Any human activity generates waste, which has no useful application. Radioactive waste, for some reason or the other has been a controversial and emotional topic with public. In view of this, radioactive wastes generated from peaceful applications have been subjected to very stringent regulatory control as compared to other type of waste. Waste management means the whole sequence of operations starting with the generation of waste, segregation of waste, and ending with safe disposal. When properly managed, the radioactive waste is expected to deliver negligibly small radiation doses to people, present and future.

Waste that contains such a low concentration of activity that it does not need to be treated differently from ordinary non-radioactive waste is termed as Exempt waste. Mining and processing of uranium and thorium containing ores/minerals minerals generate large amounts of waste containing fairly low concentrations of naturally occurring radionuclides. This type of waste is called NORM (naturally occurring radioactive material) waste and a good example of NORM waste is tailings from the mines and milling operations. The NORM waste is normally disposed in earthen pond covered with a few meters of earth (Tailings Pond).

Operations involving handling of open or sealed radioactive materials / sources generate various categories of radioactive wastes. Broadly, the waste is categorized as solid, liquid and gaseous waste. Further categorization is based on activity concentration (for liquid waste and gaseous wastes) and based on dose rate on the surface of the waste packet in case of solid waste.

Waste containing alpha activity and high activity content are managed separately and safely. The radiation characteristics, like activity level, half-life, radiation emission types and energy of the emissions, play an important role in the management of the waste. Accordingly, they are classified as exempt waste, very low-level, low-level, intermediate level and high-level waste. Waste containing natural radionuclides are classified as NORM waste.

Disposal of radioactive waste

Philosophy of radioactive waste management

The basic philosophy of radioactive waste management embodies three basic principles:

  1. Delay and Decay - followed generally for waste containing short-lived radionuclides
  2. Dilute and Disperse – followed in case of low active liquid effluents, and
  3. Concentrate and Contain in solid matrix – followed in cases of intermediate and high- level wastes.

Facilities handling only sealed sources are not expected to generate any liquid or gaseous wastes. However, the facilities such as nuclear medicine laboratories or research institutions handling unsealed small sources (e.g. radioactive solutions) generate or likely to generate low level radioactive wastes. Generally, such wastes are of short half-life (in days), and in very amounts (micro Curie level). The examples are I-131, I-125, Tc-99m, etc. The wastes may be stored for about 10 half-lives and may be disposed off as ordinary waste as per the applicable regulations.

The available mode of disposal of liquid effluent containing radioactivity at near background or close to zero values is to a water source like sea or municipal sewer. The low-level liquid wastes are disposed off into municipal sanitary sewerage system, probably through a delay tank to reduce activity level of short-lived radionuclides. Solid waste from the hospitals, go for ground burial within the controlled areas or transported to government waste management facilities. Management of cadavers (burning / burial) containing radioactivity from nuclear medicine procedures should be strictly as per the national regulatory requirements.

For nuclear fuel cycle facilities, there are several options available for the disposal of radioactive solid waste. Based on the envisaged disposal method, the solid wastes are segregated into different categories based on the activity type, content and half- life of the radionuclide.

In general, the actual limits on concentration and total activity disposable from a facility depend of the type of radionuclide, physicochemical/biological parameters of the waste, treatment options available, the site characteristics, and exposure limits to the members of the public. Large amount of NORM waste is generated in industrial operations, involving natural radioactive materials, such as burning of coal, uranium mining, exploration of oil, etc.

Disposal of high-level waste in more involved and often may depend on the government policy. The technology to immobilize (i.e., convert into glass form and made insoluble in water) this waste is available, proved, and the plants are operating worldwide. India is one of the very few countries who have mastered this technique. International cooperation and consensus on the approaches on disposal strategies for high level waste are pursued very seriously by the International, non-governmental agencies such as International Atomic Energy Agency (IAEA).