Although not yet in a full meltdown status, nuclear reactors at the Fukushima Daiichi station in Japan is now at a very critical status. Japanese officials rated earlier the accident as a level 4 “accident with local consequences” as per the International Nuclear and Radiological Event Scale’s (INES) 7-tier nuclear crisis scale.
Nuclear energy is basically an upscale water boiling process, where a self-sustaining nuclear chain reaction sustains heat to boil water, driving steam turbines and then electricity. Japan has 54 nuclear reactors, making it the third-largest user of nuclear power in the world, only after the US and France. Six of these reactors are housed in the Fukushima Daiichi station, which was commissioned in the 1970s.
Since the March 11 earthquake and tsunami, reactors at the Fukushima Daiichi station are considered seriously crippled: explosions occurred at Unit 1 and 3 which destroyed exterior walls, most probably due to buildups of hydrogen gas produced by the zirconium in the fuel rods reaction with coolant water at extremely high temperatures. As of March 15, a third explosion has occurred at reactor No. 2, which seems that the containment vessel had been seriously breached.
How do you turn off a nuclear reaction?
Nuclear reactors work by harnessing the process of nuclear fission: the splitting of an atom into two smaller atoms, which also yields heat and send neutrons flying. Another atom absorbs one of the neutrons, which itself becomes unstable and releases more heat and more neutrons. To stop this process, the runaway neutrons must be intercepted. Control rods made of materials that absorb neutron do this interception.
Once the reactor is stopped, it still exhibits an enormous amount of heat, especially due to the by-then split uranium atoms those themselves give off so much heat. In the case of Japan, the disaster caused blackouts that cut off the externally sourced AC power for the reactor’s cooling system. The facility’s backup diesel generators also failed after the blackout, exposing the reactor to untamed heat and in serious situation of overheating.
Because of these dangerous developments, the crisis at the Fukushima Daiichi plant now ranks as the second most serious nuclear power plant accident after Chernobyl (Soviet Union 1986).
Effects on human health
Humans are exposed to radiation on a daily level, albeit in low levels. They occur naturally in sunlight, as well as human-made like X-rays, cancer treatment, nuclear weapons, and nuclear power plants.
Exposure to radiation starts to be dangerous with the amount and duration of exposure. Over a short period, significant exposure can cause burns or radiation sickness. Symptoms include nausea, weakness, hair loss, skin burns and reduced organ function.
Long term effects include skin cancer, cataract, mutation of human fetuses or unborn children which when born will have smaller brain and head size, abnormal eyes, slow growth, and mental retardation.