Radiation and Nuclear Accidents




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Chapter 7 : Radiation and Nuclear Accidents



Radiation arrow_upward


  • Radiation is nothing more than the emission of energy waves through:
    • Space
    • Physical objects
  • Usually these energy waves are:
    • Particulate
    • Electromagnetic radiations
  •  Energy Waves are classified into:
    • Radio waves,
    • Infrared waves,
    • Visible light,
    • Ultraviolet waves,
    • X-ray,
    • Gamma rays and,
    • Cosmic rays.

    Nuclear Radiations arrow_upward


  • Nuclear Radiation often refers to the ionizing radiation from nuclear decay.
  • Ionizing radiation is called so because it is capable of ionizing the things it hits.
  •  


    Ionizing Radiation arrow_upward


  • Ionizing Radiation includes both electromagnetic (X and gamma rays) and particulate radiation.
  • Particles are
    • Alpha,       
    • Beta, 
    • Neutrons.
  • Ionizing radiation has high frequency and short wave length.
  • All nuclear radiations are ionizing radiations, but the reverse is not true.
  • Example:
    • X-rays are included among ionizing radiations, but they are not nuclear radiations since they do not originate from atomic nuclei.

    Important Nuclear Radiations arrow_upward


  • The important nuclear radiations are:
    • Alpha Particles,
    • Beta Particles,
    • Gamma rays, 
    • Neutron Particles.

    Alpha Particles arrow_upward


  • A helium nuclei consisting of two neutron and two protons.
  • Emitted from radioisotopes such as plutonium, uranium.
  • Unable to penetrate skin.
  • Very destructive once it gets into the body through:
    • Inhalation
    • Ingestion
  • An internal hazard like tissue damage occurs if swallowed.
  • Protective Measures:
    • Alpha particles do not penetrate the dead layer of skin.
    • Can be stopped by a thin layer of paper or clothing.

    Beta Particles arrow_upward


  • Negatively charged.
  • Beta particles are high-energy electrons emitted from a nucleus.
  • Able to penetrate skin.
  • Can produce superficial skin burns.
  • Emitted by several radioisotopes (e.g. Cobalt 160).
  • Protective Measures:
    • Protective clothing.
    • Example: Universal precautions
    • Layer of less than an inch of a substance.
    • Example: Plastic, aluminum

    Neutron Particles arrow_upward


  • Uncharged.
  • Able to penetrate deeply.
  • Hazard inside nuclear reactors.
  • Neutrons can be very destructive to human tissue.
  • Able to travel
    • Many feet in concrete and,
    • Thousands of feet in air.
  • Neutrons are not likely to be encountered except in the initial seconds of a nuclear criticality event.
  • Protective Measures:
    • Thick layers of materials with lots of hydrogen in them (like water or concrete) are used.
    • Protective clothing provides no shielding from neutron radiation.

    Gamma Rays and X-Rays (Photons) arrow_upward


  • Gamma rays and X-rays are able to travel:
    • Many feet in air
    • Many inches in human tissue
  • Because, they don’t have mass or charge, they penetrate very deeply.
  • Gamma and X radiation differ by
    • Source.
    • Gamma rays come from the nucleus.
    •  X-rays come from the electron orbits.
  • They readily penetrate most materials.
  • Protective Measures:
    • Thick layers of dense materials like lead are needed to shield against gamma radiation.
    • Protective clothing provides little shielding from gamma and X radiation.
    • But will prevent contamination of the skin with the gamma emitting radioactive material.
    • A person exposed to X-rays or gamma rays does not become radioactive.

    Penetration abilities of Different Types of Radiations arrow_upward



    Detecting Radiation arrow_upward


  • Radiation cannot be seen, heard, tasted or smelled.
    • Damage is caused by the energy from radioactive material.
    • The longer the exposure, the worse the outcome will be.
  • But, it can be easily measured if you have the right equipment.

  • Radiation Detectors arrow_upward


  • There are two kinds of radiation monitors used for medical purposes:
    • Survey Meters
    • Personal monitors

    Radiation Detectors


    Contamination arrow_upward


  • Contact with radioactive materials that can be spread to others.
    • People
    • Properties
  • Inhaled, ingested or transferred from surface to surface.

  • Nuclear Accidents arrow_upward


  • One of the scariest things about nuclear power is when something goes wrong and an accident occurs.
  • Radiation is released into the environment and people get hurt.

  • Causes of Nuclear Accidents arrow_upward


  • There are a number of causes of such events, ranging from equipment failure and human error to loss of coolant or spillage in an accident in transportation.
  • A major nuclear accident happens when the core of a nuclear reactor is damaged by a meltdown or partial meltdown.
  • There are other types of nuclear accidents, including loss of radiological materials intended for medical use.
  • Reactor designers try to anticipate every possible fault route and ensure the design is robust enough.
  • Risks such as earthquakes and aircraft crashes are assessed.
  • Avoidance of accidents does require well thought out operating procedures, and well trained staff who can work out what is happening in an unusual event, combined with reliable instruments.

  • US, Three Mile Island, 1979 arrow_upward


  • The United States' most disastrous
  • nuclear accident took place at the Three Mile Island Plant near Harrisburg, Penn., the state's capitol.
  • It all began with a simple plumbing break down.
  • A small valve opened to relieve pressure in the reactor, but it malfunctioned and failed to close.
  • This caused cooling water to drain, and the core began to overheat.
  • The machines monitoring conditions inside the nuclear core provided false information.
    • So plant operators shut down the very emergency water that would have cooled the nuclear core and solved the problem.
  • The core began to overheat and reached 4,300 degrees Fahrenheit.
  • The water nearly reached the fuel rods, which would have caused a full melt-down of the core.
  • Three Mile Island had a profound impact on the public's attitude toward nuclear energy.
  • In the 30 years since Three Mile Island, not a single nuclear power plant has been approved for development.

  • Soviet Union (now Ukraine), Chernobyl, 1986 arrow_upward


  • The Chernobyl nuclear accident is widely regarded as the worst accident in the history of nuclear power.
    • An experiment was to take place in the reactor.
  • As a result, normal safety guidelines were disregarded, and the accident occurred.
  • The reactor's fuel elements ruptured and there was a violent explosion.
  • The fuel rods melted after reaching a temperature over 3,600 degrees Fahrenheit.
  • The graphite covering the reactor then got ignited and burned for over a week, spewing huge amounts of radiation into the environment.
  • About 200,000 people had to be permanently relocated after the disaster.
  • IAEA reported in 2005 that 56 deaths could be linked directly to the accident.
  • Forty-seven of those were plant workers and nine were children who died of thyroid cancer.
  • The report went on to estimate that up to 4,000 people may die from long-term diseases related to the accident.

  • Japan, Tsunami and Subsequent Nuclear Reactor Explosion, 2011 arrow_upward


  • On March 11 at 2:46pm JST a massive 9.0-magnitude earthquake occurred near the northeastern coast of Japan, creating extremely destructive tsunami waves which hit Japan just minutes after the earthquake, and triggering evacuations and warnings across the Pacific Ocean.
  • Radiation levels at the Tokaimura nuclear fuel-processing plant in north-east Japan are much higher than normal.


  • Thank You from Kimavi arrow_upward


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