AQA A Level Physics

Revision Notes

8.4.7 Safety Aspects of Nuclear Reactors

Safety Aspects of Nuclear Reactors

Nuclear Fuel

  • The fuel used in nuclear reactors is called enriched uranium
    • This is U-238 enriched with U-235 as U-235 is the isotope that undergoes fission
    • The U-238 isotope absorbs fission neutrons which helps to control the rate of fission reactions
  • Several measures are in place to reduce the worker’s exposure to radiation
    • The fuel rods are handled remotely ie. by machines
    • The nuclear reactor is surrounded by a very thick lead or concrete shielding, which ensures radiation does not escape
    • In an emergency, the control rods are fully lowered into the reactor core to stop fission reactions by absorbing all the free neutrons in the core, this is known as an emergency shut-down

Nuclear Waste

  • There are three main types of nuclear waste:
    • Low level
    • Intermediate level
    • High level

 

  • Low-level waste
    • This is waste such as clothing, gloves and tools which may be lightly contaminated
    • This type of waste will be radioactive for a few years, so must be encased in concrete and stored a few metres underground until it can be disposed of with regular waste

 

  • Intermediate-level waste
    • This is everything between daily used items and the fuel rods themselves
    • Usually, this is the waste produced when a nuclear power station is decommissioned and taken apart
    • This waste will have a longer half-life than the low-level waste, so must be encased in cement in steel drums and stored securely underground

 

  • High-level waste
    • This waste comprises of the unusable fission products from the fission of uranium-235 or from spent fuel rods
    • This is by far the most dangerous type of waste as it will remain radioactive for thousands of years
    • As well as being highly radioactive, the spent fuel roads are extremely hot and must be handled and stored much more carefully than the other types of waste
  • How high-level waste is treated:
    • The waste is initially placed in cooling ponds of water close to the reactor for a number of years
    • Isotopes of plutonium and uranium are harvested to be used again
    • Waste is mixed with molten glass and made solid (this is known as vitrification)
    • Then it is encased in containers made from steel, lead, or concrete
    • This type of waste must be stored very deep underground

Risks & Benefits of Nuclear Power

  • Benefits
    • Nuclear power stations produce no polluting gases
    • They are highly reliable for the production of electricity
    • They require far less fuel as uranium provides far more energy per kg compared to coal and other fossil fuels
  • Risks
    • The production of radioactive waste is very dangerous and expensive to deal with
    • A nuclear meltdown, such as at Chernobyl, could have catastrophic consequences on the environment and to the people living in the surrounding area

Nuclear Energy in Society

  • Nuclear power can scare people if they do not understand it
  • It is dangerous if not handled properly, yet it is invisible which can be difficult for some people to comprehend
  • However, with increased education on nuclear energy, society can use this knowledge to inform their own decisions and opinions
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