THE HINDU dated 04.11.2004

Breeder reactor: And the winner is... metallic fuel

Unlike oxide fuel, metallic fuel with its higher breeding ratio and shorter doubling time will be able to produce more plutonium to help commission many more nuclear power reactors.

IT IS now official — oxide fuel that is to be used in the 500 MW Prototype Fast Breeder Reactor (PFBR) at Kalpakkam may not be the fuel of choice for future reactors. It is going to be the advanced fuels instead. To be more specific, it will be metallic fuels that will power the future reactors of the country. This brings the curtain down on nitride fuel that was also contemplated as an alternative.

Even two years ago Anil Kakodkar, Secretary, Department of Atomic Energy had expressed the need go the advanced fuel way. But a few scientists were totally opposed to the idea considering the many inherent problems with metallic fuels. So what made the Department finally decide on metallic fuel?

"We should be able to sell electricity at Rs3.25 per unit if the PFBR project completes in time." said Baldev Raj, Director of the Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam. "But our ultimate goal is to sell electricity at Rs3 and even at Rs2.50 per unit." There is a four-pronged approach to accomplish this.

Future fast breeder reactors may well be powered by metallic fuel with a higher breeding ratio in lieu of carbide fuel used in FBTR and oxide fuel to be used in PFBR.

Reducing the capital cost, increasing the plant life from 40 to 60 years, incorporating better safety features and finally achieving 2,00,000MWday/tonne `burn-up' make up the four-pronged strategy. "We are now talking about 1,00,000MWday/tonne burn-up. But with experience we will move to fuels with higher burn-ups," Dr. Kakodkar said.

Fuel `burn-up' in a nuclear reactor refers to the amount of energy extracted from the fuel before it is discharged for storage or reprocessing. Higher the burn-up, lesser will be the fuel cycle cost. Oxide fuel to be used in PFBR has a high potential of reaching 2,00,000MWday/tonne `burn-up'. Why then settle for metallic fuel for future reactors?

Looking beyond burn-up

To arrive at an answer, one has to look beyond the issue of burn-up. The country has embarked on a major programme to generate additional 20,000 MW of nuclear power by 2020. That is just the beginning. Target is to have 30GW and not 20GW by 2020. This can be achieved if and only if many nuclear power plants are commissioned. And for this to happen sufficient nuclear fuel should be available. Unfortunately, India has very little of natural uranium reserves. All efforts are therefore directed to use plutonium produced in the nuclear reactors. And here lies the catch.

Oxide fuel has a low breeding ratio of 1.1, while it is 1.2-1.4 in the case of carbide fuel now being used in the Fast Breeder Test Reactor (FBTR). Compare this with 1.4-1.5 breeding ratio in the case of metallic fuel. Breeding ratio is the amount of extra plutonium produced in a reactor that can be used as a fuel to start another reactor.

Doubling time crucial

A fuel with higher breeding ratio has shorter doubling time. Doubling time is the time taken to generate surplus plutonium to start a new nuclear reactor. So oxide fuel with a meagre 1.1 breeding ratio produces very little extra plutonium compared to metallic fuel. Hence the doubling time is more in the case of oxide and least for metallic fuel. For the record, the doubling time for metallic fuel is ten years while it is thirty years in the case of oxide fuel. "So the second part of the strategy is to have a fuel cycle with shorter doubling time," said Dr. Kakodkar. "And we can start addressing this issue quite early even with the same reactor design."

The doubling time becomes paramount when the country goes on an overdrive to commission new reactors. Oxide fuel thus lost out to metallic fuel on this front. "The mandate is to have metallic fuel in place for all reactors coming up after 2020," Dr. Raj said. "And even the four reactors scheduled to come up by 2020 may have an option of changing from oxide to metallic fuel." Why, the possibility of changing some FBTR sub assemblies to metallic fuel is very high, not to mention the possibility of an entire (fuel) change over to metallic.

Metallic fuel for PFBR?

"Even with the existing design of PFBR, there is a possibility of changing from oxide to metallic fuel," Dr. Kakodkar indicated. Having said this, he pointed out that the initial growth is not dependent on breeding time. "Ultimately, any growth will be based on self generation of plutonium. Though we are not in a hurry to go in for a metallic fuel, sooner the better, " Dr. Kakodkar explained.

According to the Secretary, the priority is to ensure that everything goes fine with PFBR. Making the fuel cycle cheaper and developing the metallic fuel come only next. "But work towards realizing these goals will be undertaken simultaneously," indicated Dr. Kakodkar.

And as usual Dr. Raj and other scientists at IGCAR are confident of not disappointing the Department. "Much data are available on metallic fuel though not on the same scale as oxide," he said. Plans are to be through with all developmental studies relating to metallic fuel by 2015-2016.

A stiff target — considering that many variables are to be studied and mastered. "All R&D efforts at IGCAR will be to study the metallic fuel. To that end, IGCAR as a R&D centre will continue," Dr. Raj noted. And coming back to the question of reducing the cost of power production, Dr. Raj mentioned that if they succeed in developing metallic fuel before PFBR goes critical then the possibility of supplying electricity at Rs3 (and not Rs3.25 as targeted) from 2012 is high. Any decision to this effect can be taken by 2010 when PFBR is to be commissioned. ``We can tell with surety by 2014 when we have plenty of data on metallic fuel," Dr. Raj explained.

Well, the Department may master metallic fuel technology and be equipped to produce sufficient plutonium to commission a new reactor every ten years. But the cost of PFBR construction is pegged at nearly Rs3500 crores. Will the government have sufficient funds to construct reactors at the same pace at which plutonium is produced?

Funding no problem

"As long as the plant productivity is good, money may not be a problem," said Dr. Kakodkar confidently. Dr. Raj concurred with him and was also confident that the Department will not seek monetary support from the Government; it will go to the public instead.

"Even for the PFBR the Government support is only 80 per cent while the remaining 20 per cent will come via equity. And if we are able to demonstrate our mastery over the technology with PFBR then things will be a lot easier," noted Dr. Raj.

They have every reason to be confident. Public support seems to be coming from some unexpected ways. Mumbai based Reliance Energy is already looking at the possibility of setting up nuclear power stations.

And this is the first time a private company has evinced interest in setting up nuclear power plants. Did anyone think India's nuclear power programme would be saddled with fund problems?

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