents (0–18 years) from1992 to 2000, in Belarus, Russia and Ukraine. After the disaster, four square kilometers of pine forest in the immediate vicinity of the reactor turned reddish-brown and died, earning the name of the "Red Forest". Some animals in the worst-hit areas also died or stopped reproducing.

In Chernobyl’s case was only one reactor malfunctioned. At Fukushima plants four reactors are in trouble.  In the advent of simultaneous and complete meltdown of the cores of these reactors, that would be Chernobyl fourfold.  That is simply unimaginable. Let’s cross our fingers it won’t happen.

References:
  1. Caesium. Wikipedia 
  2. Chernobyl Disaster. Wikipedia 
  3. Chernobyl Accident. World Nuclear Association 

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Monday, March 14, 2011 Tags: , , , , , , 1 comments

Japan bracing for the worst, a nuclear meltdown

second explosion at Fukushima Daiichi nuclear plant 

On a televised news conference Prime Minister Naoto Kan described the ongoing crisis in his country as the “the toughest Japan has ever encountered in 65 years since World War II”. Recovery of the nation from the aftermath of the March 11 earthquake and tsunami is being hampered by a series of nuclear events. On Saturday people were stunned by a blast from unit 1 of Fukishima Daichi nuclear power plant. Apparently, it was a hydrogen explosion that resulted from the effort to reduce pressure from the said reactor vessel. There were also reports of failure of the cooling system of reactors of unit 2 and 3 also. Yesterday news came out of increased radioactivity within the Onagawa nuclear facility, located northeast of Fukushima.

“There is a possibility of a meltdown”, said Toshihiro Bannai,  director of the International Affairs Office of Japan’s Nuclear and Industrial Safety, in a telephone interview with CNN.  

Meltdown is a very serious nuclear accident that happens when a reactor lose its coolant. As a result the core with its fuel rods overheats and liquefies. The melted material could potentially leak into the environment, releasing radioactive substances.  Classic examples of meltdown are the Three Mile Island accident, referred as partial core melt and Chernobyl disaster.

Japan is financially endowed, yet deprived of natural resources.  The nation had no option but to rely on imports. 80 percent of energy supply comes from its foreign partners. But to secure economic stability Japan needed to diversify its sources. Nuclear power seemed an attractive solution. Why? Operational cost of a nuclear plant is less compared to conventional types.1-million kilowatt of the former requires 30 tons of fuel per year versus 1.4 million tons of oil needed to fuel the latter. Aside from that, in contrast to coal, natural gas and crude oil, nuclear plants produce no harmful emissions, such as nitrous oxide, sulfur oxides and carbon dioxide.  Therefore, in the 1960’s Japan began formulating a nuclear program. Tokai nuclear plant was the first, built in 1966. Presently 55 nuclear facilities are scattered all over its territory.

schematic diagram of nuclear power generation

A nuclear reactor is a device that initiates and controls a sustained nuclear chain reaction, while the core of the reactor contains all of the nuclear fuel, such as uranium and generates all of the heat. This heat is used to raise steam, which in turn runs turbines that generates electricity.

Fukushima power plant is equipped with boiling water reactor, a type of light water reactor. It uses normal water that acts as coolant, neutron moderator and steam source for the turbines. The reactors are housed in a containment vessel that separates it  from the outside environment.


During the earthquake on March 11 operating reactors 1, 2, and 3 went into automatic shutdown. In cases like this, the coolant plays an important role in removing the decay heat, produced by the fuel rods.  However, to operate the cooling system power supply is needed. The problem was that the power grid and the generators sustained damage due to the quake and the ensuing tsunami. Batteries were used instead to run the system but it could only last for 8 hours. Precious time was lost before back-up batteries were sent to restore cooling. This was critical to the events that followed.



The following day the government declared a state of emergency at Daiichi unit. Signs of overheating of the reactors were already noted. At Unit 1 the pressure had risen to twice the normal level. Tokyo Electric Power Co., which operates the six-reactor Daiichi site, also later announced the it had lost its cooling ability at a second reactor there and three units at its nearby Fukushima Daiini site. Authorities have detected increased radioactivity, eight times the normal levels outside the facility and 1,000 times normal inside Unit 1's control room. Hence forced evacuation was ordered from 3 to 10 kilometers of the plant.

Japanese are now working furiously to avert a meltdown. Seawater and boric acid are being injected to the core via a fire pump.  “This is an indication how serious the problem is. The Japanese had to resort to unusual and improvised solutions to cool the reactor core”, says Mark Hibbs, a senior associate at Nuclear Policy Program for the Carnegie Endowment for International Peace

Until now the Japanese are still struggling to control the situation. An explosion, shattering the building of a second reactor was reported today. A huge plume of black smoke rising in the sky was seen from afar.


In worst case scenario, can we see another Chernobyl here? “There can be no Chernobyl-like disaster at the nuclear plant in Japan, since there is no graphite there, so there is nothing to burn there," said Yevgeny Velikhov, a Russian academician from Kurchatovsky Institute 

The world is sharing the fear of the Japanese people. A meltdown could have a global impact. Everyone is watching closely. 

References:

  1. For battered Japan, a new threat: nuclear meltdown. Yahoo news
  2. Meltdown may be occurring at nuclear plant, Japanese official says. LA Times
  3. Meltdown - What it is and is not. Nucleartourist
  4. Nuclear meltdown. Wikipedia 
  5. Chernobyl disaster. Wikipedia
  6. Three Mile Island Accident. Wikipedia 
  7. Why Japan needs nuclear power. Japannuclear
  8. Location of nuclear power plants in Japan. Japannuclear
  9. Nuclear reactors. What is nuclear
  10. Light water reactor. Wikipedia 
  11. Boiling water reactor. NRC 


Related article:


Earthquake and tsunami may cause Japan a nuclear disaster






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