New Delhi: Last week, when the first-of-its-kind thorium-based fuel developed by a firm in the United States—Clean Core Thorium Energy (CCTE)—achieved a 45 GigaWatt-days per Metric Ton of Uranium (GWd/MTU) burn-up level at the US Department of Energy’s Idaho National Laboratory, it was not only a breakthrough with potential to redefine the future of nuclear energy, now dependent on uranium. The development is significant for India, too.
India has very limited commercially viable uranium sources, but the world’s largest thorium reserves. Currently, India imports uranium, which contains the only fissile material available in nature, to meet nuclear energy requirements.
India’s target is to generate 100 GW of nuclear energy capacity by 2047.
Soon after the CCTE’s 17 August announcement of the breakthrough, Indian nuclear physicist and former Atomic Energy Commission chairman Anil Kakodkar posted on X, “Congratulations @cleancoreenergy. Reaching around 45 GWd per ton burn-up in Thorium-based ANEEL fuel assures a viable PHWR fuel that can bring thorium molten salt small modular reactors (SMR) into reality sooner than one would have imagined.”
Thorium or Th-232 is a naturally occurring radioactive element. It is found in the Earth’s crust more commonly than uranium, but unlike the uranium isotope, Uranium-235, it cannot directly sustain a chain reaction, required for nuclear fission.
The thorium fuel CCTE developed and patented is ANEEL, an acronym for Advanced Nuclear Energy for Enriched Life. Reaching a high burn-up level signifies maximum energy at every cycle of irradiation in a nuclear reactor. The 45 GWd/MTU burn-up level is six to seven times the average discharge burn-up for Pressurised Heavy Water Reactors (PHWR) and CANDU (Canadian Deuterium Uranium, a Canadian pressurised heavy water reactor design) reactors, designed to use natural uranium fuel.
The US firm said the ANEEL fuel combines thorium with High-Assay Low-Enriched Uranium (HALEU) to offer a “safer, more efficient, and proliferation-resistant alternative for existing and future PHWR and other CANDU reactor fleets worldwide”.
Unable to directly power a reactor, thorium undergoes a process inside a nuclear reactor to transform into a usable fuel. In the reactor, Thorium-232 absorbs a neutron, becoming Thorium-233, which quickly decays into Protactinium-233, and then into Uranium-233.
Uranium-233 is fissile, and each split (fission) releases a large amount of energy, along with more neutrons, which, in turn, strike other Uranium-233 atoms. This repeating cycle is the chain reaction that keeps the reactor running and generating steady heat.
Natural uranium contains 0.7 percent of fissile Uranium-235 and three to five percent of low-enriched uranium used in more common PWRs and BWRs (Boiling Water Reactors). HALEU enriches the uranium fissile content up to 20 percent. For civilian use, the upper limit of enrichment is 20 percent. Beyond 20 percent, there is a concern that one may go closer to highly-enriched uranium, typically required for weapons.
“This achievement outpaces the capabilities of conventional nuclear fuels used in PHWR and CANDU reactors,” CCTE said in a statement.
Kakodkar said the ongoing irradiation experiment will continue till the burn-up reaches 60 GWd/MTU. “When it completes 60 GWd/MTU, we will have a proof, experimental proof that such large burn-ups are realisable,” he said, adding that even 45 GWd/MTU is significant because of the economic viability.
“You get assured even at 45 GWd/MTU. It will improve even further. But, it has already crossed the level where this whole thing will become economically viable…So, that is why I tweeted what I tweeted.”
Also Read: A pick-me-up for India’s lithium dreams: How urban miners are spinning e-waste into white gold
What it means for India
Kakodkar, one of the advisors at CCTE, told ThePrint the development at Idaho National Laboratory brings new “opportunities” for India, which has the world’s largest reserve of thorium. There is uranium production in the country, but it can support only a few GWs of nuclear energy out of the 100 GWs, which India targets by 2047.
“And, if we keep on depending on imported uranium, we will put ourselves into strategic vulnerability,” Kakodkar said.
He said that if India combines thorium and HALEU in heavy water reactors to build up a capacity of Uranium-233, the fuel for molten salt reactors, our nuclear energy requirements may, thereafter, be met using domestically available thorium around the time when uranium supply is increasingly falling short or uranium is entering a volatile market mode.
Molten salt reactors, Kakodkar said, could be reflected upon as “self-sustainable”. “They would support breeding of uranium from thorium. Not as fast as fast reactors would do, but they will become self-sustaining. So, my proposition: while we continue to pursue our three-stage programme, considering the potential uranium volatility in the market, instead of using natural uranium, we use HALEU thorium and quickly become ready for thorium reactors in the form of these molten salt reactors,” he said.
In molten salt reactors, the coolant is a molten salt, not water. The salt liquefies at reactor operating temperature, storing massive amounts of thermal energy at atmospheric pressure. The fuel in these reactors can be molten, and such reactors would be among the safest because there is no chance of core melt. It is already molten.
However, India currently lacks the facilities to construct a molten salt reactor.
Kakodkar said that using HALEU-thorium improves the economics of heavy-water reactors. “The cost of energy from the heavy water reactors would actually become lower. So, there is a strong incentive to do this. And, if you do this, you can not only meet India’s energy requirement, but you can offer a product to the global market where our capital cost is less, primarily because we make PHWR in India.”
This advantage is why India should strategise shifting from uranium to thorium quickly.
“India can get into a big manufacturing hub for heavy water reactors and supply these reactors fuelled by HALEU thorium. As far as reactor technology is concerned, we are already there. India can also supply thorium, considering we have plenty of thorium reserves. I think this could not only meet India’s energy requirement but also create a global export opportunity…whatever the OPEC countries are for the world today, India can become that,” Kakodkar said.
HALEU thorium-fuelled PHWRs will not only be economically competitive, but also, more importantly, there will be no fear of proliferation due to the use of thorium, not U-235.
“I am only pointing out an opportunity, which is very large for energy security of the country, for economic gains of the country, for global energy security and also for climate security worldwide,” he said.
The thorium story
The Earth contains at least as much or more commercially viable thorium as uranium. Unfortunately, thorium does not contain any fissile material like uranium.
If one uses thorium, recycling is a must. In a reactor, just as Uranium-238 becomes fissile plutonium, thorium becomes fissile Uranium-233. Recycling will help realise a larger potential for both thorium and uranium.
“In a nuclear reactor, thorium is a much better fuel material, in the sense that its breeding to fissile material is much more efficient compared to uranium,” Kakodkar said. Thorium has other advantages, in terms of nuclear and thermo-physical properties that enhance safety.
The world has not adapted to recycling uranium, fearing diversion for weapons-making. Thorium, once recycled, will enhance the energy potential available for civilian energy production and almost eliminate concerns over proliferation and diversions.
So far, because nuclear energy use has been limited mostly to advanced countries, there has been no need to develop thorium for energy purposes. With demand for clean energy now growing, nuclear energy will play a more significant role in achieving net-zero targets.
That is why, Kakodkar said, India should focus on thorium. “This ANEEL fuel is a very credible way to be fuel-independent.”
In 2019, India’s atomic energy department’s long-term energy plan involved using available deposits of thorium. The department, in a statement, said its three-stage nuclear power programme will multiply the domestically available fissile resource, using natural uranium in pressurised heavy water reactors.
“The utilisation of thorium, as a practically inexhaustible energy source, has been contemplated during the third stage of the Indian nuclear programme. As is the case with the generation of electricity from uranium, there will be no emission of greenhouse gases from thorium. Therefore, it will be a clean source of energy,” the statement read.
Dr Michael Worrall, the technical lead for the CCTE ATR Irradiation at Idaho National Laboratory, noted in the statement issued by the US firm: “ANEEL’s performance in the ATR is a strong indicator of the promise thorium-based fuels hold in supporting future energy goals and diversifying the nuclear fuel landscape.”
(Edited by Madhurita Goswami)