High level waste

High level waste (HLW) is a type of nuclear waste that arises from the use of uranium fuel in a nuclear reactor and nuclear weapons processing. It contains the fission products and transuranic elements generated in the reactor core. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear electricity generation.

High level waste is very radioactive and, therefore, requires special shielding during handling and transport. It also needs cooling, because it generates quite a lot of heat because of the high radioactivity level.

A typical large nuclear reactor produces 25-30 tons of spent fuel per year. If the fuel were reprocessed and vitrified, the waste would be only about 3 cubic meters per year.

It is generally accepted that the final waste will be disposed of in a Deep geological repository, and many countries have developed plans for such a site including the US, Japan, and France.

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Definitions

High level waste is defined as:

Spent (used) reactor fuel.

• Spent nuclear fuel is used fuel from a reactor that is no longer efficient in creating electricity, because its fission process has slowed due to a build-up of reaction poisons. However, it is still thermally hot, highly radioactive, and potentially harmful.

Waste materials from reprocessing.

• Materials for nuclear weapons are acquired by reprocessing spent nuclear fuel from breeder reactors. Reprocessing is a method of chemically treating spent fuel to separate out uranium and plutonium. The byproduct of reprocessing is a highly radioactive sludge residue.

Disposing of high-level wastes

High-level radioactive waste is stored temporarily in spent fuel pools and in dry cask storage facilities.

In 1997, in the 20 countries which account for most of the world's nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilised. With annual additions of about 12,000 tonnes, issues for final disposal are not urgent.

See also

• Radioactive waste
• low level waste
• transuranic waste
• spent nuclear fuel
• mixed waste

References

Fentiman, Audeen W. and James H. Saling. Radioactive Waste Management. New York: Taylor & Francis, 2002. Second ed.

Large, John H Risks and Hazards arising the Transportation of Irradiated Fuel and Nuclear Materials in the United Kingdom R3144-A1, March 2006 [1]