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Sci Tech
PFBR: work on to increase the burn-up by 50 per cent
The current burn-up target for the mixed oxide fuel in the PFBR is 1 lakh MW days/tonne. The scientists at the Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam are striving to increase this by 50 per cent to 1,50,000 MW days/tonne.
The rationale
The rationale behind increasing the burn-up is to get more energy from a unit mass of the fuel. But more importantly, the scientists want to increase the time between two fuel handling campaigns from 8 to 12 months. Increasing the burn-up would give them more time between fuel campaigns.
This is analogous to increasing the time interval between fuel refills of a motor vehicle by improving its fuel efficiency by 50 per cent so that a litre of fuel lasts longer.
With 50-60 sub-assemblies containing 217 fuel pins per sub-assembly taken out during each fuel changing campaign, fuel reprocessing and refabrication have to be completed by the time the next fuel campaign is due.
The 8 months cooling period poses an additional challenge.
“Future fuel handling campaigns will be at 12-month interval. So if we develop the technology to reprocess a 12- month-cooled fuel, then we are like online,” said Dr. Baldev Raj, Director of IGCAR.
Target 2011
IGCAR is working on an advanced oxide fuel that would help have a burn-up of 1,50,000 MW days/tonne. The Director is confident that they would be able to achieve this by 2011.
Incidentally, the advanced oxide fuel will have no changes in the fuel composition.
Unlike the mixed carbide fuel, it is the clad (metal that cases the fuel) and wrapper that set the limit for achieving higher burn-ups. So improving the steel used in making the clad and wrapper would make it an advanced oxide fuel.
The shift
“We are working on changing the composition and thermo-mechanical treatment of the steel used for making the clad and wrapper,” said Dr. Raj, “so the shift is from fuel to metallurgy for achieving a higher burn-up.” He is even confident of increasing the burn-up to 2,00,000 MW days/tonne by 2015.
— R.P.
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