The Chernobyl The Chernobyl DisasterDisasterKatherine CulpKatherine Culp

Erin MeyerErin Meyer

http://mt.sopris.net/mpc/military/v/reactor.chernobyl.jpg

The IronyThe Irony

““This accident [Three Mile This accident [Three Mile Island] could only happen in a Island] could only happen in a capitalistic society where they capitalistic society where they put profits ahead of safety.”put profits ahead of safety.”

Professor Alexandrov, Professor Alexandrov, president of the Soviet president of the Soviet Academy of SciencesAcademy of Sciences

““Good Evening Comrades. Good Evening Comrades. All of you know that there has All of you know that there has been a incredible misfortune been a incredible misfortune – the accident at the – the accident at the Chernobyl nuclear plant. It Chernobyl nuclear plant. It has painfully affected the has painfully affected the Soviet people and shocked Soviet people and shocked the international community. the international community. For the first time, we confront For the first time, we confront the real force of nuclear the real force of nuclear energy, out of control.”energy, out of control.”

Soviet President Mikhail Soviet President Mikhail GorbachevGorbachev

Background: How a Nuclear Background: How a Nuclear Reactor WorksReactor Works

Uranium-235 can easily undergo induced Uranium-235 can easily undergo induced nuclear fission; free neutron + U-235 nuclear fission; free neutron + U-235 fission fission

Plutonium-239 can also be usedPlutonium-239 can also be used Reactor operates at critical state – one neutron Reactor operates at critical state – one neutron

ejected from each fission ejected from each fission another fission another fission Enriched uranium pellets arranged in long rodsEnriched uranium pellets arranged in long rods Bundle of rods submerged in coolant (water)Bundle of rods submerged in coolant (water) Bundle must be at supercritical stateBundle must be at supercritical state

Nuclear ReactorsNuclear Reactors

Supercritical state – if left alone, uranium Supercritical state – if left alone, uranium bundles would overheat and meltbundles would overheat and melt

Control rods – control rate of reactionControl rods – control rate of reaction Made of neutron-absorbing materialMade of neutron-absorbing material Can be raised or lowered into bundleCan be raised or lowered into bundle Raising Raising more heat generated more heat generated Lowering Lowering less heat less heat Completely lowering Completely lowering shut down reaction shut down reaction

Nuclear Reactors…Nuclear Reactors…

Bundle – heats water to form steamBundle – heats water to form steam Steam drives a steam turbineSteam drives a steam turbine Turbine spins a generator to produce Turbine spins a generator to produce

powerpower Containment vessel – prevents leakage Containment vessel – prevents leakage

of radioactive materialof radioactive material

RBMK Reactor – RBMK Reactor – Reactor Reactor Bolshoy Moshchnosty Bolshoy Moshchnosty KanalnyKanalny

http://classroom.psu.ac.th/users/ssmarn/pplant/Nuclear/NPP8_files/image002.gif

RBMK ReactorsRBMK Reactors

Only in RussiaOnly in Russia Produce power Produce power andand plutonium for military use plutonium for military use Design FlawsDesign Flaws

In order to remove the fuel rods for reprocessing In order to remove the fuel rods for reprocessing and obtaining plutonium, a crane is needed. and obtaining plutonium, a crane is needed. However, this makes the reactor too tall for a However, this makes the reactor too tall for a containment shell, which would keep radioactive containment shell, which would keep radioactive material from spreading in case of an accident.material from spreading in case of an accident.

Carbon moderator used instead of water. Carbon Carbon moderator used instead of water. Carbon moderators have a tendency to catch fire. moderators have a tendency to catch fire. Moderators are used to slow down rapid neutrons. Moderators are used to slow down rapid neutrons.

Positive Void CoefficientPositive Void Coefficient

Positive void coefficient – if the water in the reactor boils, Positive void coefficient – if the water in the reactor boils, steam bubbles are produced. In other reactors, excess steam bubbles are produced. In other reactors, excess steam pockets reduce nuclear activity and slow down the steam pockets reduce nuclear activity and slow down the nuclear reaction. But in RBMK reactors, the nuclear nuclear reaction. But in RBMK reactors, the nuclear reaction speeds up.reaction speeds up.

With a positive coefficient, a reactor is unstable at low power With a positive coefficient, a reactor is unstable at low power and is susceptible to a rapid power surge that is and is susceptible to a rapid power surge that is uncontrollable.uncontrollable.

In reactors with positive void coefficients, the moderator and In reactors with positive void coefficients, the moderator and coolant are in separate circuits or are different materials. coolant are in separate circuits or are different materials. However, RBMK reactors have no modifications to prevent However, RBMK reactors have no modifications to prevent the rapid, uncontrollable power surge that can be produced the rapid, uncontrollable power surge that can be produced by a positive void coefficient. by a positive void coefficient.

There are 13 RBMK reactors in the world still operating There are 13 RBMK reactors in the world still operating today.today.

Construction FlawsConstruction Flaws

Gross deviations were present in the construction of Gross deviations were present in the construction of the RBMK reactors at the Chernobyl plant.the RBMK reactors at the Chernobyl plant.

The foundation was not poured properly, so there were The foundation was not poured properly, so there were gaps in the foundation which could allow for leakage.gaps in the foundation which could allow for leakage.

Roof placement did not conform to design Roof placement did not conform to design specifications.specifications.

There was also damage to the waterproofing, which There was also damage to the waterproofing, which could allow for radioactive contamination of could allow for radioactive contamination of groundwater. The damage was backfilled instead of groundwater. The damage was backfilled instead of repaired.repaired.

An ExperimentAn Experiment

Reactor 4 was shut down for routine maintenance, and Reactor 4 was shut down for routine maintenance, and workers decided to run a test to determine if, during a workers decided to run a test to determine if, during a shutdown, enough electrical power could operate the shutdown, enough electrical power could operate the emergency equipment and core cooling pumps until emergency equipment and core cooling pumps until the diesel supply returned.the diesel supply returned.

Communication between group in charge of test and Communication between group in charge of test and group operating the nuclear reactor broke down. group operating the nuclear reactor broke down.

The emergency core cooling system was turned off; The emergency core cooling system was turned off; reactor operated at ½ power.reactor operated at ½ power.

The reactor stabilized at 1,000 MW, but operator error The reactor stabilized at 1,000 MW, but operator error caused the power to drop to 30 MW, a power at which caused the power to drop to 30 MW, a power at which the positive void coefficient can be a problem.the positive void coefficient can be a problem.

April 26, 1986April 26, 1986

Operators stabilized the system by withdrawing almost all the control Operators stabilized the system by withdrawing almost all the control rods. A minimum of 30 control rods is required; only 6-8 were left in rods. A minimum of 30 control rods is required; only 6-8 were left in place. If a power surge were to take place, operators would only have place. If a power surge were to take place, operators would only have 20 seconds to lower the rods and to shut down the reactor20 seconds to lower the rods and to shut down the reactor

Reactor became extremely unstable; operators had to make Reactor became extremely unstable; operators had to make adjustments every few seconds in order to keep the power constant.adjustments every few seconds in order to keep the power constant.

Operators decided to reduce the flow of water so that they could Operators decided to reduce the flow of water so that they could maintain the steam pressure. Turbine slowed maintain the steam pressure. Turbine slowed pumps not providing pumps not providing as much cooling for the reactor.as much cooling for the reactor.

More steam was created in the cooling channels More steam was created in the cooling channels power surge power surge about 100 times the normal power.about 100 times the normal power.

Power surge Power surge steam explosion which blew off the top off of the steam explosion which blew off the top off of the reactor. A second explosion took place a few seconds later; its origin reactor. A second explosion took place a few seconds later; its origin is not understood. is not understood.

Carbon moderator caught on fire; burned for nine days.Carbon moderator caught on fire; burned for nine days.

Initial Release of Initial Release of RadiationRadiation

When Reactor 4 went supercritical and When Reactor 4 went supercritical and exploded there was a ‘mechanical discharge of exploded there was a ‘mechanical discharge of dispersed radioactive fuel’, meaning that a dispersed radioactive fuel’, meaning that a plume of radioactive elements was released plume of radioactive elements was released into the atmosphere. This release was made into the atmosphere. This release was made up of isotopes that closely corresponded to the up of isotopes that closely corresponded to the fission products of spent fuel, including fission products of spent fuel, including 89,9089,90S, S, 131131I, and I, and 134,137134,137Cs, which made up the largest Cs, which made up the largest part of the initial emissions.part of the initial emissions.

The Days After the The Days After the AccidentAccident

From April 26From April 26thth to May 1 to May 1stst the rate of radioactive the rate of radioactive element release decreased because the core element release decreased because the core was covered with boron, lead, and sand in an was covered with boron, lead, and sand in an attempt to extinguish the fire that had begun attempt to extinguish the fire that had begun during the explosion.during the explosion.

This covering of the core, however, led to This covering of the core, however, led to temperatures in the core increasing and to temperatures in the core increasing and to release of more radiation in the form of release of more radiation in the form of 131131I. I. Estimates indicate that 50% of the core’s Estimates indicate that 50% of the core’s 131131I I was released.was released.

Soviet DisclosureSoviet Disclosure

The Soviets did not initially inform other nations The Soviets did not initially inform other nations of the disaster. The first indication European of the disaster. The first indication European nations had that a large-scale nuclear disaster nations had that a large-scale nuclear disaster had taken place was when nuclear plants in had taken place was when nuclear plants in Scandinavia began to register unusually high Scandinavia began to register unusually high levels of background radiation. The Soviets levels of background radiation. The Soviets denied all knowledge about the accident for denied all knowledge about the accident for several days. Full disclosure was not made several days. Full disclosure was not made until August of 1986until August of 1986

Soviet EvacuationSoviet Evacuation

The Soviet authorities did not evacuate The Soviet authorities did not evacuate the villages that surrounded Chernobyl the villages that surrounded Chernobyl until April 27. At that time they also until April 27. At that time they also provided iodine supplements for the provided iodine supplements for the evacuated residents. These evacuated residents. These supplements are supposed to help supplements are supposed to help prevent thyroid cancer by filling the prevent thyroid cancer by filling the thyroid with nonradioactive iodine so it thyroid with nonradioactive iodine so it doesn’t take up the radioactive forms.doesn’t take up the radioactive forms.

Soviet Response to Soviet Response to ChernobylChernobyl

The Soviet authorities sent in cleanup crews to The Soviet authorities sent in cleanup crews to supplement the workers already in Chernobyl. supplement the workers already in Chernobyl. Of those who were sent in to contain the fires Of those who were sent in to contain the fires and radiation damage, 29 died from intense and radiation damage, 29 died from intense ββ burns. There were also reports of 237 cases of burns. There were also reports of 237 cases of acute radiation sickness in the surrounding acute radiation sickness in the surrounding areas. Later research has questioned these areas. Later research has questioned these numbers, and there is some evidence that the numbers, and there is some evidence that the Soviets grossly underestimated the number of Soviets grossly underestimated the number of people made ill by the explosion and the people made ill by the explosion and the subsequent release of radioactive isotopes.subsequent release of radioactive isotopes.

Effects on the WorldEffects on the World

Chernobyl released radiation high into the Chernobyl released radiation high into the atmosphere, where it eventually was carried atmosphere, where it eventually was carried across Europe. The amount of radioactive across Europe. The amount of radioactive elements varied country by country, according elements varied country by country, according to their proximity to the Ukraine and also to their proximity to the Ukraine and also meteorological patterns. Countries that meteorological patterns. Countries that received a lot of rainfall in the days after the received a lot of rainfall in the days after the explosion tended to have higher levels of explosion tended to have higher levels of radiation due to the elements being sent out in radiation due to the elements being sent out in ‘fine aerosol form’ that was best carried by a ‘fine aerosol form’ that was best carried by a liquid medium. liquid medium.

Long-term effectsLong-term effects

Using risk models, researchers have Using risk models, researchers have estimated that the risk of developing estimated that the risk of developing cancer is doubled in those who were cancer is doubled in those who were within a thirty-mile radius of Chernobyl. within a thirty-mile radius of Chernobyl.

The modeled risks for those in Europe The modeled risks for those in Europe are considered statistically insignificant.are considered statistically insignificant.

Health EffectsHealth Effects

Researchers in 1996 indicated that, out of 235 villagers Researchers in 1996 indicated that, out of 235 villagers in the area of Chernobyl at the time of the explosion, in the area of Chernobyl at the time of the explosion, 35 had died of cancer. Many survivors suffer from 35 had died of cancer. Many survivors suffer from possibly radiation-influenced conditions such as goiter possibly radiation-influenced conditions such as goiter and diabetes.and diabetes.

A Russian Health Ministry report from the same time A Russian Health Ministry report from the same time indicates that half of the children in the areas irradiated indicates that half of the children in the areas irradiated by the fallout show signs of radiation sickness, by the fallout show signs of radiation sickness, including anemia, kidney failure, and lymph gland including anemia, kidney failure, and lymph gland inflammation.inflammation.

A Ukrainian biologist’s study indicates that 8500 of A Ukrainian biologist’s study indicates that 8500 of those who went in to clean up the radiation hot spots those who went in to clean up the radiation hot spots had died by the mid 1990s.had died by the mid 1990s.

The Chernobyl LegacyThe Chernobyl Legacy

After covering Reactor 4 with a cement After covering Reactor 4 with a cement sarcophagus that was intended to seal up the sarcophagus that was intended to seal up the radioactive elements, the Soviets continued to radioactive elements, the Soviets continued to operate the other reactors at Chernobyl.operate the other reactors at Chernobyl.

By the mid-’90s the sarcophagus was By the mid-’90s the sarcophagus was crumbling and international workers had to go crumbling and international workers had to go into Chernobyl and reinforce it.into Chernobyl and reinforce it.

The last reactor was shut down in late 2000.The last reactor was shut down in late 2000. People are still not allowed to live in an People are still not allowed to live in an

eighteen mile radius from Chernobyl.eighteen mile radius from Chernobyl.

SourcesSources

Anspaugh, Lynn R., et al. “The Global Impact of the Chernobyl Reactor Accident.” Anspaugh, Lynn R., et al. “The Global Impact of the Chernobyl Reactor Accident.” Science, Science, 242(Dec., 1988), 1513-1519.242(Dec., 1988), 1513-1519.

ApSimon, Helen, et. al. “Analysis of the Dispersal and Deposition of Radionuclides from ApSimon, Helen, et. al. “Analysis of the Dispersal and Deposition of Radionuclides from Chernobyl Across Europe.” Chernobyl Across Europe.” Proceedings of the Royal Society of LondonProceedings of the Royal Society of London . 425(Oct, . 425(Oct, 1989), 365-4051989), 365-405

Brain, Marshall. “How Nuclear Power Works.” Brain, Marshall. “How Nuclear Power Works.” http://science.howstuffworks.com/nuclear-power.htmhttp://science.howstuffworks.com/nuclear-power.htm

““Chernobyl: Assessment of Radiological and Health Impact.” Nuclear Energy Chernobyl: Assessment of Radiological and Health Impact.” Nuclear Energy Agency. http://www.nea.fr/html/rp/chernobyl/c01.htmlAgency. http://www.nea.fr/html/rp/chernobyl/c01.html

““Chernobyl Nuclear Disaster.” http://www.chernobyl.co.ukChernobyl Nuclear Disaster.” http://www.chernobyl.co.uk Dahlburg, John-Thor. “Study Finds Chernobyl Radiation Worse than Originally Dahlburg, John-Thor. “Study Finds Chernobyl Radiation Worse than Originally

Reported.” Reported.” Los Angeles TimesLos Angeles Times. April 14, 1992, pg. 2. April 14, 1992, pg. 2 ““Fire near Chernobyl reported out.” CNN.com, April 1996. Fire near Chernobyl reported out.” CNN.com, April 1996.

http://www.cnn.com/WORLD/9604/23/chernobyl.htmhttp://www.cnn.com/WORLD/9604/23/chernobyl.htm McCarthy, John. “Chernobyl.” McCarthy, John. “Chernobyl.”

http://www-formal.stanford.edu/imc/progress/chernobyl.htmlhttp://www-formal.stanford.edu/imc/progress/chernobyl.html ““The RMBK Reactor” World Nuclear Association. The RMBK Reactor” World Nuclear Association.

http://www.world-nuclear.org/info/inf31.htmhttp://www.world-nuclear.org/info/inf31.htm Wilson, Richard. “A Visit to Chernobyl.” Wilson, Richard. “A Visit to Chernobyl.” ScienceScience, 236(June, 1987), 1636-1640., 236(June, 1987), 1636-1640.