Why isn’t India using their Thorium power to generate energy?
India is following a three-stage nuclear power programme (that was formulated by Dr. Homi Bhabha in the 1950s). The ultimate focus of the programme is on enabling the thorium reserves of India to be utilised in meeting the country’s energy requirements.
So, the third stage will use thorium. This third stage will come only when the first two stages are completed. Lets see why –
1. Stage one centers on India’s indigenous pressurized heavy water reactors (PHWRs), which are based on Canadian CANDU reactors. India currently has 18 operational PHWRs with four more being built. These use 235U as the fuel. But they also generate Plutonium (reprocessed from the spent fuel). This plutonium in used in the second stage.
2. In stage two, Fast Breeder Reactors will use thorium and plutonium(reprocessed from the first stage’s spent fuel) to further generate plutonium and 233U. The first commercial 500 MW fast breeder is nearly complete at the Indira Gandhi Centre for Atomic Research in the state of Tamil Nadu.
3. Thorium is front and center in the final third stage, on which India’s long-term nuclear power supply depends. The goal is to utilize an 80-20 mix of thorium and uranium oxide fuels with plutonium as the trigger fuel to breed yet more 233U. The first two stages will build up enough fissile uranium and plutonium for this.
So, why is India not directly using thorium ?
This is because thorium itself is not a fissile material, and thus cannot undergo fission to produce energy. Instead, it must first be converted into the fissile isotope uranium-233 by transmutation in a reactor fueled by other fissile materials. The first two stages, natural uranium-fueled heavy water reactors and plutonium-fueled fast breeder reactors, are intended to generate sufficient fissile material from India’s limited uranium resources, so that all its vast thorium reserves can be fully utilised in the third stage of thermal breeder reactors.
Quoting Bhabha ” The first generation of atomic power stations based on natural uranium can only be used to start off an atomic power programme… The plutonium produced by the first generation power stations can be used in a second generation of power stations designed to produce electric power and convert thorium into U-233, or depleted uranium into more plutonium with breeding gain… The second generation of power stations may be regarded as an intermediate step for the breeder power stations of the third generation all of which would produce more U-233 than they burn in the course of producing power.”
Indian scientists and engineers at BARC have developed the unique 300 MW AHWR for thorium utilization.
However, there are some problems –
1. Long lasting expectation of the reactor - the designers want it to last a 100 years, compared to the 40-year design life for current reactors.That puts significant challenges on the materials of construction like concrete and steel.
2. Recycling of spent fuel - The key challenge with the thorium fuel cycle is the recycling of spent fuel. It’s very difficult because you have to separate three streams: thorium, uranium, and plutonium,” The gamma-emitting 232U in the spent fuel, which makes weapons proliferation harder, also complicates thorium separation. You need shielded facilities that become costly. Indian scientists have only done this separation at a small experimental scale so far.
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