Michael Nicolos
10/16/14
International
WWII Nuclear Retaliation
On December 7, 1941, military personnel stationed in Hawaii awoke to one of the biggest tragedies the United States has ever known. 353 Japanese Fighters, Bombers, and Torpedo planes took to the skies that day to lead a preemptive attack upon Pearl Harbor in an attempt to deter the U.S. Pacific Fleet from interfering with the Japan Empire's plan to control Southeast Asia and its resources. The attack began at 7:48 am on a Sunday morning and ended 3 hours later in devastating fashion. Among the wreckage were 8 battleships, including the first one struck, the Arizona. With a total of 188 aircrafts destroyed, 2,402 men killed and 1,282 wounded by the swift attack, the United States officially declared war on the Empire of Japan the very next day. After 4.5 years of destruction known as the Pacific War, the United Kingdom, Republic of China, and United States called for a surrender of Japan, threatening “prompt and utter destruction” should Japan not comply. Japans refusal to yield led the United States to detonate two atomic bombs over Japan; one in Hiroshima, a major military site located in a suburban city, and one in Nagasaki, a heavy industrial site and home to one of Japans largest seaports. An estimated 200,000 people died or were injured as a result of the bombings in August of 1945. The atomic bombs themselves differed in material composition. The bomb dropped over Hiroshima, ironically named “Little Boy,” used Uranium-235 as the primary form of fissionable material while the bomb dropped over Nagasaki, appropriately named “Fat Man,” used Plutonium-239 as the primary form of fissionable material. Though different, the two atomic bombs used the same method of “chain reaction” to prepare the bomb before exploding. Uranium-235 (U-235), first discovered as being a fissionable isotope of Uranium by Niels Bohr and John Wheeler5 , is one of the few materials on Earth that can undergo induced fission. By shooting a neutron at it's nucleus, U-235 will break apart into two smaller particles while emitting more neutrons. Because U-235 freely accepts stray neutrons and produces more than the amount it requires to fission, a chain reaction can take place. Note: U-235 is a rare element, therefore a sample of Uranium must be enriched to create weapons-grade Uranium which is at least 90% U-235. In order to weaponize U-235 and create the “Little Boy” atomic bomb, scientist placed a sphere of sub-critical mass U-235 (to prevent premature detonation) around a neutron generator on one side of a long tube and a bullet of U-235 on the other with explosives behind it. Once an attached barometric-pressure sensor hits the predetermined height, the explosives go off, the U-235 bullet is propelled down the barrel striking the sphere and generator, initiating the chain reaction causing and intense explosion that emits heat and gamma radiation. As an additional fuel for nuclear warfare, Plutonium was discovered in 1941 at the University of Berkeley. Plutonium-239 (Pu-239) was found to be the most efficient isotope of Plutonium for initiation of a chain reaction of the material via fission. Instead of firing a bullet of U-235 to initiate the reaction, scientist bounded a sphere of Pu-239 with Beryllium to create free neutrons, and layered it with explosives to create an implosion triggered reaction. Once the explosives are detonated, a shock wave condenses the sub-critical material into super-critical mass initiating fission and resulting in a catastrophic explosion. With an explosive yield of 23 kilotons, the “Fat Man” bomb proved to be a more devastating weapon than its predecessor the “Little Boy” that only yielded 14.5 kilotons; however, the “Fat Man” had a much higher fission efficiency rate at 17% than that of the “Little Boy” at 1.5%. In any case, both these weapons made the two, once thriving, Japanese cities uninhabitable for years and brought an end to the Pacific War days thereafter.