Insights into Editorial: Fast Forwarding to Thorium
03 November 2015
The critical shortage of fissile material has prevented the large-scale deployment of thorium-fuelled reactors in India. Due to this, the construction of the advanced heavy-water reactor (AHWR) has also been put off several times since it was first announced in 2004.
India has very modest deposits of uranium and some of the world’s largest sources of thorium. Keeping this in mind, in 1954 Homi Bhabha envisioned India’s nuclear power programme in three stages to suit the country’s resource profile.
India’s three stage nuclear power programme:
The Indian nuclear power programme, launched in 1954, envisaged a three-stage development of nuclear power generation from the country’s uranium and thorium resources.
- In the first stage, heavy water reactors fuelled by natural uranium would produce plutonium.
- The second stage would initially be fuelled by a mix of the plutonium from the first stage and natural uranium [It contains 0.7% uranium-235, 99.3% uranium-238, and a trace of uranium-234 by weight (0.0055%)]. This uranium would transmute (Transmutation is the conversion of an atom of one element to an atom of another through nuclear reactions. Induced nuclear transmutation is transmutation which is induced by scientists by striking the nuclei with high volume particles) into more plutonium and once sufficient stocks have been built up, thorium would be introduced into the fuel cycle to convert it into uranium 233 for the third stage.
- In the final stage, a mix of thorium and uranium fuels the reactors. The thorium transmutes to U-233 as in the second stage, which powers the reactor. Fresh thorium can replace the depleted thorium in the reactor core, making it essentially a thorium-fuelled reactor even though it is the U-233 that is undergoing fission to produce electricity.
With 500 MW Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, India is finally ready to start the second stage. However, experts estimate that it would take India many more Fast Breeder Reactors and at least another four decades before it has built up a sufficient fissile material inventory to launch the third stage.
How to overcome the shortage of fissile material (plutonium)?
India can overcome the shortage of fissile material by procuring it from the international market.
Are there any hurdles in procuring plutonium?
- There is also no law that expressly forbids the procurement of this fissile material. Most nuclear treaties such as the Convention on the Physical Protection of Nuclear Material address only U-235 and U-233, presumably because plutonium has so far not been considered a material suited for peaceful purposes.
- Even the Non-Proliferation Treaty (NPT) merely mandates that special fissionable material — which includes plutonium — if transferred, be done so under safeguards.
- Thus, the legal rubric for safeguarded sale of plutonium already exists. The physical and safety procedures for moving radioactive spent fuel and plutonium also already exists.
How this procurement would help other countries?
If India were to start purchasing plutonium and/or spent fuel, it would immediately alleviate the pressure on countries like Japan and the U.K. who are looking to reduce their stockpile of plutonium.
Why there is an emphasis on thorium technology:
- Thorium reactors produce far less waste than present-day reactors.
- They have the ability to burn up most of the highly radioactive and long-lasting minor actinides that makes nuclear waste from Light Water Reactors a nuisance to deal with.
- The minuscule waste that is generated from these reactors is toxic for only three or four hundred years rather than thousands of years.
- Thorium reactors are cheaper because they have higher burnup.
- Thorium reactors are significantly more proliferation-resistant than present reactors. This is because the U-233 produced by transmuting thorium also contains U-232, a strong source of gamma radiation that makes it difficult to work with. Its daughter product, thallium-208, is equally difficult to handle and easy to detect.
Nuclear power is the fourth-largest source of electricity in India after thermal, hydroelectric and renewable sources of electricity. However, recent incidents like Fukushima incident have raised concerns over the safety of nuclear reactors. Concerns are also being raised over the nuclear waste which the plant generates. Hence, before the government proceeds further, it is necessary to address all these concerns.