Radioactive Waste Management (DP IB Physics)

Safety Issues in Nuclear Power

Types of Radioactive 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

• High-level waste refers to 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 rods are extremely hot and must be handled and stored much more carefully than the other types of waste

• The issues with high-level waste are:

  • Within the fuel rods, nuclei of uranium-238 quickly decay into nuclei of plutonium-239

  • Plutonium-239 is classified as high-level radioactive waste

  • This is because its nuclei are extremely radioactive and have a very long half-life of 24 000 years

  • This presents a long-term risk of contamination

• The treatment of high-level waste is as follows:

  • 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

Depending on the activity of radioactive waste, it is buried in different ways

Advantages & Disadvantages of Nuclear Power

Advantages of using nuclear power:

• Climate change friendly:  Nuclear power stations produce no greenhouse gases

• High energy density:  Uranium provides far more energy per kg compared to coal and other fossil fuels

• Availability of fuel:  The reserves of fissionable materials are much higher compared to fossil fuel reserves

• High reliability & safety:  Despite some serious incidents in the past, nuclear power is now regarded as one of the safest and most reliable processes for the production of electricity

Disadvantages of using nuclear power:

• Hazardous waste products:  The production of radioactive waste is very dangerous and expensive to deal with and stays at hazardous levels of activity for a very long time (>1000s of years)

• Potential for catastrophic accidents:  A nuclear meltdown, such as at Chornobyl, could have catastrophic consequences on the environment and for the people living in the surrounding area

• Potential for misuse:  There is a danger of misuse of nuclear material and infrastructure in nuclear weapons and terrorist attacks

• Dangers with mining fuel:  There are many issues associated with mining uranium, from the people handling it to the detrimental effects it can have on the environment

Environmental Considerations

• Isotopes with long half-lives must not enter our water and food supplies

• Burial locations must be geologically stable, secure from attack, and designed for safety

• Space for such locations is limited

Safety Measures for Workers

• Several measures must be put in place to reduce the worker’s exposure to radiation

• The fuel rods are handled remotely i.e. by machines

• The nuclear reactor is surrounded by a very thick lead or concrete shielding to limit exposure to radiation

• 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 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