Japan Teeters on the Edge of Nuclear Meltdown, While U.S. and Other Countries Work to Build More Nuclear Reactors

On Friday, Japan was hit by a massive earthquake initially measured to be 8.9 and now upgraded to 9.0 on the Richter scale. One of the largest quakes ever measured in history, its epicenter lay just northeast of Japan. The quake unleashed a massive tsunami. Together, the quake and tsunami have claimed more than 10,000 lives.

Then, on Saturday an explosion occurred at the Fukushima Daiichi nuclear power plant. Located in northeastern Japan, near the quake's epicenter, the plant has six boiling water reactors. The first blast occurred at Fukushima No. 1. In order to keep the reactor cool, the system needs a regular influx of water. This water system, in turn, requires electricity. The generators were wiped out by the tsunami. Replacement generators were delivered but their plugs were incompatible with those of the plant.

Desperate attempts were made to keep the reactor's core cool by drawing on sea water. If the core is not kept cool, it can melt through the containment wall, causing a meltdown and allowing radiation to leak. (For more about the structure of the reactor, see an image of the Fukushima reactor's design.)

Earlier on Monday, an explosion took place at reactor No. 3, whose core officials are now also struggling to keep cool. Then, early Tuesday an explosion was reported at No. 2. "Government officials admitted that it was 'highly likely' the fuel rods in three separate reactors had started to melt despite repeated efforts to cool them with sea water," reported Gordon Rayner and Martin Evans for the Telegraph. "Safety officials said they could not rule out a full meltdown as workers struggled to keep temperatures under control in the cores of the reactors."

Japan has formally called on the international community for assistance to address the problem.

As a result of Friday's earthquake and tsunami in Japan, leaders worldwide are rethinking their nuclear energy policy.

While some are reconsidering their safety mechanisms, others are radically scaling back. China and Russia, however, are considering building new reactors. 

According to the International Atomic Energy Agency (IAEA), 442 nuclear power plants are currently in operation.

The largest consumers of nuclear energy are -- in order of megawatts consumed -- the U.S., France, Japan, Russia and Germany, followed closely by South Korea, Canada, the Ukraine, the United Kingdom and Sweden.

But as growing economies are building new plants, these rankings will soon change. Given plants under construction, the biggest consumers are set to be: China, Russia, South Korea, India, Japan, Bulgaria, Ukraine, France, Finland, Brazil and the U.S.

Here's a quick overview of the state of nuclear energy worldwide, focusing on its biggest consumers:

China: On Monday, China -- the biggest consumer of energy worldwide but currently still well behind other nations in the amount of megawatts of energy drawn from nuclear power -- announced its continued commitment to nuclear energy. To date, China has 13 nuclear reactors. A further 27 new reactors are currently under construction and another 50 plants are planned. 

Russia: According to the Interfax news agency, Russian Prime Minister Vladimir Putin stated on Monday that Russia would continue with construction of 20 planned nuclear power plants. Russia is currently ramping nuclear energy from 16 percent to 33 percent of the overall energy budget. Russia has a vexed relationship to nuclear energy as a result of the nuclear meltdown in 1986 in Chernobyl, located in what was then the Soviet Union and is now the Ukraine.

India: Prime Minister Manmohan Singh announced Monday that all of India's nuclear reactors will be proofed for security, particularly with regard to earthquakes and tsunamis. India has over 20 nuclear power plants, the majority of which are along its coast.