Spent Fuel Processing
The nuclear fuel mix has high amount of fissile material. Once it is used, the amount of non-fissile material and by-products would increase and that material cannot be used again as fuel in its present form. This is called spent fuel. It may or may not be re-usable. If spent fuel is not reprocessed, the fuel cycle is referred to as an open fuel cycle (or a once-through fuel cycle); if the spent fuel is reprocessed, it is referred to as a closed fuel cycle.
We note here that, India’s nuclear programme is oriented towards maximising the energy potential of available uranium resources and the utilisation of the large thorium reserve. Available global uranium resources cannot sustain the projected expansion of nuclear power without adopting the closed fuel cycle approach.
The nuclear fuel cycle or Nuclear Fuel Chain is the progression of nuclear fuel through a series of differing stages. It has two parts:
- Front End: It includes the preparation of the fuel and steps in the service period in which the fuel is used during reactor operation.
- Back End: Which includes the steps to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. When the spent fuel is reprocessed, it is a closed Fuel Cycle. When the spent Fuel is not reprocessed, it is an open fuel Cycle. India has adopted closed fuel cycle option, which involves reprocessing and recycling of the spent fuel.
During reprocessing, only about two to three percent of the spent fuel becomes waste and the rest is recycled. This waste, called high level waste (HLW), is converted into glass through a process, called vitrification. The vitrified waste is stored in a Solid Storage Surveillance Facility for 30-40 years with natural cooling prior to its disposal in a final disposal facility. The need for a final disposal facility will arise only after three to four decades. This will also provide sufficient time for the reduction in the radioactivity of some of the short-lived radioactive species in the vitrified waste.