India’s Fast Breeder Test Reactor attains design power level of 40 MW

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India’s Fast Breeder Test Reactor (FBTR) at Kalpakkam in Tamil Nadu state attained its design power level of 40 megawatts thermal (MWt) earlier this month, according to the Indira Gandhi Centre for Atomic Research (IGCAR). 

This sodium cooled FBTR, based on the French reactor Rapsodie, attained its first criticality in October 1985 and, thus, achieved its full design power level for the first time in over 36 years since it started operating.  

A reactor with a small core, it is the first of its kind in the world to use plutonium-uranium mixed carbide as a driver fuel. The FBTR, which has a key role in India’s three-stage nuclear power programme aimed at a thorium-based closed fuel cycle, had earlier attained the maximum power level of 32 MWt that was accomplished in 2018. 

According to the IGCAR Director B. Venkatraman, the power of the reactor was gradually raised by adding fresh fuel sub-assemblies based on the performance of the mixed carbide fuel in terms of fuel liner heat rating and burn-up. 

He said that for raising the FBTR power, the core of the reactor was converted to a new 40 MWt core.  

“After getting AERB (Atomic Energy Regulatory Board) clearance, the FBTR was converted to a new 40 MWt core and all the reactor physics parameters were measured to ensure safety. Reactor was re-started with a new core and power was raised to 40 MWt”, he said.  

The main aim of the FBTR is to provide experience in fast reactor operation, large scale sodium handling and to serve as a test bed for irradiation of fast reactor fuels and materials. 

India’s nuclear power programme was conceived in the late 1960s as a closed fuel cycle to be achieved in three stages. The spent fuel generated from one stage would be reprocessed and used in the next stage of the cycle to produce power. Thus, the closed fuel cycle was designed to “breed” fuel and to minimise generation of nuclear waste. This three-stage nuclear power program in India had been conceived with the ultimate objective of utilising the country’s vast reserves of thorium-232. India has the world’s third largest reserves of thorium. 

The first stage envisages the use of pressurised heavy water reactors (PHWRs) to produce energy from natural uranium. Besides energy, PHWRs also produce fissile plutonium (Pu)-239. The second stage involves using the indigenous fast breeder reactor technology fuelled by Pu-239 to produce energy, as well as more Pu-239. By the end of the second stage of the cycle, the reactor would have produced, or “bred” more fissile material than it would have consumed. 

The final stage of the cycle would involve the use of Pu-239 recovered from the second stage, in combination with thorium-232, to produce energy and uranium (U)-233 using “thermal breeders”. This production of U-233 from thorium-232 would complete the cycle, while the U-233 would then be used as fuel for the remaining part of the fuel cycle.