In the presence of Atomic Energy Commission (aec) chairman Anil Kakodkar and India's distinguished nuclear scientists and personnel who had made this possible, Unit 3 of the 540 mw Tarapur Atomic Power Station (taps) attained criticality (nuclear parlance for an atomic plant becoming operational), with the start of a self-sustaining nuclear fission chain reaction in the reactor core. "This is a great achievement," exulted Kakodkar. "It has exceeded even the copy book criticality reached by taps-4 on 6 March 2005 and underscores the maturity reached by India's nuclear establishment." According to him, this vital event has rendered the country's slope of growth in nuclear power even steeper. Shreyans Kumar Jain, chairman of the state-owned Nuclear Power Corp. of India Ltd (npcil), which builds and operates the country's atomic power stations, added, "India has shown once again that it has developed total comprehensive capabilities in the entire spectrum of nuclear power generation, from design to project implementation and management." Both Kakodkar and Jain are confident that the Pressurised Heavy Water Reactors (phwrs) of taps, located at Maharashtra's coastal town of Tarapur, 130 km north of Mumbai, and the other units proposed and under construction will help reach the targeted 20,000 mw of nuclear power by 2020 and 40,000 mw by 2030. taps-3 will be India's 14th phwr in operation, with Tarapur being the site for the country's first commercial nuclear reactors - taps 1 and 2 - which are Boiling Water Reactors (bwrs), currently operating at a derated capacity of 160 mw each. Both these had become commercially active in October 1969 at their original output of 220 mw. phwrs use natural uranium fuel and heavy water both as moderate and coolant, while bwrs are fuelled by imported low enriched uranium (leu). With the 540 mw taps-4, which commenced commercial operation from 12 September 2005, generating 483 mw of electricity at present, the overall nuclear power output in India has edged to 3,273 mw. This constitutes 2.66 per cent of the current national electricity output of 123,014 mw. taps-3, which is scheduled to be synchronised with the grid a month from attaining criticality and to become commercial another month later - that is, by the third week of July - will function at a derated output initially, until it gradually revs up to full capacity. According to A.M. Desnavi, technical services superintendent and commissioning chief of taps-3, unit 4 came to be commissioned before unit 3 simply because the bedrock at its adjoining site for laying the foundation was reached earlier. Jain points out that the construction of both taps 3 and 4 was completed 7 months ahead of schedule. "Besides, some deft value engineering, government permission for a downward revision of the equity cost and improved construction management helped contain the overall cost of the two reactors to Rs6,100 crore from the approved cost of Rs6,525 crore," he observes. "The original estimate had, in fact, been Rs8,000 crore." Installation costs hence work out to Rs5.65 per megawatt electrical (Mwe), which Jain terms as "around the best internationally" for non-hydel power. "Strenuous efforts are being made worldwide to peg the costs to this level," he claims. While electricity from the older taps 1 and 2 is supplied at Rel per unit, that from taps 3 and 4 will cost Rs4.25 at present. "We are, however, confident of bringing this down to Rs2.50 or even lower than the current notified tariff of Rs2.65 per unit," mentions Kakodkar. Power from these units will be supplied to Maharashtra, Gujarat, Goa and Chhattisgarh, though power-starved Maharashtra receives 50 per cent - or 160 mw - from taps 1 and 2 and 39.81 per cent - 430 mw - from the two larger reactors. Jain indicates that npcil has successfully upgraded the 540 mw design into phwrs of 700 mw, which will cost only marginally more and will thus render nuclear power even more competitive. Eight 700 mw units have been initially proposed, two of which will be located at Rawatbhata in Rajasthan and two at Kakrapar in Gujarat, the sites for the remaining four yet to be identified. npcil has plans to enhance the installed nuclear power capacity to 4,120 mw by the end of the 10th Five Year Plan (2002-07) and to 10,280 mw by the end of the 11th (2007-12).