The Prototype Fast Breeder Reactor (PFBR), under construction at Kalpakkam, near Chennai, is “a unique reactor” which does not require water for emergency cooling of its nuclear fuel core in the case of an accident, said Baldev Raj, who laid down office on Saturday as Director, Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam. The 500 MWe PFBR will be commissioned in 2012.
(The PFBR will use plutonium-uranium oxide as fuel, and liquid sodium as coolant. If sodium comes into contact with water, it will catch fire. At Fukushima in Japan in March, four reactors' nuclear fuel core could not be cooled because the station suffered a black-out after the tsunami, which also knocked out the pumps and the diesel generator sets. So water could not be pumped for cooling the fuel core.)
As the PFBR boasted a number of redundancy systems and independent mechanisms, the reactor would be shut down with minimum problems in the case of any event, Dr. Baldev Raj told a news conference at Kalpakkam. It had nine control and safety rods, and three diverse safety rods which would help in shutting it down quickly.
S.C. Chetal, who took over as IGCAR Director, explained that in the case of sodium fire in an open place, sodium bicarbonate — a dry chemical powder — would be used to douse the fire. If sodium caught fire in an enclosed place, nitrogen would be injected to extinguish it. Sodium fire was milder than oil catching fire, Mr. Chetal said.
The floor level of all equipment related to the PFBR's emergency core cooling had been raised after the tsunami of December 2004 struck the PFBR's foundation pit, Dr. Baldev Raj said. Seismic activity all over the country was monitored from Kalpakkam round the clock. “We don't wait for the national alert,” he said. A tsunami protection wall had been built on the shore at the site and the township. Besides the PFBR, two Commercial Fast Breeder Reactors (CFBRs) of 500 MWe each would be built at Kalpakkam and their construction would begin in 2017. The layout of the two CFBRs was finalised and their site was getting readied.
Mr. Chetal said that while the 2004 tsunami wave had a height of 4.7 metres above the mean sea level (MSL) at Kalpakkam, the PFBR's floor level was 9.5 metres above the MSL. “There is no chance of sea water entering the PFBR buildings,” he added. The PFBR personnel had been trained in handling the combustible liquid sodium. There was no leakage of sodium for the past 14 years in the Fast Breeder Test Reactor (FBTR) at Kalpakkam, which was a forerunner to the PFBR. Although 75 kg of sodium was spilled in the FBTR prior to that, there was no fire, Mr. Chetal said.
Prabhat Kumar, Project Director, PFBR, said the total investment in the PFBR would be around Rs.560 crore. The cost of construction for a MWe was around Rs.11 crore. The cost was “naturally higher” compared to other electricity generating plants because all the PFBR equipment were manufactured for the first time in India. Electricity from the PFBR would be sold to State Electricity Boards at Rs.4.44 a unit. Mr. Kumar called the PFBR “a robust reactor” and various lessons learnt from the 2004 tsunami had been factored into its construction. The PFBR had a passive heat decay removal system.
Review of safety
After the Fukushima accident, two committees reviewed the safety at the Madras Atomic Power Station (MAPS) at Kalpakkam. Mobile power generation sets had been procured. According to K. Ramamurthy, MAPS Station Director, MAPS' emergency core cooling equipment was relocated to a higher level after the 2004 tsunami.
If power generating plants were set up on inland sites, thermal pollution would be more because the decay heat would have to be conducted into nearby water bodies, said P. Chellapandi, Director, Nuclear and Safety Group, IGCAR.