The journey from RAPS-1 in Rajasthan to Kaiga-4 in Karnataka has encompassed sequential improvement in reactor design – in operational working, safety features, and per unit costs – making India a global front runner in pressurized heavy water reactor (PHWR) design. In the process, the excellence in Indian design PHWRs was highlighted by Kakrapar 1 and 2 reactors being declared (in 1994-1995) as the best PHWRs in operation world over.

Having mastered 220MWe capacity PHW reactor design, with as many as 16 such PHW nuclear power reactors in operation, the Indian nuclear establishment has successfully upgraded reactor capacity to 540 MWe, embodied in Tarapur 3 and 4 reactors, now running at availability factor of 92 to 95 per cent for the last three to four years. Further on, the next round of indigenous PHWR design has been upgraded to 700 MWe capacity reactors. As many as 10 such 700 MWe pressurized heavy water reactors are being lined up for construction.

Construction of Kakrapar 3 and 4 and Rajasthan 7 and 8 PHWRs of 700 MWe capacity is already in full swing. Construction of six more such reactors is being processed – four at Kumharia in Haryana and two at Bargi in Madhya Pradesh. Construction of a further six to eight 700 MWe indigenous design PHWRs at Markandi in Orissa awaits the Centre’s clearance.

Mastering PHWR design capability has, however, been achieved through the hard road of indigenous technology development over three decades – a road of scintillating achievements, hardly equaled anywhere. It entailed indigenous mastering of several key fuel cycle technologies and building equipment and infra structure industries, a tough challenge by any standard.

What are these key technologies, mastering of which is a prerequisite for capability to build nuclear power reactors? To quote a leading nuclear scientist, “The first group of these technologies relates to basic disciplines needed for design of the reactor, such as reactor physics, structural design of reactor systems, core thermal hydraulics, and reactor control and instrumentation. In each one of these areas the challenges lie … in the development of computer codes, determination of physical properties relevant for full understanding of component behaviour, experimental validation, and testing under simulation of actual conditions. (After acquiring a grip on these technologies), one is able to design, develop and upgrade any reactor system.”

Paving the way for pressurized heavy water reactor design construction is just a half-way journey. The PHWR power generation programme requires several other major inputs, all of which pose searing challenges. These major inputs are: appropriate nuclear fuel development, building heavy water plants, and nuclear electronic instrumentation.

A telescopic view shows monumental achievements in all these inputs by the India’s nuclear establishment. Building the Nuclear Fuel Complex (NFC) at Hyderabad is a monumental achievement. The NFC tackles the challenges in providing appropriate nuclear fuel on an ever enlarging scale – not only for the bulk of the reactors of PHWR design, but also for the Tarapur 1 and 2 reactors using enriched uranium fuel. En route, NFC has, in delivering nuclear fuel that matches perfection standards required of nuclear operations, done intensive research to produce the unique zirconium alloy cladding for fuel bundles of PHWR design requirement. Zirconium alloy produced by NFC is also valuable for manufacture of critical PHWR coolant channel components, and other reactor internal structures.

Building heavy water plants for India’s PHWR programme has been an all-round success story – beginning from a low base, projecting India into world leadership in heavy water, both in terms of quantity, quality and price. The challenge of electronic instrumentation has been adequately met by the Electronic Corporation of India (ECIL).

It would be an understatement to be content with lauding these fantastic achievements. More such prowess is needed for continuing operation of the chain of power reactors – developing capability for life management of operating reactors. This is a challenging task involving R&D effort in areas like inspection techniques, analytical methodologies and computer codes for assessment of integrity of components, on-line monitoring and diagnostics. Technologies have to be developed for repair, maintenance and replacement. Most of the critical components operate in high radiation environment, which adds a new dimension to the study of their ageing behaviour.

That the challenge of life management of the chain of reactors has been met with great capability is demonstrated in tackling the operation of ageing Tarapur 1 and 2, functioning at high capacity factors beyond their life time. And delivering electricity to the Maharashtra electricity grid at the lowest charge per unit electricity.

Dr Homi Bhabha’s three-phase nuclear programme envisages construction of PHWR design in the first phase, using plutonium obtained from reprocessing reactor spent fuel for Fast Breeder reactors in the second phase, and building next generation reactors using thorium as the nuclear fuel to launch the third phase. Kaiga-4, along with Kaiga-3 and RAPPS 5 & 6, denotes a high-end achievement of the first phase of this nuclear quest. The second phase has been launched with the 500 MW prototype Fast Breeder Reactor being successfully constructed at Kalpakkam. Basic fast breeder technologies have been acquired with construction of Fast Breeder Test Reactor (FBTR), operating successfully for twenty-five years, using indigenous design plutonium-uranium mixed fuel.

The third phase of the Bhabha-ordained programme has also been initiated by developing appropriate fuel – Uranium 233 – produced by irradiation of thorium by placing thorium as blankets in operating fast breeder reactors. The unique next generation design Advanced Heavy Water Reactor developed at BARC provides a short-cut to the third phase – the thorium phase.

These multi-fold advances in nuclear technology have meant India’s emergence as an advanced nuclear capability nation on the global arena. India has now to project itself as a nuclear exporter – not only in heavy water and radio isotopes for medical use, as of now, but also in PHWRs. With the aura of global nuclear renaissance spreading, India can look forward to provide reliable and sturdy 220 MWe and 540 MWe PHWRs to friendly developing countries under IAEA safeguards. (IPA Service)