IB DP Physics: SL复习笔记8.1.6 Safety Issues in Nuclear Power

Safety Measures for Workers

• 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