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In 1970, the city of Pripyat was founded.
- Named after the nearby Pripyat River, Pripyat was founded on 4 February 1970 in northern Ukraine which was then part of the Soviet Union.
- It was built to house the employees of the Chernobyl Nuclear Power Plants located 4km away and became the ninth nuclear city in the Soviet Union.
- Pripyat was officially proclaimed a city in 1979 and had a population of roughly 49,400 prior to being evacuated in the Chernobyl disaster.
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Construction of Chernobyl Nuclear Power Plant began
- On August 15th 1972, the construction of Chernobyl Nuclear Power Plant (ChNPP) began with the purpose to provide electricity for Ukraine.
- ChNPP consisted of 4 RBMK-1000 reactors, each capable of producing 1,000 megawatts (MW) of electric power (3,200 MW of thermal power), and the four together produced about 10% of Ukraine's electricity.
- The completion of the first reactor in 1977 was followed by reactor No. 2 in 1978, No. 3 in 1981, and No. 4 in 1983.
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RBMK - High-Power Channel Reactor
- RBMK (Reaktor Bolshoy Moshchnosty Kanalny), aka the light water graphite reactor, is a water-cooled reactor with individual fuel channels and using graphite as its moderator.
- As with a boiling water reactor (BWR), water boils in the fuel channels (at about 6.9 MPa) and steam is separated above them in a single circuit.
- However, the RBMK is an unusual reactor design which had several shortcomings, failures in safety tests, and was involved in the 1986 Chernobyl disaster.
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FAILURES IN SAFETY TESTS
- An initial test in 1982 indicated that the excitation voltage of the turbine-generator was insufficient;
- The electrical system was modified, and the test was repeated in 1984 but again proved unsuccessful.
- In 1985, the test was conducted a third time but also yielded no results due to a problem with the recording equipment.
- The test was run again in 1986 and was scheduled to take place during a controlled power-down of reactor No. 4, which was preparatory to a planned maintenance outage.
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Reactor No.1 partial meltdown
- A partial core meltdown occurred in reactor No.1 due to a faulty cooling valve remaining closed following maintenance.
- Once the reactor came online, the uranium in the tank overheated and ruptured. The extent of the damage was comparatively minor, and no one was killed during the accident.
- Due to the negligence of the operators the accident was not noticed until several hours later, resulting in significant release of radiation in the form of fragments of radioactive isotopes.
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Unit 4 of Chernobyl Nuclear Power Plant was completed
- The construction of Unit 4 at Chernobyl is completed, and the plant becomes operational on the 20th.
- This news was reported by the media on 22 December was a festive day for workers in the energy industry.
- In the Soviet Union it was customary for all sections of public employment to have their own special day when they receive public acclaim for their work and are given extra bonuses.
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RADIOACTIVE FALLOUT
- **The explosions killed two plant workers - the first of several workers who died within hours of the accident.
- 1 engineer – Valery Khodemchuk. He was the first official victim of the disaster whose body was never to be found.**
- Next several days, as emergency crews tried to contain the fires and radiation leaks, the death toll climbed as workers succumbed to acute radiation sickness.
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Release of Radiation
- Most of the radiation released from the accident was from fission products iodine-131, cesium-134 and cesium-137.
- Iodine-131 has a short half-life of 8 days, but it is rapidly ingested through the air and tends to localize in the Thyroid gland.
- Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years) and are a concern for years after their release into the environment.
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More Details about the Chernobyl Explosion
- The excess steam was created by the reduction of the cooling water, which caused steam to build up in the cooling pipes, lead to enormous power surge that the operators could not shut down.
- The fire spread from reactor #4 to adjacent reactors. Toxic fumes and dust were carried by the blowing wind.
- Causing large quantities of radioactive materials and airborne isotopes to disperse in the atmosphere and surrounding land.
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REACTOR #4 CATASTROPHE - CHERNOBYL DISASTER
- At 1:23 am on April 26, the Chernobyl disaster occurred at reactor No. 4, caused by a catastrophic power increase resulted in core explosions and open-air booming fires.
- During a routine maintenance check, operators were planning to test the electrical systems when they turned off vital control rods which going against the safety regulations. This caused the reactor to reach dangerously unstable and low-power levels.
- It first was caused by an excess of steam.
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Evacuation
About 36 hours after the accident occured (on April 27), Evacuations of Pripyat commenced. By that time, many residents were already complaining about vomiting, headaches, and other signs of radiation sickness
- The 43,000 resident evacuation took 3.5 hours using 1,200 buses from Kiev.
- By May 14, officials closed off an 30km area around the plant, evacuating another 116,000 residents.
- In the next few years, 220,000 more residents were advised to move to less contaminated areas. -
Valery Legasov commits suicide
- Two years after explosion Valery Legasov the director of Chernobyl committed suicide In the Institute of Nuclear Energy was where the RBMK reactors were designed.
- He was also chairman of the scientific team sent to Chernobyl after the accident.
- A day before he killed himself he left his records in which he wrote about his anger about the safety of nuclear energy in the Soviet Union. Legasov also wrote that the accident was bound to happen.
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HEALTH EFFECTS
- 28 workers of Chernobyl died in 4 months after the accident including some heroic workers/firefighters who knew they were exposing themselves to deadly levels of radiation to secure the facility from further radiation leaks.
- In the first 3 days there were 299 patients hospitalised with clear forms of radiation sickness (acute radiation syndrome)
- Between 1991 and 2015, as many as 20,000 cases of thyroid cancer cases were diagnosed in patients who were under the age of 18 in 1986.
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ENVIRONMENTAL IMPACTS
- Chernobyl put 400 times more radiation into the Earth than did the atomic bombing of Hiroshima at the end of World war II.
- Shortly after the radiation leaks, the trees in the woodlands surrounding the power plant were killed by high levels of radiation. This region came to be known as the "Red Forest" because the dead trees turned into a bright ginger color.
- Surrounding Chernobyl land - "exclusion zone" restricted to everyone.
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1991 REACTOR #2 TURBINE FIRED
- On 11 October 1991, a fire broke out in the turbine hall of reactor No. 2. The fire began in reactor No. 2's fourth turbine, while the turbine was being idled for repairs.
- A faulty switch caused a surge of current to the generator, igniting insulating material on some electrical wiring.
- This subsequently led to hydrogen, used as a coolant in the synchronous generator, being leaked which caused the fire and collapse of the reactor.
- Reactor No. 2 was permanently shut down after that.
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New Safe Confinement
- The damaged #4 reactor was hastily sealed in a concrete sarcophagus to contain the remaining radiation.
- An enclosure called the New Safe Confinement structure began construction in late 2006 to completely enclose reactor #4 and its surrounding sarcophagus for at least the next 100 years.
- The Chernobyl nuclear plant was still in operation to meet the power needs until the other three reactors #2 - #1 and #3 was respectively shut down in 1991, 1996, and 2000. -
CHERNOBYL TODAY
Today, the region, including within the exclusion zone, is filled with a variety of wildlife that have thrived without interference from humans.
- Thriving populations of wolves, deer, lynx, beaver, eagles, bears and other animals have been documented in the dense woodlands that now surround the silent power plant.
- The area has recovered to some extent but is still far from returning to normal. But in the areas just outside the exclusion zone, people are beginning to resettle.