It has been nearly two months since the earthquake and tsunami hit the east coast of Japan, which resulted in significant damage and loss of life. These events are not unheard of or expected in Japan, however the recent ones have had some dramatic consequences in regards to radiation exposure for some of the country's population, food and also a serious incident for at least one of the country's nuclear reactors. The nuclear reactor plant at Fukushima Daiichi has now had three of its reactors having confirmed meltdowns.
You may ask, what is a nuclear meltdown? Basically, this is just a term used to describe a severe nuclear reactor incident, where the core of the reactor has been damaged due to overheating. They are also generally considered serious because of the likelihood of radioactive material being released to the environment.
As background, a nuclear reactor creates electricity by heating fluids via a nuclear reaction which then powers a generator. This process is done through the use of a cooling system, which takes the fluids that are circulated through the nuclear reaction chamber from that location to a generator. Then the fluid that was circulating through the nuclear reactor chamber and consequently being heated is taken to another section of the power plant. At this location the fluid is used as a heat source for a boiler and in turn the steam is used to drive a turbine driven electrical generator.
The 'reaction chamber' needs a continual supply of cool fluids as the byproducts of the nuclear reaction also create heat and continue to produce heat even after the reaction occurs for a period of time (up to several years). If this chamber doesn't receive fresh supplies of cool fluids a 'meltdown'. In the case of the Fukushima power plant, power was lost at the site after the tsunami hit meaning that the cooling system was not functional for a period of time. The cooling system at the plant could not bring cool fluids to the reactors, causing the system to overheat and in turn resulting in several meltdowns.
One of the human health concerns as a result of these meltdowns is the release of radioactive material. Some reports suggest areas within a radius of 30-50km of the power plant have levels of radioactive ceasium to cause concern and iodine-131 within the seawater discharge. However, other research reports state that areas outside the 20km evacuation zone around the power plant have levels of radiation far below human health concerns. There are however still human health risks associated with the consumption of contaminated food and water.
Despite the relative amounts of radioactive discharge from the site and people's concerns in the areas adjacent to the power plant, it is the power plant workers I feel the most for in this situation. These staff continue to work in this environment, knowing there will be consequences as a result of their constant exposure to radiation whilst attempt to bring these reactors back to some sort of stability. These people are selfless and are reducing the risks that would potentially occur if they weren't so self-sacrificing. Amazing!