April 26, 1986 started out like any other day in the city of Prypiat (also spelled Pripyat), Ukraine (at the time under the USSR). People went to their jobs and children went to school, but before the day was over, the people of the city would be exposed to the worse catastrophe in the history of nuclear power plants. Yet, they didn’t even know what happened until hours later they begin to suffer from severe headaches, uncontrollable coughing and vomiting and had a metallic taste in their mouths. The following day the city of Prypiat was evacuated and a day after that, the Soviet Union announced there was an accident at the Chernobyl Nuclear Plant.
The Accident at the Chernobyl Nuclear Power Plant
At 1:23 a.m. on that fateful day in April, a sudden output surge of power in reactor number 4 led to the rupture of the reactor vessel and subsequently a series of explosions and massive fires. The day before, on the 25th of April, the reactor crew started preparations for testing new voltage regulator designs. The operators went through a series of actions, including disabling the automatic shutdown mechanisms. By the time the operators attempted to shut down the reactor, it was in an extremely unstable condition. A design flaw of the control rods caused a dramatic surge of power when they were being inserted into the reactor.
The extreme hot fuel interacted with the cooling water which led to fuel fragmentation combined with rapid steam production and pressure increase. The design of the reactor could not compensate for the damage to the fuel assemblies which resulted in destruction of the reactor. The increased pressure caused the cover plate of the reactor to partially detach which ruptured the fuel channels and jammed the control rods which where only about halfway down.
The intense steam generation spread throughout the whole core which caused a steam explosion and released fission products into the atmosphere. A couple of seconds later, a second explosion pushed out hot graphite and fragments from the fuel channels. An estimated quarter of the 1200 tons of graphite in the reactor was ejected and the fuel became incandescent; starting numerous fires which then caused the release of radioactivity into the environment.Credit: Photo courtesy of Jason Minshull
Immediately After the Chernobyl Disaster
Two operators were killed during the explosion, one immediately and the other soon afterwards at the hospital. Three minutes after the initial explosion the fire alarm was raised and two minutes later local firefighters arrived. At 1:32 a.m. Soviet fire fighter, Col. Leonid Telyatnikov was summoned to the nuclear power plant. He was the shift commander at the plant and as soon as he approached the plant, he knew it was no ordinary fire.
Telyatnikov led his crew into the area of the fire despite their radiation sensors freezing at the highest possible level, indicating the radiation levels were higher than they had been in Hiroshima after it was bombed. Other than their uniforms and gas masks, the fire fighters didn’t have extra protection to shield them. The fires were mostly localized by shortly before 5 a.m. and just after 6:30 a.m. all the fires except one contained inside the reactor 4 were extinguished. But the damage had been done; in a huge, far-reaching, long-standing way.
The radiation level in the worst areas of the reactor building were estimated at 5.6 roentgens per second (R/s) which is equivalent to 20,000 per hour; a lethal dose is 500 roentgens over five hours. Inaccurate low readings, the dismissal of a new dosimeter reading, and the ignoring of the debris lying around the building led the crew chief, Alexander Akimov and his crew to remain in the reactor building until morning as they attempted to pump water into the reactor.
Of the approximately 600 people who worked at the nuclear plant and including the about 30 fire fighters from local fire stations as well as stations from Prypiat (two miles away) and Kiev (50 miles away), 134 received high doses of radiation and suffered acute radiation sickness. Over the next four months, 28 of those died, among them six fire fighters, Akimov and most of his crew.
An estimated half of the iodine-131 and caesium-137 and all of the xenon gas along with five percent of the remaining radioactive material in the number 4 reactor was released during the accident. While most of the material landed close to the plant as dust and debris, some of the lighter radioactive material was carried by the wind over Ukraine, Russia, Belarus, the European parts of Turkey, Moldova, Romania, Bulgaria, Greece, Austria, Hungary, Czechoslovakia, Denmark, Norway, Lithuania, Poland, Estonia, Italy, France, Finland, Sweden, Yugoslavia, Germany, Switzerland, Ireland, Corsica, Canada, and the United Kingdom. It was estimated 60 percent of the fallout ended up over Belarus.Credit: Photo courtesy of the CIA
The Ensuing Days After the Chernobyl Disaster
The Soviet government initially downplayed the disaster. On the 26th, the same day as the accident, a state commission was set up to investigate the accident. It was headed by Valery Legasov and when he arrived at Chernobyl that evening, he was faced with two deaths and 52 in the hospital. By the following day, Legasov’s commission acknowledged the reactor’s destruction and ordered the evacuation of Prypiat. The afternoon of the 27th, the evacuation of Prypiat began—over 24 hours after the accident.
The official evacuation announcement instructed the residents of Prypiat to take their documents, a certain amount of food and some vital personal belongings. They were assured it was a temporary situation and the houses would be guarded by the police during their absence. They were informed senior executives of the city’s public and industrial facilities had made a list of employees who were to stay in Prypiat to maintain the facilities. At 2 p.m., buses were to take the residents out of the area for the short-term evacuation. By 3 p.m. 53,000 people were evacuated for what was supposed to be three days to various villages of the Kiev region. By May a total of about 116,000 people were evacuated from the area of a 19 mile radius of the plant.
The Soviet government continued to keep the accident secret, not informing other countries of the possible risk factors from the accident. On the 28th, two days after the accident, technicians at the Forsmark Nuclear Plant in Sweden were alarmed by signals of high levels of radiation in the area. They searched their plant for any leaks and finding none, they lined up all of their plant workers and tested them with a Geiger counter. The clothing of the workers read significantly higher than normal levels of radiation. They tested the grounds around their plant and the plants and soil indicated five times the normal amount of radioactive emissions.
Credit: Photo by Nick Rush-Cooper; licensed under CCA-SA 3.0 unportedThe Soviet Government could no longer hide the accident at Chernobyl. The general population of USSR were informed of the accident at Chernobyl and at the same time, ABC televised the news in the United States. The Soviets instituted an exclusion zone of about 19 miles surrounding the nuclear plant, known as the "zone of alienation" or the Exclusion Zone.. They now had a huge clean-up to undertake; not only the still burning reactor, but the surrounding grounds.
The Clean-up of the Nuclear Plant
The fire contained in reactor 4 continued to burn until May 10 and there were concerns of a steam explosion underneath the reactor because of the melting core and the bubbler pool underneath the reactor. The pool needed to be drained and could be done by opening its sluice gates. Three volunteers in diving suits entered the radioactive water and were able to find the valve and open the gates. All three emerged in apparent good condition, but later suffered radiation sickness and died. By May 8, the basement was completely drained of 20,000 metric tons of highly radioactive water.
The removal of the bubbler pool reduced the likelihood of a meltdown producing a steam explosion unless the liquid core reached the water table below the reactor. It was decided to freeze the ground beneath the reactor. Starting on May 4, drilling equipment injected liquid nitrogen into the ground. After a short time, the plan was abandoned and instead, the basement was filled with concrete.
The most radioactive of the debris around the plant was shoveled into the destroyed reactor; much of it by liquidaCredit: Photo by Elena Filatovators wearing heavy protective gear. Helicopters had covered the reactor with sand bags, lead, and boric acid. The liquidators were only able to work on the rooftops of the surrounding buildings for no longer than 40 seconds at a time due to the debris giving off high radiation.
Concern about the reactor exploding again, it was decided to build a new containment structure to prevent any further radioactive materials. By December 1986, 250,000 construction workers erected a large concrete sarcophagus to seal off the reactor. The workers reached their lifetime limits of radiation and a unique “clean-up medal was given to each. During the construction, scientists entered the reactor to locate and contain nuclear fuel to prevent another explosion, exposing themselves to high levels of radiation. They collected cold fuel rods, but the core continued to emanate heat. In December they discovered an immense mass, weighing hundreds of tons and composed of glass, sand and nuclear fuel. They called it “the Elephant Foot.” The concrete beneath the reactor was very hot and breached by solidified lava and unknown crystalline forms. At that point, they concluded the reactor was no longer at risk for another explosion.
Modern-Day Condition of Chernobyl
Soviet scientists' reports indicated 28,000 square kilometers (10,800 miles) were contaminated by caesium-137 to levels greater than185 kBq per square meter (a unit of measurement of radioactivity, equal to one disintegration per second). About 10,500 square kilometers (4,000 square miles) had a caesium-137 level greater than 555 kBq per square meter. Over a million people resided in those areas. The data was confirmed by the International Chernobyl Project.
After 1990, an additional 220,000 people were relocated from areas of Belarus, Ukraine and Russia. Many of the personal items are still inside the homes in Prypiat. Many of the vehicles the liquidators used are still parked in a field in the Chernobyl area. The sarcophagus around the reactor is decaying and therefore being reinforced with a new one surrounding the old. The reactor still contains about 200 tons of radioactive material. Reactors 1, 2, and 3 were decommissioned in 2000.
The Exclusion Zone has redefined its borders a few times, adding sub-zones related to radioactivity levels, but has maintained at least the 19 miles surrounCredit: Photo by Elena Filatovading the Chernobyl nuclear plant. Approximately 200 people (mostly women) continue to live within the zone, refusing to evacuate the area despite the danger. About 3,000 people work inside the Zone. Most do not live inside the Zone, but work shifts which are strictly regulated in regards to health issues and pensions. Employees are monitored for internal bio-accumulation of radioactive elements.
Brief visits to the Exclusion Zone are possible for the public by arranged guided tours from Kiev. Some evacuated residents of Chernobyl, Prypiat and smaller villages make an annual visit to their former homes. The Zone is also accessible, with permission, for scientists, journalists and other interested parties. The popularity of the site grew when Prypiat was featured in a couple of movies. Trespassers became a problem to the point, patrols were added to secure the area.
Long-lasting Effects of the Disaster
There is much debate as to the continuing effect on the flora and fauna of the contaminated areas as well as the wildlife. A forest near the facility was bulldozed and the wood buried. The soil continues to exude significant radiation. Fires stir up the radioactive elements in the ground and re-release them into the air. Animals and insects in the contaminated areas experienced deformities and mutations. There has also been an increase in the zone of some species, theorized to flourish because of the lack of human interference.
The long-term effect on the people who lived or still live in the contaminated areas is controversial. Most of the people were exposed to low levels of radiation and a causal link to radiation for their health issues is difficult to confirm without doubt. Studies are hampered by funding, willinCredit: Photo by Elena Filatovag participation and politics.
There are still concerns today about contamination of the soil with strontium-90 and caesium-137. Both elements have half-lives of about 30 years. The top soil carries the highest levels of caesium-137 which is absorbed by plants and insects, which results in the caesium-137 entering the local food supply. Decades later, restrictions still apply regarding the production, transportation and consumption of food contaminated by the fallout from the Chernobyl plant. It will take thousands of years for the ground around the Chernobyl Nuclear Power Plant to be considered fully safe.
The copyright of the article Decades Later Chernobyl Disaster Still a Problem is owned by Cheryl Weldon and permission to republish in print or online must be granted by the author in writing.