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
|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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