Why India’s top nuclear scientist wants thorium in its reactors sooner

With the world transiting from uranium to thorium, the appeal for PHWRs will grow particularly in emerging economy countries, Kakodkar, the former Chairman of the Atomic Energy Commission, who now holds the position of the Chancellor at the Homi Bhabha National Institute and the Chairman of the Rajiv Gandhi Science & Technology Commission, told The Indian Express in an interview. Edited excerpts:

After the passage of the SHANTI Act, the government seems veering around to the view that opening up of this strategic atomic energy sector is to primarily access external funding, rather than source foreign technology. So, would it be safe to presume that indigenous PHWRs would continue to be the mainstay of the future capacity addition plans?

Unlike other energy forms, nuclear reactors are fuel producers as well, alongside their role as energy producers. Leveraging this feature is important for a country like India which has large energy needs with very insufficient energy resources.

National nuclear energy and nuclear fuel recycle policy thus remains an important guiding force, along with economic considerations, for driving the choice of nuclear reactor systems and their growth. Since the fuel recycle activities have to remain within the government, nurturing a symbiotic and mentoring relationship between the government and the public or private sector utilities holds utmost importance.

The PHWR system has been developed as a part of our well conceived approach to India’s self-reliance, and long-term energy security or independence, to be realised through India’s globally-largest thorium resources. Barring molten salt reactors (MSRs), which are yet to mature, PHWRs are the best platforms for utilising thorium among thermal reactors.

Most importantly, PHWR has also established itself as a robust, safe and economically competitive technology, and thus offers significant attraction to investors — while also taking India’s nuclear energy policy forward. It would thus be natural to expect domestic PHWR to occupy a major share of the 100 gigawatt electric (GWe) nuclear mission (to be implemented between now and 2047) with imported LWRs occupying most of the remaining share.

The large-scale deployment of FBRs, or fast breeder reactors (it is the vital second stage in the DAE’s three-stage power programme that uses recycled fuel and breeds much more fuel at the end of a reaction cycle), is still a work-in-progress. In order to catch up, how compelling is the need for a quick solution to tide over the slowdown in nuclear capacity addition rate due to fuel supply constraints?

Although the commercial uranium and thorium resources are roughly equal globally, nuclear energy programmes naturally began with uranium since the only naturally available fissile isotope is uranium 235. However, there appears to be a political/global security related constraint in adopting uranium recycling by most countries, drastically reducing uranium’s energy potential.

Rapid growth in nuclear energy programmes that is on the anvil worldwide, and a reluctance to recycle uranium is expected to create supply-demand mismatch and related uranium supply security challenges that could hit India in the next 10-15 years.

Large fast breeder reactor (FBR) capacity, particularly fueled by metallic fuel, that breeds nuclear fuel more efficiently, are very important and their large scale electricity contribution is a very compelling national necessity.

Is there a solution in looking at fuel cycle options rather than reactor options. If the likely plan is to continue with PHWRs, how important is it to explore introducing thorium at an earlier stage than envisaged in our original three-stage programme? In that context, how important is the possibility of exploring the irradiation of thorium, along with high assay low enriched uranium, in PHWRs at scale? To deploy the recycled used fuel, is there a need to set up additional power generation capacity, including through molten salt reactors?

The reactor option has to necessarily depend on the nuclear fuel cycle option. It seems to me that days of natural and low enriched uranium fuel cycle will soon get past their peak. The capacity that global uranium resources can sustain in once-through mode is around 550-750 GWe (assuming a reactor life of 60 years), whereas the nuclear capacity of ~1,400 GWe by the year 2050 has been projected by the World Nuclear Association.

While the fast breeder reactors remain critical for our long-term energy security and nuclear fuel supply, including from thorium, we are unlikely to reach the scale required for their deployment to sustain power capacity growth when uranium shortages start constraining it.

Fast reactor technology has to evolve through a few technology transitions such as oxide-fueled reactors, metallic-fueled reactors, and related-fuel cycle technologies. Thus, there are around two to three decades gap before one can think of fleet mode deployment of these reactors, and leverage them for thorium irradiation at scale in accordance with our three stage programme strategy.

This is where fleet mode construction of PHWRs, that is ongoing, comes in handy. Using HALEU-thorium (a new type of fuel that blends thorium with a more concentrated type of uranium called HALEU, or high-assay low-enriched uranium) fuel in PHWRs, without any significant design change, opens an earlier parallel path to thorium irradiation at scale while also gaining advantages of reduced spent fuel inventory, greater economy, uranium saving, and greater safety.

This should enable earlier initiation of the third stage with thorium molten salt reactors (TMSRs are supposed to be developed as part of the three-stage programme) in about 15 years from now. Irradiated thorium input from fast reactors, whenever available at scale, will augment the third stage deployment momentum.

How valid is the argument that the PHWRs are out of sync with the PWRs used by most countries? To what extent is that a deterrent for India to emerge as an exporter of technology?

It is true that light water reactors (both PWRs, or pressurised water reactors and BWRs, or boiling water reactors) have been the more popular reactors. PWRs particularly evolved out of the compact submarine reactor technology.

These technologies had an earlier entry and still dominate the market. However, PHWR technology has enabled us to be self-reliant and economically competitive. With the world transiting from uranium to thorium, appeal for PHWRs will grow, particularly in emerging economy countries.

HALEU is the fuel of choice in many advanced designs that are knocking the door. India, thus, has a significant export opportunity with HALEU-thorium fuel in PHWRs.

How important is it to have our own technology, and not remain dependent on outside technology?

Self-reliance is the key to guard against external vulnerabilities and has always guided our approach to autonomous development of the country’s nuclear capability. That said, collaboration that brings in complementary capabilities on the table is the credible way forward.

Instead of looking at international co-operation as vendor-buyer relationships, we should design mutually beneficial collaborations that respect rights of all participants. When we collaborate from a position of strength, we emerge stronger. The fact is, that we must shift to domestic thorium from the present import dependency of uranium as early as possible.

We do not have reactor platforms for accelerated irradiation testing. On the other hand, we have a wealth of thorium-related experience. Thus, win-win collaborations can be stitched together without compromising self-reliance.

Small modular reactors (SMR) are a new buzzword in the nuclear industry. Given that India already has the largest experience in the small reactor category through its 220 megawatt electrical (MWe) PHWRs, does this offer a better SMR pitch than technologies that are yet to be certified in the vendor’s home market?

Absolutely! 220 MWe PHWR is a successful small reactor with an unparalleled experience base. Modularisation is an engineering exercise to realise intended benefits. Even large reactors have been modularised.

One should get going with deploying 220 MWe PHWRs for captive clean energy supply, with modularisation happening progressively. Industry can do this with a healthy mentoring ecosystem between the DAE (Department of Atomic Energy) and the industry.