Chernobyl, an Examination of the World’s Worst Nuclear Disaster
On the 26th of April, 1986 unit 4 of the Chernobyl nuclear power station was taken off the electrical grid to perform an experiment in which the reactor would be run at low power. The Chernobyl power station, which is located in the present day Ukraine and is approximately 12 miles south of the border with Belarus, did not react as designed and unit 4 proceeded to spiral out of control. The unconstrained fission reaction which followed resulted in a steam explosion that poured radioactive material into the atmosphere. To this day Chernobyl is the largest and farthest reaching nuclear disaster in human history.
The meltdown of Chernobyl's fourth reactor was the result of a series of errors in the reactor design, operations, and a failure to follow established safety protocols. These human errors resulted in more than 400 times the radioactivity of the Hiroshima nuclear bomb being released into the environment (Salge & Milling, 2006). This caused a massive economic, environmental, and human toll to the region. Improved reactor design and proper adherence to safety procedures could have prevented this disaster.
The Chernobyl disaster was caused by two part human error. The first part occurred long before the 26th of April and was due to the design of the reactor. The Chernobyl reactors create energy by utilizing thermal energy from the fission of the uranium-235 isotope to heat water into steam. The steam then turns turbines which create electrical energy. The problem with the Chernobyl reactor is the way it maintains the fission reaction.
The fission of uranium-235 creates neutrons which in an ideal situation bombard other uranium-235 atoms which then divide and continue the process by releasing more neutrons. Unfortunately in its naturally occurring state uranium is made up 99.3% of uranium-238 (Salge & Milling, 2006). The neutrons produced from dividing uranium-235 are very high energy and tend to be absorbed by the uranium-238. The uranium can either be enriched which is extremely expensive, or the neutrons can be dropped to a lower energy state by passing them through a substance known as a moderator.
To save on costs Chernobyl did not use enriched uranium and instead used graphite as a moderator. Most western reactors use water or heavy water as a moderator. The advantage of this is that when the water boils into steam less water remains to moderate the reaction and the fission slows down. The disadvantage of water is that it is not a very good moderator and works best with enriched uranium. The former Soviet Union is the only country that built graphite moderated nuclear reactors. In a graphite moderated reactor as the reactor heats up more water is turned into steam causing the graphite to heat up which increases its effectiveness as a moderator. This in turn speeds up the reaction and without intervention the reactor will spiral out of control (Salge & Milling,...