Finally, the wait is over. The design of World's first Thorium based nuclear reactor is ready.India Today Online brings you the first look of design and prototype of the Advanced Heavy Water Reactor, also termed as AHWR.It is the latest Indian design for a next-generation nuclear reactor that will burn thorium as its fuel ore.The design is being developed at Bhabha Atomic Research Centre (BARC), in Mumbai, India and aims to meet the objectives of using thorium fuel cycles for commercial power generation.The AHWR is a vertical pressure tube type reactor cooled by boiling light water under natural circulation. The unique feature of this design is a large tank of water on top of the primary containment of vessel, called the gravity-driven water pool (GDWP). This reservoir is designed to perform several passive safety functions.Dr R K Sinha, chairman, Atomic Energy Commission, in an exclusive interview to India Today Online said, "This reactor could function without an operator for 120 days."The AHWR is a unit that will be fueled by a mix of uranium-233 and plutonium - which will be converted from thorium by previously deployed and domestically designed fast breeder reactors.Thorium is an element that is three times more abundant globally than uranium. As all mined thorium is potentially usable to breed reactor fuel. India's abundant reserves of thorium, constitute 25 per cent of the world's total reserves.Earlier, India produced the world's first thorium nuclear reactor, the Kakrapar-1, in 1993, and as part of India's three-stage fuel cycle plan, a new Advanced Heavy Water Reactor (AHWR) is being designed, slated for operation in 2016. The country hopes to use thorium-based reactors to meet 30 per cent of its electricity demands by 2050.The AHWR is slated to form the third stage in India's three-stag fuel-cycle plan. It is supposed to be built starting with a 300 MW prototype in 2016. Later, the first megawatt of electricity would be be generated by 2025. "To generate a single megawatt of electricity from this world's first thorium based reactor it would take at least 7-8 years," said Dr Sinha.Dr Sinha said, "This will reduce our dependence on fossil fuels, mostly imported, and will be a major contribution to global efforts to combat climate change."It is also said to be the most secured and safest reactor, which in future, could be set up in populated cities, like - Mumbai or Delhi, "within the city".The latest AHWR design incorporates several passive safety features. These include: Core heat removal through natural circulation; direct injection of emergency core coolant system (ECCS) water in fuel; and the availability of a large inventory of borated water in overhead gravity-driven water pool (GDWP) to facilitate sustenance of core decay heat removal. The emergency core cooling system (ECCS) injection and containment cooling can act (SCRAM) without invoking any active systems or operator action.The reactor also incorporates advanced technologies, together with several proven positive features of Indian pressurised heavy water reactors (PHWRs). These features include pressure tube type design, low pressure moderator, on-power refueling, diverse fast acting shut-down systems, and availability of a large low temperature heat sink around the reactor core.The construction on the first AHWR is scheduled to start in 2016 - though no site has yet been announced. Sources says, "nothing has decided, it could be Tarapur in Mumbai or some other location in India".