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Sci Tech
Metallic fuel for fast breeders after 2020
R. PRASAD
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The scientists are aiming at a breeding ratio of 1.5 for the metallic fuel
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.— Photo: K. Pichumani
Going metallic: The entire fuel core of the Fast Breeder Test Reactor (FBTR) will be changed to metallic fuel by 2017
Fast breeder reactors (the sixth reactor onwards) that would come up after 2020 will be 1,000 MW and not 500 MW reactors. And they would have metallic fuel and not mixed oxide fuel. The entire fuel core of the Fast Breeder Test Reactor (FBTR) would be changed to metallic fuel by 2017. “We are getting ready to irradiate advanced metallic fuel in FBTR by 2010,” said Dr. Baldev Raj, Director of the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam.
Pilot facility
A facility to fabricate, reprocess and refabricate metallic fuel would come up at IGCAR and become operational by 2014. IGCAR is first setting up a pilot reprocessing facility at its complex.
The need to go in for a metallic fuel is understandable. The ability to put up new fast breeder reactors depends on the amount of plutonium available. Breeder technology, as the name indicates, produces or “breeds” more plutonium than it consumes for producing energy.
Self-sustaining
Hence fast breeder reactors are not only self-sustaining but have the capability to produce extra plutonium to start new reactors.
The rate at which surplus plutonium is produced depends on the fuel used in a fast breeder reactor. In the case of mixed carbide fuel used in the FBTR, the extra plutonium produced would be 0.2-0.3 (breeding ratio being 1.2-1.3); it would be just 0.1 (breeding ratio being 1.1) in the case of oxide fuel.
However, in the case of metallic fuel the plutonium gain would be 0.3-0.5. The breeding ratio is 1.3-1.5.
“We are aiming at a breeding ratio of 1.5 against 1.3 which is the norm,” said Dr. Raj.
Faster doubling time
The higher the breeding ratio, the faster would be the doubling time — (time taken to produce surplus plutonium to start a new reactor).
So the doubling time would be the least in the case of metallic fuel and the most in the case of oxide fuel.
“We would have at least 15 years’ advantage to get the necessary fuel [plutonium] for another 1,000 MW reactor,” said Dr. Raj.
The plutonium content of 20-25 per cent in metallic fuel would be the same as in carbide or oxide fuel.
“But there are no lighter elements like oxygen or carbon to absorb the neutrons [in metallic fuels],” explained Dr. Raj on why metallic fuels have a higher breeding ratio and hence faster doubling time.
The reprocessing of metallic fuel will be very different from other fuels.
“The reprocessing technology is very difficult,” he said, “it will be a pyro-metallurgical route.”
Though the FBTR fuel core would be changed from carbide to metallic, it would not be possible to do the same with the Prototype Fast Breeder Reactor (PFBR) or the two reactors coming up at Kalpakkam.
Design constraint
“We can’t put metallic fuel in these reactors as the design does not permit it,” he said, “though it is a desired situation.”
But he and the scientists at Kalpakkam have not given up on the idea. “We will continue to explore ways of doing this,” he said, sounding optimistic.
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