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P K Wattal, director, Nuclear Recycle Group of the Bhabha Atomic Research Centre, Trombay, offers insight into the status of nuclear waste disposal in the country in an e-mail interview with Ankur Paliwal
India has a policy to reprocess spent fuel. It is said that only 2-3 per cent of the spent fuel generated from our nuclear reactors is actually waste and the rest can be reprocessed. Is it true? How do we dispose of this waste?
India has adopted closed fuel cycle option, which involves reprocessing and recycling of the spent fuel. During reprocessing, 2-3 per cent of the spent fuel becomes waste and the rest is recycled. This 2-3 per cent waste, called high level liquid waste (HLW), is converted into glass through a process, called vitrification. The vitrified waste has to be stored for 30-40 years for cooling. We have Solid Storage Surveillance Facility with constant cooling and surveillance for interim storage of vitrified waste canisters at Tarapur (in Maharashtra). Another such facility is being constructed at Kalpakkam (in Tamil Nadu). These storage facilities have enough capacity for the vitrified wastes that will get generated in the next 30-40 years.
If only 2-3 per cent of the spent fuel is high radioactive waste, then what is intermediate level radioactive waste and low level radioactive waste? And how are they disposed of?
Intermediate level liquid waste (ILW) and low level liquid waste (LLW) also get generated during reprocessing and vitrification. Depending upon their nature and activity levels, LLW is diluted to bring down the radioactivity to acceptable levels and discharged. ILW is treated for volume reduction and stored in cement matrices.
Has the pilot plant on separating the waste from spent fuel become operational?
High level liquid waste (HLW) contains mostly fission products and minor actinides. Among the fission products, Cesium (Cs) and Strontium (Sr) with half lives of about 30 years are predominant. After 10 half lives (300 years), radioactivity on account of Cs and Sr becomes insignificant. Minor actinides like Americium (Am), Neptunium (Np) and Curium (Cm) have half lives in the range of 1,000 years and one million years, and need special attention. The separation of these long-lived minor actinides from fission products is called “partitioning” of high level waste. A pilot plant for separation of this long-lived minor actinides from fission products in high level waste has been set up at Tarapur. The plant is undergoing commissioning and shall be operational soon.
Where are we reprocessing our spent fuel? Would the spent fuel from all the nuclear plants be transported to these sites?
We have three reprocessing plants at three different sites: Tarapur and Trombay in Maharashtra, and Kalpakkam in Tamil Nadu. These are currently under operation. The spent fuel from the other nuclear power plants is reprocessed in these plants depending on their proximity to the plant.
How much nuclear waste does India have?
The amount of waste generation is dependent on the total amount of reprocessing carried out in that year. We are continuously reprocessing the spent fuel. The inventory of plutonium cannot be divulged because it is our national policy. (Plutonium, or Pu239, is released during reprocessing, which is used as a fuel in stage-2 nuclear reactors).
Has the stage-2 nuclear fast breeder reactor become operational which will run on reprocessed fuel? Have we built up enough inventory of Pu239 to run it?
For Stage-2 of our nuclear programme, fast breeder test reactor is under operation for about 30 years. A prototype fast breeder reactor (PFBR) is under construction at Kalpakkam and will be operational by the end of this year. We have enough inventory of Pu239 to run it.
How far are we from building a geological repository to store nuclear wastes permanently?
The need for a deep geological repository would arise only after 30-40 years. This is because, the inventory of the vitrified high level waste needs to be kept under cooling and surveillance for 30-40 years before it is placed in a deep geological repository. However, R&D activities in the area of geological disposal have been undertaken involving host rock characterisation and interaction with the waste products, thereby generating comprehensive data for eventual setting up of underground repository in future. Public participation and involvement of local communities is one of the important considerations for the site selection of a deep geological repository.