Radioactive Waste Management

Introduction | Radioactive Waste | Types of Radioactive Waste | Where Waste is Produced? | How Much Waste is Produced? | Treatment and Conditioning | Storage and Disposal | Interim Waste Storage | Disposals | Other Ideas for Disposals | Summary | References

INTRODUCTION :

Radioactive waste management is a complicated technical task and a controversial political issue. The political complexities reflect historical legacies, particularly of World War II and the subsequent cold war, and the long time frames associated with waste management.

These technical characteristic of hazardous waste management creates complex moral, legal, and economic issues. Societies learn from experience but the time between an action and the consequences of that action may be separated by years or centuries. This is a fundamental reason why hazardous waste management activities are often more controversial than other industrial activities. Waste management requires that societies think long term and take actions today to avoid future potential problems. However, this has not been the historical tradition in many societies.

Radioactive Waste :

Radioactive waste is a type of hazardous waste that contains radioactive materials. Radioactive waste is a by- product of various nuclear technology processes. Industries generating radioactive waste include nuclear medicine, nuclear power plant, manufacturing, construction, coal and rare earth mining, and nuclear weapons reprocessing. Radioactive waste is regulated by government agencies in order to protect human health and the environment.

Types of radioactive waste

Radioactive waste includes any material that is either intrinsically radioactive, or has been contaminated by radioactivity, and that is deemed to have no further use. Government policy dictates whether certain materials – such as used nuclear fuel and plutonium – are categorised as waste.

Every radionuclide has a half-life – the time taken for half of its atoms to decay, and thus for it to lose half of its radioactivity. Radionuclides with long half-lives tend to be alpha and beta emitters – making their handling easier – while those with short half-lives tend to emit the more penetrating gamma rays. Eventually all radioactive waste decays into non-radioactive elements. The more radioactive an isotope is, the faster it decays. Radioactive waste is typically classified as either low-level (LLW), intermediate-level (ILW), high-level (HLW), dependent, primarily, on its level of radioactivity.

Low-level waste :

Low-level waste

Low-level waste (LLW) has a radioactive content not exceeding four giga-becquerels per tonne (GBq/t) of alpha activity or 12 GBq/t beta- gamma activity. LLW does not require shielding during handling and transport, and is suitable for disposal in near surface facilities.

LLW is generated from hospitals and industry, as well as the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters, etc., which contain small amounts of mostly short-lived radioactivity. To reduce its volume, LLW is often compacted or incinerated before disposal. LLW comprises some 90% of the volume but only 1% of the radioactivity of all radioactive waste.

Intermediate-level waste :

Intermediate-level waste (ILW) is more radioactive than LLW, but the heat it generates (<2 kW/m3) is not sufficient to be taken into account in the design or selection of storage and disposal facilities. Due to its higher levels of radioactivity, ILW requires some shielding.

ILW typically comprises resins, chemical sludges, and metal fuel cladding, as well as contaminated materials from reactor decommissioning. Smaller items and any non-solids may be solidified in concrete or bitumen for disposal. It makes up some 7% of the volume and has 4% of the radioactivity of all radioactive waste.

High-level waste :

High-level waste

High-level waste (HLW) is sufficiently radioactive for its decay heat (>2kW/m3) to increase its temperature, and the temperature of its surroundings, significantly. As a result, HLW requires cooling and shielding.

HLW arises from the ‘burning’ of uranium fuel in a nuclear reactor. HLW contains the fission products and transuranic elements generated in the reactor core. HLW accounts for just 3% of the volume, but 95% of the total radioactivity of produced waste. There are two distinct kinds of HLW:

  • Used fuel that has been designated as waste.
  • Separated waste from reprocessing of used fuel.

HLW has both long-lived and short-lived components, depending on the length of time it will take for the radioactivity of particular radionuclides to decrease to levels that are considered non- hazardous for people and the surrounding environment. If generally short-lived fission products can be separated from long-lived actinides, this distinction becomes important in management and disposal of HLW. HLW is the focus of significant attention regarding nuclear power, and is managed accordingly.

Very low-level waste :

Exempt waste and very low-level waste (VLLW) contains radioactive materials at a level which is not considered harmful to people or the surrounding environment. It consists mainly of demolished material (such as concrete, plaster, bricks, metal, valves, piping, etc.) produced during rehabilitation or dismantling operations on nuclear industrial sites. Other industries, such as food processing, chemical, steel, etc., also produce VLLW as a result of the concentration of natural radioactivity present in certain minerals used in their manufacturing processes. The waste is therefore disposed of with domestic refuse, although countries such as France are currently developing specifically designed VLLW disposal facilities.

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