Caesium-137 was more hazardous long-term, with a half-life of about 30 years. This radioactive element has a half-life of eight days.

Most radiation exposure that occurred shortly after the accident was caused by Iodine-131. Some of the most dangerous radioactive elements released into the atmosphere after the explosion included iodine, caesium, and strontium. The CEZ is known as the area within 30 kilometers of the plant. Some elements had shorter lives, while others were still present within the Chernobyl Exclusion Zone (CEZ). The Unit 4 reactor explosion released more than 100 radioactive elements into the environment. Radioactive Materials Released into the Environment Map of the radionuclide deposition of caesium-137 in Chernobyl and surrounding areas, via United Nations Scientific Committee on the Effects of Atomic Radiation Within the first few weeks of clean-up, 28 individuals died as a result of Acute Radiation Syndrome (ARS) due to high amounts of radiation exposure. In 19, about 240,000 emergency workers were called in to help clean up the site. Within three weeks of the accident, about 116,000 people living within a 30-kilometer radius of the Chernobyl plant were relocated to less contaminated areas. Within 36 hours of the accident, about 49,000 residents in the nearby town of Pripyat were evacuated from the area. One operator died when the explosions occurred, and another died in the hospital hours later as a result of injuries. This process took place for about nine days. Thousands of tonnes of sand, clay, boron, and other materials were dumped onto the reactor core to extinguish the fire at the core and prevent the release of any more radioactive particles. Injecting water into the reactor was halted after concerns grew over water possibly leaking into the Unit 1 and 2 reactors. Throughout the day of April 26, hundreds of tonnes of water were injected into one-half of the reactor that was still partially intact. A number of fires started, which contributed to more radioactive materials being released into the atmosphere. Immediate Aftermath of the Accident Chernobyl Nuclear Power Plant workers who operated the other functioning reactors, via Chernobyl Galleryįragments and hot graphite were thrown out from fuel channels and the reactor. A steam explosion occurred due to increased heat and steam production, and a second explosion followed seconds later. As operators continued to try and maintain power and steam pressure, they decided to lessen the amount of water needed to cool the reactor. This compromised the condition of the reactor even further. In an effort to maintain constant power, operators removed most of the control rods. However, only a handful of rods were used during the test compared to the minimum 30 rods required for safe operations. Control rods are used to help keep the reactor controlled. Plant operators attempted to increase the power level to a stabilized condition. Side of the Chernobyl Nuclear Power Plant that received the least amount of damage from the Unit 4 reactor explosion, via International Atomic Energy Agency As a result, it creates unstable conditions for the reactor and makes it vulnerable to sporadic power surges. When power levels are very low, it causes the positive void coefficient to become dominant. This process causes fuel temperatures also to increase. The RBMK reactor has a positive void coefficient, which means that steam production increases when power is increased, or water flow is decreased.

The power was reduced significantly below the level it should have been to stabilize the reactor’s condition prior to shutdown. However, the test was performed when the reactor was in an unstable condition. On April 25, 1986, a test was conducted during a routine maintenance shutdown to see if the reactor could produce electrical power for emergency equipment in the event that the station lost power. Plans for additional reactors were in place when the disaster occurred.

RBMK reactor Units 1 and 2 were constructed in the 1970s, and Units 3 and 4 were completed by 1983. The plant was stationed in present-day northern Ukraine, about 130 kilometers north of Kyiv and about 20 kilometers south of the Belarus border. RBMK is a Soviet-designed boiling light water reactor that uses uranium dioxide fuel. It consisted of four RBMK reactors, which could generate up to 1,000 megawatts of electric power per reactor. The Chernobyl Nuclear Power Plant was constructed in the late 1970s and early ‘80s. What Caused the Chernobyl Disaster? Aerial view of the destruction of the Chernobyl Unit 4 reactor courtesy of IAEA, 1986, via Britannica

Nuclear fission chernobyl