Radioactive Waste: Classificaction

Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment.

Thailand Institute of Nuclear Technology (TINT) low-level radioactive waste barrels.
Thailand Institute of Nuclear Technology (TINT) low-level radioactive waste barrels. Photo: ShinRyu Forgers

What is the classification of radioactive waste?

Classification of radioactive waste varies by country. The IAEA, which publishes the Radioactive Waste Safety Standards (RADWASS), also plays a significant role.[35] The proportion of various types of waste generated in the UK:
  • 94% – low-level waste (LLW)
  • ~6% – intermediate-level waste (ILW)
  • <1% – high-level waste (HLW)
Photo: Top layer is compacted hazmat suits, subsequent layers are irradiated soil and sediment all encased in concrete. This drum is Low Level Waste so there's a chance it's real. There's no way you could do this with intermediate or high level waste.
Top layer is compacted hazmat suits, subsequent layers are irradiated soil and sediment all encased in concrete. This drum is Low Level Waste so there's a chance it's real. There's no way you could do this with intermediate or high level waste.

Mill tailings

Uranium tailings are waste by-product materials left over from the rough processing of uranium-bearing ore. They are not significantly radioactive. Mill tailings are sometimes referred to as 11(e)2 wastes, from the section of the Atomic Energy Act of 1946 that defines them. Uranium mill tailings typically also contain chemically hazardous heavy metal such as lead and arsenic. Vast mounds of uranium mill tailings are left at many old mining sites, especially in Colorado, New Mexico, and Utah.

Removal of 1500 cubic yards of soil contaminated with extremely low levels of nuclear waste from the former Fort Greely Nuclear Power Plant. Fort Greely, Alaska.
Removal of 1500 cubic yards of soil contaminated with extremely low levels of nuclear waste from the former Fort Greely Nuclear Power Plant. Fort Greely, Alaska.

Although mill tailings are not very radioactive, they have long half-lives. Mill tailings often contain radium, thorium and trace amounts of uranium.

Low-level waste

Low-level waste (LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. Low-level wastes include paper, rags, tools, clothing, filters, and other materials which contain small amounts of mostly short-lived radioactivity. Materials that originate from any region of an Active Area are commonly designated as LLW as a precautionary measure even if there is only a remote possibility of being contaminated with radioactive materials

Intermediate-level waste

Intermediate-level waste (ILW) contains higher amounts of radioactivity compared to low-level waste. It generally requires shielding, but not cooling. Intermediate-level wastes includes resins, chemical sludge and metal nuclear fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen or mixed with silica sand and vitrified for disposal. As a general rule, short-lived waste (mainly non-fuel materials from reactors) is buried in shallow repositories, while long-lived waste (from fuel and fuel reprocessing) is deposited in geological repository.

One wagon of a nuclear waste flask train being hauled through Bristol Temple Meads railway station by Direct Rail Services Class 37 diesel locomotives 37612 and 37069 en-route from Hinkley Point Power Station to Sellafield.
Spent fuel flasks are transported by railway in the United Kingdom. Each flask is constructed of 14 in (360 mm) thick solid steel and weighs in excess of 50 t. (One wagon of a nuclear waste flask train being hauled through Bristol Temple Meads railway station by Direct Rail Services Class 37 diesel locomotives 37612 and 37069 en-route from Hinkley Point Power Station to Sellafield).

High-level waste

High-level waste (HLW) is produced by nuclear reactors and the reprocessing of nuclear fuel. The exact definition of HLW differs internationally. After a nuclear fuel rod serves one fuel cycle and is removed from the core, it is considered HLW. Spent fuel rods contain mostly uranium with fission products and transuranic elements generated in the reactor core. Spent fuel is highly radioactive and often hot.

Nuclear Waste Container coming out of Nevada Test Site on public roads, March 2010
Modern medium to high-level transport container for nuclear waste. Photo: Bill Ebbesen

The radioactive waste from spent fuel rods consists primarily of cesium-137 and strontium-90, but it may also include plutonium, which can be considered transuranic waste.

Half-lives of radioactive elements

The half-lives of these radioactive elements can differ quite extremely. Some elements, such as cesium-137 and strontium-90 have half-lives of approximately 30 years. Meanwhile, plutonium has a half-life that can stretch to as long as 24,000 years.

The current locations across the United States where nuclear waste is stored
The current locations across the United States where nuclear waste is stored

The amount of HLW worldwide is currently increasing by about 12,000 tonnes every year. A 1000-megawatt nuclear power plant produces about 27 t of spent nuclear fuel (unreprocessed) every year.

For comparison, the amount of ash produced by coal power plants in the United States alone is estimated at 130,000,000 t per year and fly ash is estimated to release 100 times more radiation than an equivalent nuclear power plant.

Anti-nuclear protest near nuclear waste disposal centre at Gorleben in northern Germany
Anti-nuclear protest near nuclear waste disposal centre at Gorleben in northern Germany. (Bündnis 90/Die Grünen protest against nuclear energy near nuclear waste disposal centre Gorleben in northern Germany where a trainload of treated waste arrived from France. The signs say, "Only the risk is certain. Atomic power? No, thanks.!")

In 2010, it was estimated that about 250,000 t of nuclear HLW were stored globally. This does not include amounts that have escaped into the environment from accidents or tests. Japan is estimated to hold 17,000 t of HLW in storage in 2015. As of 2019, the United States has over 90,000 t of HLW. HLW have been shipped to other countries to be stored or reprocessed and, in some cases, shipped back as active fuel.

The ongoing controversy over high-level radioactive waste disposal is a major constraint on the nuclear power’s global expansion. Most scientists agree that the main proposed long-term solution is deep geological burial, either in a mine or a deep borehole. As of 2019 no dedicated civilian high-level nuclear waste is operational as small amounts of HLW did not justify the investment before.

Diagram of an underground low-level radioactive waste disposal site
Diagram of an underground low-level radioactive waste disposal site. Nuclear Regulatory Commission from US - Low Level Waste Disposal

Transuranic waste

Transuranic waste (TRUW) as defined by U.S. regulations is, without regard to form or origin, waste that is contaminated with alpha-emitting transuranic radionuclides with half-lives greater than 20 years and concentrations greater than 100 nCi/g (3.7 MBq/kg), excluding high-level waste. Elements that have an atomic number greater than uranium are called transuranic (“beyond uranium”). Because of their long half-lives, TRUW is disposed of more cautiously than either low- or intermediate-level waste. In the United States, it arises mainly from nuclear weapons production, and consists of clothing, tools, rags, residues, debris, and other items contaminated with small amounts of radioactive elements (mainly plutonium).

Under U.S. law, transuranic waste is further categorized into “contact-handled” (CH) and “remote-handled” (RH) on the basis of the radiation dose rate measured at the surface of the waste container. CH TRUW has a surface dose rate not greater than 200 mrem per hour (2 mSv/h), whereas RH TRUW has a surface dose rate of 200 mrem/h (2 mSv/h) or greater. CH TRUW does not have the very high radioactivity of high-level waste, nor its high heat generation, but RH TRUW can be highly radioactive, with surface dose rates up to 1,000,000 mrem/h (10,000 mSv/h). The United States currently disposes of TRUW generated from military facilities at the Waste Isolation Pilot Plant (WIPP) in a deep salt formation in New Mexico.

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