Background:
The Chernobyl Nuclear Power Plant, in total, was 8.5 square miles of 22 square kilometers, located in, Pripyat, Ukraine. Construction of the nuclear power plant began August 15th, 1972, and consequently halted after the events on April 26th,1986. Of the four nuclear reactors that were fully functional in Chernobyl, the reactors served about 8,400,000 people in Belarus, Ukraine, and Russia. The Soviet Nuclear Power Programme, who headed the building of the Chernobyl Nuclear Power Plant, was based mainly on two types of reactors, the WWER, a pressurized light-water reactor, and the RBMK, a graphite moderated light-water reactor.
Timeline of Events:
On April 25, 1986, at 01:00 the reactor was running at full power with normal operation. Steam power was directed to both turbines of the power generators. Slowly the operators began to reduce power for the test. The purpose of the test was to observe the dynamics of the RMBK reactor with limited power flow. At 14:00, under the normal procedures of the test, the reactor would have been reduced to 30% power, but the Soviet electricity authorities refused to allow this because of an apparent need for electricity elsewhere, so the reactor remained at 50% power for another 9 hours. On April 26, 1986, at 01:19, shutdown signals blocked from steam-drum separators. The operator blocks automatic shutdown due to low water level and the loss of bother turbines because of a fear that a shutdown would abort the test. Soon after the automatic shutdown was disabled, at 01:21, the caps to fuel channels on charge face seen jumping in their sockets and at 01:21:50 the pressure fails in the steam drums. Once the crew realized there was a problem, they tried to act immediately because at 01:23:40, the crew tried emergency reinsertion of all control rods. As the temperature of the water became too high as bubbles reached the main circulation pumps. The coolant started boiling in the reactor, and the reactor power slowly increased. The lead worker presses the AZ-5 button, class-5 emergency. The control rods, according to the synchro indicators, seized at a depth of between 2 and 2.5 meters instead of inserting to their full depth of 7 meters. The reactor was now making rumbling noises. Suddenly, there was confusion – the reactor control panel indicated no water flow and failure of pumps. April 26, 1986, 01:23:44, there is an explosion. The reactor reaches 120x its full power. All the radioactive fuel disintegrates and steam brakes all of the pressure tubes leading to the explosion. The 1000-ton lid above the fuel elements is lifted by the explosion and the release of radiation starts. Burning debris flies into the air and lands on the roof of Chernobyl Unit Air filled with dust, the power went out. The fire was so huge in Reactor’s 3 and 4 that they needed so many extra hands to stop the release of radiation before it spread too far. At 02:15, the Pripyat Department of the Ministry of Home Affairs calls a crisis meeting and it is decided to roadblock cars from leaving or entering the town as thousands of police arrive unaware of the radiation leak. Soon after that, 37 fire brigades, with a total of 186 firefighters, have now been called in. All fires extinguished with the exception of the fire contained inside Reactor 4. Although there is no single version on what exactly triggered the explosion, wrongdoing by the stations’ staff and failure to follow safety regulations together with the reactor’s defects are most often tipped as the key cause.
Effects of the nuclear explosion:
Nuclear explosions produce air-blast effects similar to those produced by conventional explosives. The shock wave can directly injure humans by rupturing eardrums or lungs or by hurling people at high speed, but most casualties occur because of collapsing structures and flying debris. Unlike conventional explosions, a single nuclear explosion can generate an intense pulse of thermal radiation that can start fires and burn skin over large areas. In some cases, the fires ignited by the explosion can coalesce into a firestorm, preventing the escape of survivors. Though difficult to predict accurately, it is expected that thermal effects from a nuclear explosion would be the cause of significant casualties. Nuclear detonations release large amounts of neutron and gamma radiation. Relative to other effects, initial radiation is an important cause of casualties only for low-yield explosions (less than 10 kilotons). When a nuclear detonation occurs close to the ground surface, soil mixes with the highly radioactive fission products from the weapon. The debris is carried by the wind and falls back to Earth over a period of minutes to hours. Of the six nuclear reactors of Chernobyl’s Nuclear Plant: Reactor number 1 was shut down in 1996, Reactor number 2 shut down in 1991, Reactor number 3 was shut down in 2000, Reactor number 4 was permanently destroyed in Chernobyl Disaster in 1986, Reactor number 5 was never completed, and Reactor number 6 was never completed. Two people died immediately as a result of the blast at the Chernobyl nuclear plant in Ukraine – then part of the Soviet Union – on 26 April 1986. Another 29 died in hospital during the next few days. The longer-term impact of the radiation, however, has proved harder to quantify. The radiation dose absorbed by a person is measured using the conventional unit rad or the SI unit gray (Gy). The biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert (Sv).
The radioactive materials released by the accident had many immediate harmful effects on plants and animals living within 20 to 30 km of the Chernobyl power plant at the time of the accident. However, there are no reports of any such radiation-induced effects in plants and animals outside this area, referred to as the Exclusion Zone. Each plant and animal responded differently to the accident depending on the dose of radiation received and sensitivity to radiation. Overall, in plants and animals, when high doses were sustained at relatively close distances from the reactor, there was an increase in mortality and a decrease in reproduction. During the first few years after the accident, plants and animals of the Exclusion Zone showed many genetic effects of radiation. Still today there are reports of anomalies in plants and animals both in the Exclusion Zone and beyond.
Because radioactive cesium is continuously taken up through water and passed on by organisms in forest ecosystems, the animals and vegetation in affected forests and mountains are particularly contaminated. Forest food products such as mushrooms, berries, and game contain the highest recorded levels of cesium-137.After the accident, the deposition of radioactive iodine contaminated agricultural plants, grazing animals, and thus the milk produced in parts of Belarus, Russia, Ukraine and some other parts of Europe. This direct deposition on plants was of most concern during the first two months after the accident since radioactive iodine decays quickly. After this early phase of deposition, an increasingly important concern was plant contamination through absorption of radioactive materials, such as cesium and strontium, from the soil through their roots.
Damage caused by the Chernobyl disaster is estimated at some $235 billion. However, the overall amount of money that Belarus and the international community invested into the recovery amounts to just 8 percent of the total damage. The Economic damage of the Chernobyl accident is estimated at $235 billion for 30 years on after the explosion, making up 32 national budgets as of 1985. The Chernobyl disaster vastly damaged the agricultural sector of the Belarusian economy, which is worth over $700 million annually. Due to radioactive fallout, Belarus lost one-fifth of all agricultural lands.
Remediation Work:
There are two main goals of remediation work for Chernobyl: the provision of treatment facilities for radioactive waste and interim storage for spent nuclear fuel, to support safe decommissioning of reactor Units 1-3 and the Shelter Implementation Plan (SIP), designed to transform the existing arrangements at the destroyed reactor Unit 4 to a stable and environmentally safe state. So far, the UN and EU has been able to provide infrastructure facilities for the construction site, including refurbished utility provision, new road and rail connections and a large changing facility with medical and radiation screening provision, introduce a number of programs to ensure adequate worker safety and protection, notably systematic medical care and screening programs and a training program to help develop a new safety culture, and install a new nuclear, radiation and seismic Integrated Monitoring System and improve site access control and physical protection systems.