Sunday, March 27, 2011

Nuclear Reactors and Chernobyl

Demonstration of a Nuclear Reactor (4)
Nuclear Reactors: (4)
  • Nuclear reactors contain and control chain reactions to produce energy (usually heat)
  •  Heavy neutrons and a small neutron sources are placed in the reactor vessel (tank)
  •  When the atom splits, it releases neutrons that causes another atom to split, creating a chain reaction
  • When an atom splits, it releases large amounts of energy in the form of heat
  • Next, the heat is carried out of the reactor by a coolant, water, and the coolant heats up and continues to a turbine to spin a generator or drive shaft
  •  There are several types of nuclear reactors because they include different fuels, coolants, fuel cycles, sand purposes
  •  Some examples are: pressurized water reactor, sodium cooled fast reactor, high temperature gas cooled reactor, and boiling water reactor

The different parts: (4)
  •  Core- contains all of the nuclear fuel and generates all of the heat
  •  Coolant- can be water, heavy- water, liquid sodium, helium, or something that will perform the function to pass through the core, transferring heat from the fuel to a turbine
  •  Turbine- transfers the heat from the coolant to electricity
  •  Containment- structure that breaks apart the reactor and the environment (Chernobyl did not have a containment)
  • Cooling towers- where the power plant releases the excess heat that cannot be converted to energy

The Nuclear Core (4)
  •    Fuel pins

o   Smallest unit of the reactor
o   Made of uranium oxide and surrounded by a zirconium clad to keep fission products from dodging the coolant

  • Fuel assembly

o   Bundles of fuel pins
o   How fuel is put in and taken out
o   Keeps the pins close, but not touching so the coolant touch all of the fuel pins

  •  Full core

o   Made up of hundreds of assemblies
o   The assemblies vary in types of fuel and height

History of Chernobyl:


  •  Chernobyl is a nuclear power plant in the wooded marshlands of the northern Ukraine (3)
  • The fourth reactor of the power plant began working in 1983 (3)
  • Pripyat was a small town built near Chernobyl to house its workers and their families (3)
  • April 25- 1986 at 1 a.m.: Chernobyl’s technicians shut down reactor four for maintenance and to run a test to see if during a power outage the turbines could produce enough energy to keep the cooling system running until backup generators started (3)
  •  The test was delayed because the nearby town, Kiev wanted their power
  • The test began again on April 26 at 1 a.m., but the reactor’s power dropped suddenly
  • The reactor went out of control and exploded at 1:23 a.m. (3)
  •  The explosion created a fire that lasted for ten days and spread radioactive fallout over tens of thousands of square miles (1)
  • The Soviet Union tried to keep the explosion a secret, but on April 28, the Swedish Forsmark nuclear power plant in Stockholm registered very high radiation levels near their plant (3)
  • The Soviet Union denied any information about a nuclear disaster to plants around Europe until 9 p.m. on April 28 when they proclaimed one of the reactors had been damaged (3)

What went wrong at Chernobyl?
  •  While running the test, the operators turned off many of the safety systems which could have fixed the low power the reactor was experiencing, but instead the reactor when out of control and exploded (3)
  • The operators were too careless about the procedures of safety (2)

What has been done to remedy the situation?
  •  In order to put out the fires, the Soviet Union poured water, sand, lead, and nitrogen on them for about two weeks until they were all put out (3)
  • They sealed contaminated topsoil in barrels (3)
  • Chernobyl Nuclear Power Plant is located in a fenced in area called the Exclusion Zone (1)
  • Around reactor four there is a 24- story concrete and steel encasement, a sarcophagus, to contain the radioactive remnants (1)
  • The sarcophagus is shaky and might collapse, so a plan for a new one to slide over the old encasement to seal in the remaining nuclear fuel is being planned, but it will cost about two billion dollars (1)
  • The new sarcophagus is estimated to be finished in 2013 (3)

Lasting effects of the disaster:
  • The burning reactor created a cloud that spread various radioactive materials, especially iodine and caesim radionuclides (2)
  •  Radioactive iodine- 131 disintegrated during the first few weeks of the accident because of its short half life of 8 days (2)
  •  Caesium- 137 can still be measured in soils and some of the foods in parts of Europe because of its long half life of 30 years (2)
  • The largest deposits of radionuclides are found in Belarus, the Russian Federation, and Ukraine (2)
  •  31 people died right after the explosion and thousands are dying from the long term effects of radiation (3)
  • An environmental organization predicts more than 100,000 people have already died as the consequence of the disaster (1)
  •  It is predicted that 4,000 people will suffer a cancer- related illness because of the accident (1)
  • Quarter of a million people moved away permanently from their homes (1)
  •  Pripyat, the town that housed 50,000 plant worker is now a ghost town (1)
  •  In the abandoned villages, collapsed houses are disappearing under overgrowth (1)
  • There is now a greater search for alternative energy sources other than nuclear power (1)
  •  Since the Soviet had lied about knowing of the explosion of the reactor, there is a extensive distrust of official information and the mistaken acknowledgment of many ill health conditions to radiation exposure (2)

Fun Facts:
  •  About 400 elderly people returned to their homes, ignoring the radiation levels (1)
  • Chernobyl accident is equivalent to 500 nuclear bombs used in Hiroshima in 1945. (6)
  • The releases contaminated an estimated 17 million people to some degree. (6)
  • 143,000 people have been evacuated from contaminated areas of Ukraine (6)
  • 600,000 people took part in liquidating effects of the disaster, 100,000 of which already died or are now handicapped (6)
  • Cases of leucosis and thyroid cancer exceed average by 2 and 5 times correspondingly among the Chernobyl victims. (6)
  • There are 1.8 million people residing on the territories of Ukraine, Russia, and Belarus, which are still defined as contaminated (6)
  • For the 14 years since the disaster 300,000 died in Ukraine alone from the radiation sickness (6)

Chernobyl vs. Fukushima (5)
Chernobyl (9)

Fukushima (8)

  •  Radiation lingered over a large area and a fallout cloud was created
  •  People evacuated their homes as soon as they heard the radiation was dangerous
  • The people who were exposed to the radiation gained different illnesses like cancer
  • Both disasters spread and affected many people

  • Other countries like America are working with Japan, while in Chernobyl the Soviet Union denied the explosion at first to other countries in Europe and did not receive help
  •  Chernobyl occurred because the operators were careless, while the nuclear power plant in Japan, Fukushima, exploded because of a few design flaws and the earthquake and tsunami that hit it
  • Chernobyl experienced more premature deaths than Fukushima
  • Fukushima's reactors are safer than Chernobyl's reactors because they were surrounded by steel and water

Should we be worried?
  • No, radiation should not reach America
  •  There are people watching the radiation levels constantly
  •  Only issue would be if the supplies from Japan contained radiation, but the radiation level would be low enough that it will not affect humans
  • To be aware of, information on Fukushima is still being researched, and many people are worried that Japan is sending misleading information

Work Cited