An earthquake that released 9.0 magnitude waves was followed by a subsequent tsunami that killed hundreds of people, caused buildings and ships to be washed away from shore, and triggered a series of massive fires. Hundreds of people are dead and thousands remain missing. Now, Japanese civilians must also face the aftermath of what is now possibly considered to be the worst nuclear incident since the 1986 explosion of an entire nuclear reactor at the Chernobyl power plant in Ukraine.
As of April 12, over 370,000 terabecquerels (370,000 trillion basic units used to measure radioactive emissions) of radioactive iodine and cesium have been released into the atmosphere from the Fukushima-I power plant. The area within a 20km (12 mile) radius of the power plant has been closed off as an evacuation zone in order to reduce the damage done by nuclear emissions. As of April 21, the Japanese government declared this area a no-go zone. Residents who violate this sanction will be fined or detained.
How were such massive amounts of nuclear radioactive substances released? When the earthquake first hit on March 11, three of the plant’s six reactors had already been shut down in preparation for maintenance procedures. As the earthquake’s seismic waves reached the power plant, the waves interfered with the electric power that was being used as the reactors’ energy source. The reactors possessed diesel generators, which were then immediately switched to as the backup supply source. However, these generators were likewise shut down by tsunami waves. As this occurred, the water supply in the reactor cores was reduced, which turned into steam circulating throughout the reactor. The steam in one of the reactor units carried hydrogen — a highly flammable and explosive gas in the presence of oxygen — which blasted the roofs off of two reactor units. It was this blast that was believed to have opened the initial pathway for radioactive substances within the reactors to be released into the atmosphere. Subsequent fires in other reaction units followed, possibly burning any unspent fuel that was still contained within the reactors.
In spite of the large amounts of emissions released after the blasts, health risks for workers and civilians within the evacuation zone remain indeterminate. Following the Chernobyl disaster, many civilians that lived within 19 miles of the power plant developed thyroid cancer as a result of exposure to iodine-131, a radioisotope of iodine that targets the thyroid. No health risks of such severity have yet been found among Japanese civilians who live within close range of the Fukushima power plant. It is believed that most of the radioactive substances were released directly released into the atmosphere following the initial steam blasts. Nevertheless, civilians who live within a 20km radius to the power plant are urged to stay away from the area for safety concerns.
Current problems resolving the damage that was done to the reactors involve removing spent fuel rods from the reactor units’ storage pools. Unless these fuel rods are removed, the storage pools will remain open and will continue to allow radioactive substances to leak out of them. Boron-containing water must also be frequently added to the reactors’ supply pools, so that water levels do not become low enough to cause steam blasts to happen again. Earthquakes of smaller magnitude than the initial March 11 earthquake are also reoccurring.
Other methods being utilized to minimize the amount of radioactive emissions include pumping nitrogen gas into containment vessels within the reactors to prevent explosions and installing silt screens and steel plates at sites of leakage. The nitrogen gas is injected in order to prevent hydrogen gas from accumulating within the reactor. If hydrogen levels were to become high enough, explosions would occur as the hydrogen reacts with the oxygen gas within the atmosphere.
As of April 11, the extensively high concentrations of nuclear emissions have placed the Fukushima power plant to be at Level 7 of the International Nuclear and Radiological Event Scale (INES). This is the highest level of danger that an accident that triggers nuclear emissions can attain. It also indicates that the radioactive emissions are high enough to present an international threat. The Fukushima explosion is now considered to be the first level 7 accident since the Chernobyl fires. It is also the second disaster to attain a level 7 rating to this date.
