Waste Management
All human activities create waste that needs to be managed carefully, however radioactive waste is a form of waste that is given special consideration and is managed under strict rules and guidelines. There has been, and continues to be considerable research to investigate methods of reducing and minimising the risk of contamination and damage from radioactive waste.
Radioactive waste, like any waste, needs to be managed to protect people and the environment. Radioactive waste results from the uses of radioactive material, for example, medical, industrial, agricultural, and nuclear energy generation. Such waste is classified as either low-level, intermediate-level, or high-level, depending on the amount and type of radioactive material in it. These definitions are agreed upon by the international organisations that actively formulate the methods for managing radioactive wastes.
|
Low-level radioactive waste occurs as protective clothing, tools, equipment rags, filters, etc., that mostly contain short-lived radioactivity. Although it does not need to be shielded, it needs to be disposed of in a different manner than when disposing of every-day garbage. Low-level waste is usually compacted or burnt and placed in shallow landfill sites. Intermediate-level radioactive wastes are resins, chemical sludges, metal fuel cladding, and materials from nuclear electricity plants. The spent fuel from Lucas Height's (Sydney) research reactor is also classified as intermediate-level waste. It is generally short-lived, but usually needs to be shielded. Intermediate-level waste can be solidified in concrete and put into a waste repository. High-level radioactive waste comes from spent fuel from the reactor. It must be shielded and cooled. |
Each level of waste needs different types of management. It is the disposal of the high-level radioactive material that causes the most concern. It generates heat, as well as radiation. The material has a long half-life and has to be continually cooled.
The storage and disposal of the high-level radioactive waste requires careful management. However, the cooling and isolation is very straight forward. High-level waste from the world's nuclear power plants has been stored this way for more than 40 years.
About 30 grams of radioactive waste is produced per 8000 kWh of electricity generated. To produce the same amount of electricity using high-quality black coal, 8 tonnes of carbon dioxide (which at standard atmospheric temperature and pressure would fill three full-sized Olympic pools) is produced.
Once uranium has been used to generate electricity, it becomes 'spent fuel'. This is the waste product of nuclear reactors and can be dealt with in several ways. As this spent fuel is highly radioactive, it cannot be, and definitely is not, simply dumped. It is often temporarily stored in special ponds that allow the fuel to 'cool down' and decrease its radioactivity. It cannot cause significant damage in these storage ponds. An important factor to address in storing different types of radioactive waste is how long they present a danger to society.
Although the spent fuel can be stored in these special ponds for fairly long periods of time, eventually the fuel will need to be either reprocessed, or disposed of. Reprocessing involves separating the remaining uranium and plutonium from the waste products in the spent fuel, by cutting up the fuel rods and dissolving them in acid. The recovered uranium is then returned to the beginning of the nuclear fuel cycle, and the plutonium is mixed with this to produce more fuel. After reprocessing, the highly radioactive waste can be heated to produce a powder, a process called calcining. This powder is mixed with glass to encapsulate (or lock-in) the waste, a process called vitrification. The liquid glass is then poured into stainless steel canisters for storage - and to this day, that is where the nuclear cycle ends.
| Disposal of the stored spent fuel
and vitrified waste is predicted to take place in about 2010 when there
are sufficient quantities to justify the operation of a commercial
disposal site. Extensive research and testing have shown that the waste
can be tightly sealed and buried deep underground, in stable rock
formations, such as granite. Once the waste has been buried for about
1,000 years, its radioactivity will have reduced to about that of
naturally occurring uranium ore.
Waste from uranium mining is handled differently in underground mining and in situ leaching. |
Greater technical detail can be found on this topic by searching through the listed briefing papers and education resources at www.uic.com.au.
|
The Uranium SA Website is supported by the South Australian Chamber of Mines and Energy | |
| © 2001 SA Chamber of Mines and Energy. | |
|
Information, artwork, text, data and pictures on this web site may be reproduced freely with due acknowledgment of SA Chamber of Mines and Energy. It would be appreciated if you could please let us know what material you are using. All feedback is most welcome. Please contact: |
|
| uraniumsa@resourcessa.org.au | www.uraniumsa.org |
