This crippled the cooling systems (in almost all 6 nuclear reactors) needed to keep nuclear fuel from going into full meltdown. That would cause the much feared nuclear explosions resulting in the release of radioactive radiations.

The nuclear accident was the worst since the Chernobyl disaster in Ukraine in 1986, and the worst nuclear crisis in Japan since the atomic bombing of Hiroshima and Nagasaki during World War II. Unlike the Chernobyl explosion which happened in the midst of nuclear reaction; in Fukushima, three reactors were automatically shut down and the reaction stopped when the earthquake occurred. But the failure of the cooling systems in all the six nuclear reactors soon raised the temperatures and pressures rapidly, and to-date (17 March 2011), 4 reactors experienced explosions of different degrees at different stages.

CNN-Google picture showing: the 6 damaged nuclear plants in Fukushima, north-east of Tokyo. Crews have struggled to control since Japan's devastating earthquake and tsunami a week ago, amidst radiation fears in a country racing to avoid a full-on nuclear crisis. Latest fire was discovered Wednesday morning (17-March-2011) in the No. 4 reactor building at the Fukushima Daiichi plant.

Prime Minister Kan said dangerous levels of radiation had spread from four reactors of the Fukushima nuclear plan. Other than the calls to increase the evacuation radius from 10 kms, then 20 kms and finally 30 kms from the epicenter of nuclear catastrophe, details of the information on the causes of nuclear failure, prevalent radiation levels and progress of rectification were limited.

People were frustrated and angry, doubting the level of transparency and fearing the worst case scenario of completely melt down, a disaster that could emit large amounts of  radioactive contamination. Panic swept Tokyo after a rise in radiation levels of 40 times normal levels was recorded. Some locals, tourists and many foreigners scrambled to leave the country, while others stockpiled food and supplies. Multinational companies considered relocation outside Japan. Many countries imposed travel warning to Japan. Other  precautionary measures taken included screening of travelers from Japan, testing of almost all Japanese food imports and banning of certain categories. Shipping industry has become increasingly nervous about sailing into the highly contaminated Japanese waters.

Nuclear experts have been warning that Japan was underplaying the severity of the nuclear crisis. Officials later admitted that at least 3% of the fuel in 3 reactors had been severely damaged, suggesting partial core melt-down. Japan on 18 march 2011 finally acknowledged the 'gravity and severity' of the nuclear crisis. Its nuclear rating agency raised the rating of the nuclear accident from Level 4 to Level 5 on a 7-level international scale. That put it on par with the 1979 Three Mile Island accident.

The International Nuclear Event Scale defines a Level 4 incident as having local consequences and a Level 5 as having wider consequences. This raised alarms at the neighboring countries like China, the Philippines, Korea, Russia, Hawaii and California. By the third week, radiations had been detected over these countries as these radiations drifted across territories.

These series of fires and explosions at the nuclear plants in Fukushima of Japan have revived doubts regarding the growth of nuclear power industry globally. The crisis has prompted many countries to boost safety checks at nuclear plants. European energy officials agreed to apply stress tests on their plants and Germany moved to switch off seven aging reactors. China and Switzerland have announced temporary freeze on new nuclear plants, pending overall safety review.