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The Chernobyl Disaster
26 April 1986
A routine safety test on April 26, 1986, at the Chernobyl nuclear power station in Chernobyl, Ukraine (the former Soviet Union) was deemed so routine that the plant's director didn't even bother showing up. It quickly spiraled out of control, however, as an unexpected power surge and steam build-up led to a series of explosions that blew apart the reactor. The disaster was the product of a flawed Soviet reactor design coupled with serious mistakes made by the plant
operators. It was a direct consequence of Cold War isolation and the resulting lack of any safety culture. Workers on reactor unit 4 attempted a poorly designed experiment. Workers shut down the reactor's power-regulating system and its emergency safety systems, and they withdrew most of the control rods from its core while allowing the reactor to continue running at 7 percent power. These mistakes were compounded by others, and at 1:23 am the chain reaction in the core
went out of control. Several explosions triggered a large fireball and blew off the nearby steel and concrete lid of the reactor. This and the ensuing fire in the graphite reactor core released large amounts of radioactive material into the atmosphere, where it was carried great distances by air currents. The result was a partial meltdown of the reactor's core.
Do you remember the day that the Chernobyl disaster happened?What were you thinking as the disaster was happening?
Emergency crews responding to the accident used helicopters to pour 5000 tons of sand, clay, boron, dolomite and lead on the reactor's debris. The sand was to stop the fire and additional releases of radioactive material; the boron was to prevent additional nuclear reactions. A few weeks after the accident, the crews completely covered the damaged unit in a temporary concrete structure, called the "sarcophagus,' to limit further release of radioactive material. The Soviet government also cut down and buried about a square mile of pine forest near the plant to reduce radioactive contamination at and near the site. Chernobyl's three other reactors were subsequently restarted, but all eventually shut down for good, with the last reactor closing in 1999. On April 27, the 30,000 inhabitants of Pryp'yat began to be evacuated. A
cover-up was attempted, but on April 28, Swedish monitoring stations reported abnormally high levels of wind-transported radioactivity and pressed for an explanation. The Soviet government admitted there had been an accident at Chernobyl, thus setting off an international outcry over the dangers posed by the radioactive emissions.
By May 4th, both the heat and radioactivity leaking from the reactor core were being contained, at great risk to workers. Radioactive debris was buried at some 800 temporary sites, and later moved the year the highly radioactive reactor core was enclosed in a concrete-and-steel sarcophagus. (which was later deemed structurally unsound).After the accident, officials closed off the area within 18 miles of the plant, except for persons with official business at the plant and those people evaluating and dealing with the consequences of the accident and operating the undamaged reactors.
Why do you think the Soviets did not alert the surrounding countries of the disaster?
Why did they not evacuate the surrounding towns until a day later?
Immediate Impact of the Chernobyl AccidentThe accident caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation, and large quantities of radioactive substances were released into the air for about 10 days. Between 50 and 185 million curies or radionuclides (radioactive forms of chemical elements) escaped into the atmosphere - several times more radioactivity than that created by the atomic bombs dropped on Hiroshima and Nagasaki, Japan. This radioactivity was spread by the wind over Belarus, Russia and Ukraine and soon reached as far west as France and Italy. Millions of acres of forest and farmland were contaminated and although many thousands of people were evacuated, hundreds of thousands more remained in contaminated areas. Some sources state that two people were killed in the initial explosion, whereas others report that the figure was closer to 50. Dozens more contracted serious radiation sickness; some of these people later died.
The next task was cleaning up the radioactivity at the site so the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. About 200,000 people from all over the Soviet Union were involved in the recovery and clean-up during 1986 and 1987.
The effects of radiation exposure fall into two main classes: deterministic effects, where the effect is certain to occur under given conditions (e.g. individuals exposed to several grays over a short period of time will definitely suffer Acute Radiation Syndrome); and stochastic effects, where the effect may or may not occur (e.g. an increase in radiation exposure may or may not induce a cancer in a particular individual but if a sufficiently large population receive a radiation exposure above a certain level, an increase in the incidence of cancer may become detectable in that population). UNSCEAR, 2011.
Do you think the number of deaths could possibly be a number way higher than the actually number of reported deaths?
Health Effects from the AccidentThe Chernobyl accidents severe radiation effects killed 28 of the site's 600 workers in the first four months after the event. Another 106 workers received high enough doses to cause acute radiation sickness. Two workers died within hours of the reactor explosion from non-radiological causes. Another 200,000 clean-up workers in 1986 and 1987 received doses between 1 and 100 rem (the average annual radiation dose for a U.S. citizen is about 0.6 rem). Chernobyl cleanup activities eventually required 600,000 workers, although only a small fraction of these workers were exposed to elevated levels of radiation. Government agencies continue to monitor cleanup and recovery worker's health. A large increase in the incidence of thyroid cancer has occurred among people who were young children and adolescents at the time of the accident and lived in the most contaminated areas of Belarus, the Russian Federation and Ukraine. This was due to the high levels of radioactive iodine released from the Chernobyl reactor in the early days after the accident. Radioactive iodine was deposited in pastures eaten by cows who then concentrated it in their milk which was subsequently drunk by children. In Belarus, the Russian Federation and Ukraine, nearly 5,000 cases of thyroid cancer among children who were aged up to 18 years at the time of the accident have been reported.
Ionization radiation is also known to cause certain types of leukemia (a malignancy of blood cells). An elevated risk of leukemia was first found among the survivors of the atomic bombings in Japan some 2-5 years after the exposure. Recent investigations suggest a doubling of the incidence of leukemia among the most highly exposed Chernobyl liquidators. No such increase has been clearly demonstrated among children or adult residents in any of the contaminated areas. It is possible that a large proportion of the leukemia cases that could be linked to Chernobyl have already occurred, now that 30+ years have passed since the accident. Further studies are needed to clarify this. An increased number of cancer deaths can be expected during the lifetime of persons exposed to radiation
from the accident. Since it is currently impossible to determine which individual cancers were caused by radiation, the number of such deaths can only be estimated statistically using information and projections from the studies of atomic bomb survivors who received high radiation doses in a short time period, while Chernobyl caused low doses over a long time. This and other factors, such as
trying to estimate doses people received some time after the accident, as well as differences in lifestyle and nutrition, cause very large uncertainties when making projections about future cancer deaths. Chernobyl may have also caused cancers in Europe outside Belarus, the Russian Federation and Ukraine. However, the average dose to these populations is much lower so the relative increase in cancer deaths is expected to be much smaller. Predicted estimates are very uncertain and it is very unlikely that any increase in these countries will be detectable using national cancer statistics.
Do you think the percentage of cancer caused by the Chernobyl radiation is higher than scientists will be able to predict?
A large Russian study among emergency workers has suggested an increased risk of death from cardiovascular disease in highly exposed individuals. Also, the Chernobyl accident led to extensive relocation of people, loss of economic stability, and long term threats to health in current and future generations. Widespread feelings of worry and confusion, as well as a lack of physical and emotional well-being were commonplace. The dissolution of the Soviet Union soon after the Chernobyl accident, and the resultant instability in health care, added further to these reactions. High levels of stress, anxiety and medically unexplained physical symptoms continue to be reported
among those affected by the accident. The accident has had a serious impact on mental health and well-being in the general population. This has resulted in excessive health concerns or reckless behavior, such as the overuse of alcohol and tobacco, or the consumption of mushrooms, berries and game from areas still designated as having high levels of radioactive cesium.
Would you feel safe living around the contaminated area?Why do you think they returned, knowing the danger?
Locals Secretly ReturnDespite the warning signs and the legal implications of re-entering the zone, some residents decided to return. Known in local dialect as "Samosely," meaning self-settlers" they are a group of roughly 200 residents who live in the contaminated "ghost towns." The majority are elderly people who have lived in their homes since their childhood. When the population was evacuated, they either refused to leave or secretly resettled in the unprotected region. The average age of these illegal residents was 63 in 2007 and, in 2012 local governments unofficially granted permission to the elderly to continue living in the area, but demanded younger inhabitants to move out. This group lives in private households, they cultivate vegetable and fruit gardens, fish on the Pypyat river and gather mushrooms - in spite of widespread contamination. After failing to force the population out of the area, the government now supports locals in 11 surrounding villages. A truck passes through the area once a week handing out basic supplies including rice, flour and pasta to allow the Samosel's to survive.
Chernobyl TodayThe Chernobyl Unit 4 was enclosed in a large concrete shelter which was erected quickly (by October 1986) to allow continuing operation of the other reactors at the plant. However, the structure was neither strong nor durable. Major work was carried out in 1998 and 1999. About 200 tons of highly radioactive material remain within it, and this posesses an environmental hazard. In 2017, the New Safe Confinement (NSC) structure was completed. It had been built adjacent to the reactor and then moved into place on rails. It covers both unit 4 and the hastily-built 1986 structure. The hermetically sealed building allows engineers to remotely dismantle the 1986 structure that has shielded the remains of the reactor from the weather since the weeks after the accident. It will enable the eventual removal of the fuel-containing materials in the bottom of the reactor building. This is the most important step in eliminating nuclear hazard at the site - and then the real start of dismantling.
Animals Rule Chernobyl Three Decades after the Nuclear DisasterIt may seem strange that Chernobyl, and area known for the deadliest nuclear accident in history, could become a refuge for all kinds of animals - from moose, deer, elk, Przewalsk's horse, wild boar, beaver, and owls to more exotic species like brown bear, lynx, European bison, and wolves! Without people hunting them or ruining their habitat, the wildlife is thriving despite high levels of radiation. Radiation is bad for people and animals. Radioactive material enters the animals system through the food chain. The level of radionuclide contamination in an animal depend both on concentrations in its habitat and on the diet and behaviors of the animal. Radiation deposited by
fallout from Chernobyl has been measured as far away as Norway in reindeer, but it is patchily spread in the exclusion zone. Wolves, in particular, may get at least some protection from radiation because they have a big territory and move around a lot, even outside the zone into cleaner areas.
Animals Rule Chernobyl Three Decades after the Nuclear Disaster
The animals are radioactive because they eat radioactive food, so they may produce fewer young and bear mutated progeny. Even so, populations have grown. The damaging effects of radiation inside the zone may be less than the threat posed by humans outside of it. Not all animals fare well in the exclusion zone. Invertebrate populations (including bees,
butterflies, spiders, grasshoppers and dragonflies) in particular have diminished. This is likely because the animals lay eggs in the top layer of soil, which contains high levels of radioactivity. Radionuclides in water have settled into the sediment in lakes. Aquatic organisms are contaminated and face ongoing genetic instability. Affected species include frogs, fish, crustaceans, and insect larvae. While birds abound in the exclusion zone, they are examples of animals that
still face problems from radiation exposure. A study of barn swallows from 1991 to 2006 indicated birds in the exclusion zone displayed more abnormalities than birds from a control sample, including deformed beaks, albinistic feathers, bent tail feathers, and deformed air sacs. Birds in the exclusion zone had less reproductive success. Chernobyl birds often have smaller brains, malformed sperm and
cataracts. Not all of the animals around Chernobyl are entirely wild. There are around 900 stray dogs, mostly descended from those left behind when people evacuated the area. Veterinarians, radiation experts and volunteers from a group called the "Dogs of Chernobyl" capture the dogs, vaccinate them against diseases and tag them. The dogs offer a way to map radiation across the exclusion zone and studying the ongoing effects of the accident. The dogs are radioactive.
Engaging Questions!1. Would you have returned to your home after the Chernobyl disaster if it was in the affected zone?2. Do you think the radioactive area will ever fully recover?3. Would you go visit the abandoned town of Chernobyl on a tour?4. How safe would you feel restarting the three other nuclear reactors next to the destroyed one?5. What do you think they will do with all the nuclear waste that they recover from the reactor?6. How do you feel about using nuclear radioactivity for power?7. Do you think an incident will happen like this again?8. Do you remember the Three Mile Island nuclear disaster in 1978?
Curious Dragonfly LLCwww.curiousdragonfly.comTrina Terrell303.903.5319