Fast forwarding to thorium

A new worldwide plutonium market brought under safeguards is a safe bet to help India advance its ambitious thorium reactor programme.

November 03, 2015 01:13 am | Updated November 18, 2016 04:04 am IST

What is the single greatest factor that prevents the large-scale deployment of >thorium-fuelled reactors in India ? Most people would assume that it is a limitation of technology, still just out of grasp. After all, the construction of the advanced heavy-water reactor (AHWR) — a 300 MWe, indigenously designed, thorium-fuelled, commercial technology demonstrator — has been put off several times since it was first announced in 2004. However, scientists at the Bhabha Atomic Research Centre have successfully tested all relevant thorium-related technologies in the laboratory, achieving even industrial scale capability in some of them. In fact, if pressed, India could probably begin full-scale deployment of thorium reactors in ten years. The single greatest hurdle, to answer the original question, is the critical shortage of fissile material.

A fissile material is one that can sustain a chain reaction upon bombardment by neutrons. Thorium is by itself fertile, meaning that it can transmute into a fissile radioisotope but cannot itself keep a chain reaction going. In a thorium reactor, a fissile material like uranium or plutonium is blanketed by thorium. The fissile material, also called a driver in this case, drives the chain reaction to produce energy while simultaneously transmuting the fertile material into fissile material. India has very modest deposits of uranium and some of the world’s largest sources of thorium. It was keeping this in mind that in 1954, Homi Bhabha envisioned India’s nuclear power programme in three stages to suit the country’s resource profile. 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. This uranium would transmute 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.

After decades of operating pressurised heavy-water reactors (PHWR), India is finally ready to start the second stage. A 500 MW Prototype Fast Breeder Reactor (PFBR) at Kalpakkam is set to achieve criticality any day now and four more fast breeder reactors have been sanctioned, two at the same site and two elsewhere. However, experts estimate that it would take India many more FBRs and at least another four decades before it has built up a sufficient fissile material inventory to launch the third stage. The earliest projections place major thorium reactor construction in the late 2040s, some past 2070. India cannot wait that long.

Procuring fissile material

The obvious solution to India’s shortage of fissile material is to procure it from the international market. As yet, there exists no commerce in plutonium though there is no law that expressly forbids it. In fact, 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. 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.

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. India is unlikely to remain the only customer for too long either. Thorium reactors have come to be of great interest to many countries in the last few years, and Europe yet remains intrigued by FBRs as their work on ASTRID, ALFRED, and ELSY shows.

The unseemly emphasis on thorium technology has many reasons. One, thorium reactors produce far less waste than present-day reactors. Two, 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. Three, the minuscule waste that is generated is toxic for only three or four hundred years rather than thousands of years. Four, thorium reactors are cheaper because they have higher burnup. And five, 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.

The mainstreaming of thorium reactors worldwide thus offers an enormous advantage to proliferation-resistance as well as the environment. Admittedly, there still remains a proliferation risk, but these can be addressed by already existing safeguards. For India, it offers the added benefit that it can act as a guarantor for the lifetime supply of nuclear fuel for reactors if it chooses to enter the export market, something it is unable to do for uranium-fuelled reactors.

It is clear that India stands to profit greatly from plutonium trading but what compelling reason does the world have to accommodate India? The most significant carrot would be that all of India’s FBRs that are tasked for civilian purposes can come under international safeguards in a system similar to the Indo-U.S. nuclear deal. There is little doubt that India will one day have a fleet of FBRs and large quantities of fissile material that can easily be redirected towards its weapons programme. This will limit how quickly India can grow its nuclear arsenal to match that of, say, China. Delhi has shown no inclination to do so until now, but the world community would surely prefer that as much as possible of India’s plutonium was locked under safeguards.

The U.S. could perhaps emerge as the greatest obstacle to plutonium commerce. Washington has been resolutely opposed to reprocessing since the Carter administration, preferring instead the wasteful once-through, open fuel cycle. Although the U.S. cannot prevent countries from trading in plutonium, it has the power to make it uncomfortable for them via sanctions, reduced scientific cooperation, and other mechanisms. The strong non-proliferation lobby in the U.S. is also likely to be nettled that a non-signatory of the NPT would now move to open and regulate trade in plutonium. The challenge for Delhi is to convince Washington to sponsor rather than oppose such a venture. In this, a sizeable portion of the nuclear industry could be Delhi’s allies.

Scientists predict that the impact of climate change will be worse on India. Advancing the deployment of thorium reactors by four to six decades via a plutonium market might be the most effective step towards curtailing carbon emissions.

(Jaideep A. Prabhu is a researcher in foreign and nuclear policy. He can be reached at @orsoraggiante)

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