WASTE

Emmaline Campbell

Radioactive Waste

Low-level waste• Low activity• Half-lives of

radioactive isotopes are short

• Includes: rubber gloves, paper towels, and protective clothing used in a radioactive location

High-level waste• High activity• Isotopes have long

half-lives, so waste will remain reactive for a long time

• Source: spent fuel rods or the reprocessing of spent nuclear fuel

Storage and disposal of nuclear waste : Low-level waste

• Discharge directly into sea so it dilutes (illegal in some countries)

• The decay produces heat, so better to store in big tanks of cooled water called ponds, where it can lose activity. Before it is discharged to the sea, it is filtered through an ion exchange resin, which removes strontium and caesium (radioactive elements).

• Other methods of disposal: keeping the waste in steel containers inside concrete-lined vaults.

Storage and disposal of nuclear waste : High-level waste

• During reprocessing of spent fuels, about 3% is high-level liquid waste that must be disposed of. Vitrification is the process that treats this waste by drying it in a furnace and feeding it into a melting pot together with a glass-making material. This molten material is poured into tubes, where it solidifies. Air circulates, keeping the tubes cool.

Storing and disposing of high-level waste, continued

• The problem is how to store this material for a long period of time, as it has high activity and a long half-life, so it will remain active for thousands of years.

• One solution is to encase it in concrete and bury it in a mine. The concern is that it will leach into the water supply somehow.