Definition #
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. These materials can come from various sources such as nuclear power plants, medical facilities, research laboratories, or industrial processes.
Unlike other hazardous industrial materials the level of hazard of all radioactive waste – its radioactivity – diminishes with time. It decays into non-radioactive elements. Every radionuclide has a half-life – time taken for half of its atoms 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.
Classification of waste #
Radioactive waste is typically classified dependent, primarily, on its level of radioactivity as either low-level (LLW), intermediate-level (ILW), or high-level (HLW) [1].
Low Level Waste (LLW) #
LLW comprises some 90% of the volume but only 1% of the radioactivity of all radioactive waste. It has a radioactive content not exceeding four giga-becquerels per tonne (GBq/t) of alpha activity or 12 GBq/t beta–gamma activity [2].
It’s generated from hospitals and industry, as well as the nuclear fuel cycle and comprises paper, rags, tools, clothing, filters, coverings from nuclear power/research facilities, medical syringes and radiological departments of hospitals. LLW is stored in shallow ditches or metal containers until no longer radioactiv and does not need permanent disposal.
Intermediate Level Waste (ILW) #
ILW comprises some 7% of the volume but only 4% of the radioactivity of all radioactive waste. It 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. Things that generally fall into this category are containers, pumps, filters, medical isotopes and associated medical equipment and parts of decommissioned nuclear reactors. It generally requires shielding, but not cooling [3].
Most ILW is packaged in 500L drums or 3m3 steel boxes, with the waste being immobilised in cement-based materials. These packages are held in interim stores until a suitable disposal route becomes available. As with HLW, the preferred option s for geological disposal.
High Level Waste (HLW) #
High-level waste (HLW) represents 3% of the total volume of nuclear waste but accounts for 95% of the radioactivity. It is sufficiently radioactive for its decay heat to increase its temperature, and the temperature of its surroundings, significantly. As a result, HLW requires cooling and shielding. The preferred option for managing HLW is geological disposal, which involves placing packaged radioactive waste in an engineered, underground repository, where the rock provides a barriers [4].
Spent nuclear fuel (SNF) #
Spent fuel refers to the nuclear fuel that has been used in a reactor. It’s not a liquid green gue, but a solid consisting of small fuel pellets in long metal tubes called rods. A structured group of fuel rods is called a fuel assembly.
Already in the first year after removal from the reactor, 99% of the activity disappears. After 40 years, only one thousandth of the original activity remains. In this case, fuel handling will of course be significantly easier.
Spent fuel reprocessing waste #
Reprocessing of spent nuclear fuel also generates HLW waste.
It includes the chaining of the fuel rods consisting of metal such as zirconium. The chemicals used to extract uranium and plutonium. Byproducts of the reprocessing process
Source #
- Radioactive Waste Management | Nuclear Waste Disposal – World Nuclear Association (world-nuclear.org)
- Low-level waste (LLW-LL) – laradioactivite.com (radioactivity.eu.com)
- Intermediate-level waste (ILW-LL) – laradioactivite.com (radioactivity.eu.com)
- High-level waste (HLW) – laradioactivite.com (radioactivity.eu.com)
