Nuclear fission is the process of splitting huge, unstable atoms, usually radioactive uranium 235, by hitting them with neutrons. This process is used to generate energy in nuclear power plants. However, if safety measures are ignored, the uranium fuel in the reactor can overheat and melt through barriers, leading to a nuclear disaster. The Chernobyl nuclear power plant in Ukraine is a prime example of a nuclear disaster.
On April 26, 1986, the RBMK reactor number four at the plant went out of control during a low-power test, causing an explosion and fire that demolished the reactor building and released large amounts of radiation into the atmosphere. The RBMK reactors do not have a containment structure, which is a concrete and steel dome over the reactor designed to keep radiation inside the plant in the event of an accident. As a result, radioactive elements such as plutonium, iodine, strontium and cesium were dispersed over a wide area. In addition, graphite blocks used as moderating material in the RBMK ignited at high temperature when air entered the reactor core, contributing to the emission of radioactive materials into the environment.
Iodine, strontium and cesium were the most dangerous elements released from Chernobyl. Iodine is linked to thyroid cancer, strontium can cause leukemia and cesium affects the entire body and can damage the liver and spleen. These elements have half-lives of 8 days, 29 years and 30 years respectively. Therefore, some of these isotopes are still present in the area to this day.
Radioactive fallout spread across much of the Northern Hemisphere through wind and storm patterns, but the amounts scattered were in many cases negligible. Emergency workers (liquidators) were recruited from the area and helped clean up the plant facilities and the surrounding area. These workers were mostly plant employees, Ukrainian firefighters, and many soldiers and miners from Russia, Belarus, Ukraine and other parts of the former Soviet Union. You can visit the Chernobyl area today, including the exclusion zone which is within a 30-kilometer radius surrounding the plant.
Although some of the radioactive isotopes released into the atmosphere still persist (such as strontium-90 and cesium-13), they are at tolerable exposure levels for limited periods of time. Some residents of the exclusion zone have returned to their homes of their own free will and live in areas with higher than normal levels of ambient radiation. However, these levels are not deadly. On 15 December 2000, the last operating reactor at Chernobyl was closed and decommissioning began.
This involves disposal and disposal of fuel and debris, decontamination of the plant and surrounding area including any soil or water that may be radioactive. There are three retired reactors that will be dismantled at the site which is expected to take several decades under supervision from Ukraine's government with assistance from IAEA providing advice on planning, engineering and administration.