old for new . Bringing back reactors for green hydrogen

Now that the centrality of hydrogen in India’s (or any country) climate action has been established, the focus is on ways to produce the gas cheap.

In this, a forgotten nuclear technology can be of immense help. Indeed, India’s commitments at the recent COP26 conference — half the energy consumed should come from non-fossil fuels — cannot be met without bringing in nuclear, a point that was underscored by the well-known nuclear physicist and former chairman of the Atomic Energy Commission Anil Kakodkar, in a recent interview in Business Line .

If India is to achieve ‘net-zero’ emissions by 2070, many more nuclear plants would be needed to increase the capacity from 15,000 MW at present to 22,480 MW by 2031, says Kakodkar. But that is another story.

The more pressing goal is to produce green hydrogen at a dollar a kilogram in one decade. For this to happen with the technologies in hand, prices of solar energy must fall steeply, which appears unlikely. You need 55 kWhr of electricity to produce one kg of hydrogen; given the cost of electrolysers and maintenance, electricity should be available at no more than ₹2 per kWhr, for the ‘$1/kg’ goal.

Enter nuclear. Not only electricity from nuclear plants, but also heat.

In the interview, Kakodkar gave an insight. You can bring down the consumption of electricity if you heat the water. If you make water very hot, you need less energy to split it into hydrogen and oxygen. Now, heating water will need energy. But this heat can be provided cheap by what are known as ‘high-temperature reactors’ (HTR), something which the Bhabha Atomic Research Centre dabbled in decades ago.

Kakodkar says that if you heat water using HTRs and then split the water into hydrogen and oxygen in an electrolyser, the costs could be tamed.

What is this HTR? A good answer to this is available in a presentation made by BARC scientists IV Dulera and RK Sinha at an international conference on non-electric applications of nuclear power, held at Oarai, Japan, from April 16-19, 2007. (Sinha later became Chairman of Atomic Commission.) The presentation focused particularly on hydrogen and desalination.

It spoke of an Indian HTR development programme, which had two elements: a 100 kW (thermal), 1,000 degrees C portable ‘compact high-temperature reactor’ (CHTR) for technology demonstration; and, importantly, a 600 MW (thermal), 1,000 degrees C ‘Indian high-temperature reactor-hydrogen’, or IHTR-H. These two reactors would be powered by ‘TRISO-coated particle’ fuel. TRISO — ‘tristructural isotropic’ — comprises uranium, carbon and oxygen, all of which India can make.

The IHTR-H is designed to produce about 7,000 kg of hydrogen, 18 MWhr (thermal) of energy per hour and 9 million litres of water a day.

From the presentation, it is clear that this is not just a concept. Detailed designs of both reactors (CHTR and IHTR-H) have been made. These reactors are capable of unattended operations for many years.

“In future Indian energy scenario, nuclear energy-assisted hydrogen production is expected to play a significant role; development of technologies related to high-temperature nuclear reactors is an important step in that direction,” Dulera and Sinha say in the presentation, adding that R&D has been initiated for most of the work.

Clearly, BARC has thought of hydrogen production as far back as 2007, when hydrogen was not the buzzword it is today.

But what happened to the programme? “It has not been shelved, it is on,” a senior official of the Department of Energy told Business Line , but couldn’t give more details. Kakodkar sees IHTRs as the way ahead for low-cost production of green hydrogen.

Meanwhile, another evolution in the nuclear world has the potential to help India keep its net-zero promise — small modular reactors, or SMRs — which could be eased into the sites vacated by decommissioned coal-fired power plants.

India is no stranger to small reactors, having operated 220 MW reactors for many years, which are not offered for exports. INS Arihant, India’s nuclear submarine, is powered by an 83 MW pressurised light water reactor.

However, the SMRs that have grabbed the world’s attention differ in design from the conventional small-sized reactors. According to the International Atomic Energy Agency, over 70 SMR designs are being worked on in 18 countries.

Kakodkar has suggested that India could have a small-sized reactor programme running concurrently with the large projects.

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