Context: The commencement of core loading of India's first indigenous Fast Breeder Reactor (500 MW) at Kalpakkam, Tamil Nadu was completed recently. Government of India has formed a dedicated PSU known as Bhartiya Nabhikiya Vidyut Nigam Ltd (BHAVINI) to construct and operate India’s most advanced nuclear reactor-Prototype Fast Breeder Reactor (PFBR). This marks the commencement of second phase of India's three stage nuclear program. This large-scale deployment of nuclear power is accompanied by another issue that of management of nuclear waste.
Generation of Nuclear Waste in Nuclear Fission Reactor
In a fission reactor, neutrons bombard the nuclei of atoms of radioactive Uranium-235 nucleus. When the nucleus of Uranium-235 absorbs a neutron, it leads to fission to Barium-144 and Krypton-89 and three neutrons.
The nuclear debris (Barium-144 & Krypton-89) constitute elements which cannot further undergo fission, they become part of nuclear waste.
Nuclear waste is highly radioactive and needs to be stored in facilities reinforced to prevent leakage and/or contamination of the local environment.
Methods of Handling of Nuclear Waste
Considering the radioactivity levels of nuclear waste have to be isolated from human contact for long periods of time.
- Solid Nuclear Waste Management: Nuclear Waste generated is hot and radioactive and needs to be kept underwater for up to a few decades. Once it has cooled, the nuclear waste is transferred to dry casks for longer-term storage. These is then placed inside large steel cylinders and surrounded by an inert gas. The cylinders are sealed and placed inside larger steel or concrete chambers.
- Geological disposal: Some scientists have argued for nuclear waste is sealed in special chambers and buried underground in granite or clay. This leads to long-term storage away from human activity. However, there are concerns of the nuclear waste being exposed if the containers are disturbed by activities such as digging or mining etc.
- Liquid nuclear waste management:
- Nuclear fission plants generate small quantities of aqueous wastes containing short-lived radionuclides which may be discharged into the environment. For ex. Japan is currently discharging such water from Fukushima nuclear power plant into the Pacific Ocean.
- Some aqueous nuclear waste can be evaporated or chemically precipitated to yield a sludge to be treated and stored, absorbed in solid matrices or incinerated.
- Reprocessing of spent fuel: This refers to technologies wherein there is a separation of fissile material from non-fissile material in the spent nuclear fuel. Reprocessing leads to higher nuclear fuel efficiency. Reprocessing gives access to weapons-usable (different weapons-grade) plutonium. IAEA has specified 8 kgs of Plutonium in which Plutonium-239 accounts for more than 95% to be threshold for 'safeguards significance'. Thus, IAEA tightly regulates the setting up and operations of reprocessing facilities. Reprocessing process is expensive and demands specialised protection and personnel.
- All countries with long term nuclear programs have a considerable inventory of spent fuel running into thousands of tonnes.
Nuclear Waste Handling in India
- Reprocessing facilities in India: India has reprocessing plants in Trombay, Tarapur & Kalpakkam.
- In-situ management: Nuclear wastes generated at nuclear power stations during their operation are of low and intermediate radioactivity and are mostly managed at the site itself. Such facilties are located at all nuclear power plants and is monitored for radioactivity.