Managing nuclear waste

There are three different classifications of radioactive waste: low, intermediate and high.

Low level waste emits low radiation levels and does not need much shielding, it includes items that have become contaminated with radioactive material or have become radioactive through exposure to neutron radiation. This waste typically consists of contaminated protective shoe covers and clothing, wiping rags, mops, filters, equipments and tools, medical tubes, swabs, injection needles and syringes.

Intermediate and high level waste require more shielding and safety processes to handle. Intermediate Level Solid Waste (ILSW) is generated chiefly from radiopharmaceutical production, and reactor operations. The spent fuel from ANSTO's research reactor is classified as intermediate-level waste. It is generally short-lived, but usually needs to be shielded. Intermediate-level waste can be solidified and put into a waste repository. Radioactivity gradually diminishes as radioactive elements decay into more stable elements, so waste gradually becomes less radioactive and safer to handle over time.

Most of Australia's current production of radioactive waste comes from ANSTO. Other sources include radioactive materials produced for medical, research and industrial applications. >There are relatively large amounts of waste in storage which arose from 'non-nuclear' activities, such as CSIRO research or the use of radium in luminous dials. See Amounts of Radioactive Waste in Australia.

Radioactive waste is handled according to its classification. Most of the solid radioactive waste produced by ANSTO is low-level waste. ANSTO produces some intermediate-level wastes, mainly from the production of molybdenum for nuclear medicine treatments. A small amount of intermediate-level waste will also arise from the reprocessing of ANSTO's spent nuclear fuel and both low and intermediate level waste will result from the decommissioning of the HIFAR research reactor over the next decade. Australia does not produce any high level waste.

What does Australia currently do with its radioactive waste?

The management of radioactive waste is governed by rigorous national and international standards. At ANSTO, low-level solid waste is segregated for long-term storage in earthquake-proof facilities. Low-level wastewater is collected, analysed and treated to reduce its radioactivity to internationally acceptable levels. The treated water is then discharged to sewer in accordance with a trade waste agreement with Sydney Water. Airborne discharges are trapped and treated. Intermediate solid waste is securely stored below ground in purpose-built facilities. Liquid waste is stored in shielded tanks before being processed into solid form for long-term storage.

Spent fuel from the HIFAR and OPAL nuclear research reactors at Lucas Heights is securely stored for several years before being sent overseas for processing or storage. The intermediate level waste resulting from reprocessing of HIFAR's fuel in France and Scotland, will be sent to Australia and stored in the proposed national radioactive waste facility. OPAL spent fuel will be sent to the USA for storage where it will remain. The USA does not reprocess fuel. Currently waste from other medical and industrial facilities are dealt with by the responsible state or territory government.

What do other countries do with their radioactive waste?

Other countries handle low-level and intermediate radioactive waste in much the same way as Australia does. Low-level waste is usually kept in near-surface storage, while intermediate waste is stored in purpose-built above-ground facilities.

Spent nuclear fuel rods are typically put into long-term storage in purpose-built ponds at reactor sites until activity has fallen off enough for reprocessing. This is where any remaining uranium or plutonium is separated and re-used as fuel, as part of a closed cycle. The remaining material can be safely and permanently immobilised using methods such as vitrification or synroc (synthetic rock).

How much radioactive waste does a nuclear power plant produce?

In countries with nuclear power, radioactive waste make up less than one per cent of total industrial toxic wastes.

A nuclear power plant generating 500 megawatts of electricity produces around 20 tonnes of toxic waste a year, and this figure is falling as nuclear reactors become more efficient. Treatment of nuclear waste can reduce the volume substantially. In comparison, a 500-megawatt coal-fired power station produces almost 320,000 tonnes of toxic waste each year, including 2.6 tonnes of uranium and 6.4 tonnes of radioactive thorium.

Future for waste management

Some countries are developing deep geological repositories for secure long-term storage of intermediate and high-level wastes. Finland, Sweden and the US have begun a site selection process.

Researchers are also developing high-temperature methods for reducing the volume of radioactive waste and 'partitioning and transmutation processes' for transforming the most active and long-lived components of radioactive waste into less hazardous materials.

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Nuclear Waste Disposal

As we near the end of the century, the disposal of nuclear waste is becoming a concern. Many nuclear power plants around the world are nearing the end of their operating lives. This is particularly true in the United States where most nuclear power plants are approaching the end of the operational time period allowed in their licenses. Locally the Ginna power plant, 20 miles northeast of Rochester, on Lake Ontario, is attempting to deal with these issues. The close of the cold war has left us with radioactive waste from decommissioned nuclear missiles.

The disposal of radioactive waste from nuclear power plants and nuclear missiles is as politically intense an issue as the plants and missiles themselves. Yet the three issues have remained curiously separate in spite of their close physical ties. Few debates on nuclear power or nuclear weapons discuss the problems of waste disposal should the power plant or missile be decommissioned. >Few debates on nuclear waste disposal discuss the opportunities to close nuclear power plants or get rid of nuclear weapons a disposal site would afford.

Nuclear waste can be generally classified a either "low level" radioactive waste or "high level" radioactive waste. Low level nuclear waste usually includes material used to handle the highly radioactive parts of nuclear reactors (i.e. cooling water pipes and radiation suits) and waste from medical procedures involving radioactive treatments or x-rays. Low level waste is comparatively easy to dispose of. The level of radioactivity and the half life of the radioactive isotopes in low level waste is relatively small. Storing the waste for a period of 10 to 50 years will allow most of the radioactive isotopes in low level waste to decay, at which point the waste can be disposed of as normal refuse.

High level radioactive waste is generally material from the core of the nuclear reactor or nuclear weapon. This waste includes uranium, plutonium, and other highly radioactive elements made during fission. Most of the radioactive isotopes in high level waste emit large amounts of radiation and have extremely long half-lives (some longer than 100,000 years) creating long time periods before the waste will settle to safe levels of radioactivity. This area will describe some of the methods being under consideration, for dealing with this, high level, waste. These include short term storage , long term storage, and transmutation.

source : http://www.history.rochester.edu/class/EZRA/

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