The indigenously designed and manufactured Prototype Fast Breeder Reactor (PFBR), the crucial link towards India’s aim to harness thorium’s atomic power, continues to miss its deadline to achieve criticality owing to some “teething” problems.
The highly placed official in the Department of Atomic Energy (DAE) whom Nuclear Asia spoke to confirmed that Sodium coolant was poured into the secondary system of the reactor, but the results did not go as per expectations. The fuel loading in the reactor is the next step after coolant pouring.
“Sodium was loaded on to the reactor. Now it is being drained out and moisture-laden CO2 is being passed through it. The whole process takes a lot of time, around 21 days. We do have some small teething problems,” the official told Nuclear Asia on condition of anonymity. He also added that the Atomic Energy Regulatory Board (AERB) is extra cautious as it is a new technology. The main objective of PFBR has been to demonstrate the techno-economic viability of sodium fast reactor for the commercial deployment.
India had embarked on the path to put a closed fuel cycle in place nearly three decades ago.
The PFBR is the second step in India’s three stage closed fuel cycle nuclear energy programme. Indira Gandhi Centre for Atomic Research (IGCAR) has been carrying out the research on sodium-cooled fast breeder reactor technology. A Fast Breeder Test Reactor (FBTR) has been in operation from 1985 onwards. Learning from this a design for 500 MWe Prototype Fast Breeder Reactor has been done. Indigenously produced mix of Uranium and Plutonium Oxide will be used as the fuel in the PFBR. The DAE official, however, assured that the design is not at fault.
The indigenously designed industrial scale PFBR of 500 MWe capacity was expected to go critical in 2010. However, the deadline has since been pushed back several times. It is still not clear when the reactor would achieve criticality.
India aims to gain complete control on fuel cycle through FBRs. A fast breeder reactor produces more fuel than it consumes, while generating energy. Conventional reactors use uranium as fuel and produce some plutonium Breeders produce much more Plutonium, which can be separated and reused as fuel.
The core of a breeder reactor contains fissile uranium and plutonium, atoms that split easily and release energy as heat and radiation. Neutrons released during this reaction are absorbed by a blanket of fertile uranium surrounding the core. Fertile uranium, harder to split than fissile uranium, turns into plutonium when it absorbs neutrons.
Unlike conventional reactors that use water to transfer heat, a breeder uses liquid sodium. The sodium does not slow the neutrons like water, and high energy neutrons are more readily absorbed by the fertile uranium to create plutonium. The sodium surrounding the core flows through a heat exchanger, a cluster of thin-walled metal tubes and transfers its energy to a separate stream of sodium.
The founders of Indian nuclear energy programme emphasised on a closed fuel cycle that would that the country would reprocess and remake the spent fuel from its nuclear power reactors. India has been following a three-stage nuclear electricity programme. The three stages are as follows – pressurised heavy-water reactors (PHWRs) using natural uranium as fuel; fast breeder reactors (FBRs) using plutonium and depleted uranium from the PHWRs; and reactors using the abundant thorium found in India.
Russia is the only country currently operating FBRs. One FBR of 600 MWe capacity called BN-600 has been in operation since 1980. Recently, Russia has commenced operation of BN-800 (800 MWe capacity). China has also started a test reactor of 65 MWt capacity in 2010. Other two reactors JOYO, MONJU in Japan are under shutdown currently. Another power reactor of 1200 MWe capacity is planned to be constructed in Russia for which design is in progress.