About

Hiroshima

The United States detonated two nuclear weapons over the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, respectively, with the consent of the United Kingdom, as required by the Quebec Agreement. The two bombings killed between 129,000 and 226,000 people, most of whom were civilians, and remain the only use of nuclear weapons in armed conflict.

In the final year of the war, the Allies prepared for a very costly invasion of the Japanese mainland. This undertaking was preceded by a conventional and firebombing campaign which devastated 67 Japanese cities. The war in Europe had concluded when Germany signed its instrument of surrender on May 8, 1945, and the Allies turned their full attention to the Pacific theater. The Allies called for the unconditional surrender of the Imperial Japanese armed forces in the Potsdam Declaration on July 26, 1945, the alternative being “prompt and utter destruction”. Japan ignored the ultimatum and the war continued.

By August 1945, the Allies’ Manhattan Project had produced two types of atomic bombs, and the 509th Composite Group of the United States Army Air Forces (USAAF) was equipped with the specialized Silverplate version of the Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. The Allies issued orders for atomic bombs to be used on four Japanese cities on July 25. On August 6, one of the modified B-29s dropped a uranium gun-type bomb (“Little Boy”) on Hiroshima. Another B-29 dropped a plutonium implosion bomb (“Fat Man”) on Nagasaki three days later. The bombs immediately devastated their targets. Over the next two to four months, the acute effects of the atomic bombings killed between 90,000 and 146,000 people in Hiroshima and 39,000 and 80,000 people in Nagasaki; roughly half of the deaths in each city occurred on the first day. Large numbers of people continued to die for months afterward from the effects of burns, radiation sickness, and other injuries, compounded by illness and malnutrition. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.

People on the ground reported a pika (ピカ)—a brilliant flash of light—followed by a don (ドン)—a loud booming sound.[145] Some 70,000–80,000 people, around 30% of the population of Hiroshima at the time, were killed by the blast and resultant firestorm, and another 70,000 were injured. It is estimated that as many as 20,000 Japanese military personnel were killed. U.S. surveys estimated that 4.7 square miles (12 km2) of the city were destroyed. Japanese officials determined that 69% of Hiroshima’s buildings were destroyed and another 6–7% damaged.

Fukushima

The Fukushima Daiichi nuclear disaster (福島第一原子力発電所事故 Fukushima Dai-ichi (About this soundpronunciation) genshiryoku hatsudensho jiko) was a nuclear accident at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima Prefecture. The disaster was the most significant nuclear accident since the 26 April 1986 Chernobyl disaster and the only other disaster since to be given the Level 7 event classification of the International Nuclear Event Scale.

The accident was started by the tsunami following the Tōhoku earthquake on 11 March 2011. On detecting the earthquake, the active reactors automatically shut down their fission reactions. Because of the reactor trips and other grid problems, the electricity supply failed, and the reactors’ emergency diesel generators automatically started. Critically, they were powering the pumps that circulated coolant through the reactors’ cores to remove decay heat, which continues after fission has ceased.[ The earthquake had generated a 13-15 meter high tsunami that arrived approximately 50 minutes later, which over-topped the plant’s seawall, flooding the basements and disabling the emergency generators. The resultant loss-of-coolant accidents led to three nuclear meltdowns, three hydrogen explosions, and the release of radioactive contamination in Units 1, 2 and 3 between 12 and 15 March. The spent fuel pool of previously shutdown Reactor 4 increased in temperature on 15 March due to decay heat from newly-added spent fuel rods; but did not boil down sufficiently to expose the fuel.

The earthquake and tsunami damaged or destroyed more than one million buildings leading to a total of 470,000 people needing evacuation from the surrounding area. Of that number the nuclear accident was responsible for 154,000 being evacuated due to the rising off-site levels of ambient ionizing radiation caused by the release of airborne radioactive contamination from the damaged reactors. A report by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and World Health Organization projected no increase in miscarriages, stillbirths or physical and mental disorders in babies born after the accident.[15] An ongoing intensive cleanup program to both decontaminate affected areas and decommission the plant will take 30 to 40 years, plant management estimate.