Note how BARC did the reactor design, the fuel design & even the plant design through various iterations. None of which would have been required if there was substantial Russian tech transfer for the design itself. Hence to state the program was "dead" without Russian assistance for the reactor and hull - disagree.
I'd in fact state the lack of available subsystems for submarines was a bigger challenge. How many non western suppliers could provide us or would work with us to provide us the various systems, raw materials and other items we required?
http://www.frontline.in/the-nation/crit ... 038061.ece
Building Arihant’s reactor was essentially a multidisciplinary effort that involved fuel development, thermal and mechanical engineering to manufacture the reactor pressure vessel, steam generators and high pressure components, control rod mechanism, control and instrumentation, electromechanical systems, drive mechanisms, and so on. “It is a marriage of all these systems to make the reactor work efficiently,” Banerjee said in August 2009. “It is not desktop research at all,” he emphasised.
BARC’s engineers and scientists were involved in all this, from engineering the concept to the final product development. For everything had to be developed from scratch and there was absolutely no technology available to India on the PWR.
While V.K. Mehra gave leadership to the reactor development programme and H.S. Kamat was in charge of fuel development, B.K. Bera, A.K. Suri and R.P. Singh played important roles on the fuel side. The contribution of G.P. Srivastava, M. Mahapatra and R.K. Patil was formidable in control and instrumentation. R.S. Yadav dealt with the design and manufacture of one of the most important components, the reactor pressure vessel. C.G. Utge was responsible for the development of high-pressure, high-temperature equipment.
Why was PWR, not Pressurised Heavy Water Reactor (PHWR) technology which India had mastered and used to build several commercial reactors, chosen to propel the submarine? PWRs use enriched uranium as fuel and light water as coolant and moderator. In contrast, PHWRs use natural uranium as fuel and heavy water as both coolant and moderator. “PHWR is not something which you can make into a compact form,” said Banerjee, who later became AEC Chairman. Besides, nuclear energy generation depends on the quantity of fissile material available in the reactor and the PWR lent itself admirably for this with a high availability of fissile material (uranium-235) in enriched uranium. While plutonium also can be used as fuel, enriched uranium-driven fuel is generally adopted for reactors that propel submarines.
The question now arose whether India had the capability to enrich uranium. (If the non-fissile U-238 is removed from natural uranium, then the U-235 concentration will go up. This is called enrichment of uranium. This is done by a series of chemical and physical processes. If one uses enriched uranium as fuel, the availability of neutrons is high enough to generate electricity and one can use light water as coolant and moderator.)
So a small plant was set up at Ratnahalli near Mysore in 1990 for enriching uranium, and work on designing the enriched uranium fuel for the submarine’s nuclear power pack also began. BARC made a technological breakthrough in developing all the centrifuges needed for enriching uranium without any external help. The centrifuges were needed to separate U-238 from U-235 so that the concentration of U-235 went up, but the separation technology itself was very complex. To sustain the centrifugal forces, centrifuges were to have a high strength-to-weight ratio. Yet, they had to be thin. So maraging steel was used in the manufacture of centrifuges.
The next step was to process the enriched uranium into fuel. Banerjee said: “This is also crucial because unlike in the case of fuel for the land-based reactor, here the fuel had to be monolithic. This required special fabrication techniques that allow you to make the fuel withstand the rolling, pitching and other movements of the submarine…. In Trombay, we developed the right kind of fuel.”
The reactor development itself was a big and tough task. At the heart of the reactor is its pressure vessel, which houses the fuel. Developing the pressure vessel entailed the use of a special technology and a special steel. The material had to have high fracture toughness and the toughness had to be retained even if the steel got exposed to radiation. So a special type of steel was developed to withstand the radiation environment.
The design of the vessel was another major challenge. The issue of the reactor’s compactness came in. The entire PWR had to fit into the cramped space of the submarine’s hull. Steam generators, tall structures consisting of a maze of pipes, posed another big problem. They produced steam to drive the turbine which generated electricity. So the steam generator and the pressure vessel were designed in such a way that every small space in the hull was made use of. This was a very important mechanical engineering design, which BARC engineers, after many trials and efforts, evolved.
Development of hundreds of subsystems and high-pressure valves and pumps posed various challenges, which were met by BARC engineers. Indian industry rose to the occasion by manufacturing them. The entire reactor structure had to be designed in such a way that it is stable when the submarine accelerates. What had to be taken into account here was that the reactor was housed in a submarine that sped under water. The thrust generated by the submarine’s propulsion required a design for the reactor that was different from that of a nuclear power reactor on terra firma.
“In designing the propulsion of the submarine, we had to take into account the various sea conditions, including rough sea, the submarine’s pitching and rolling, the effect of saline water, enemy action which includes underwater explosions/depth charges and internal conditions,” explained Basu. “Yet another factor is that the propulsion plant had to be compact and so weight and volume had to be minimised. Thirdly, the plant had to be very reliable. It is moving under water, hundreds of kilometres away from the shore. In case of an accident, no help will be available from outside. So back-up safety systems should function perfectly.”
So, the design of the safety system was crucial. BARC went for passive safety systems, which would not need an external source of electricity, to come into action. The passive thermo-siphoning system will come into play in abnormal conditions. Since a submarine’s reactor has no exclusion zone, unlike its counterpart on land where no human settlement is allowed a few kilometres around it, gamma shielding, and partly neutron shielding, by water was done.
In land-based reactors, control rods fall by gravity and bring the reactors to a halt in case of an accident. But the rolling and pitching of the boat demands that the control-rod mechanism is designed suitably to take care of the submarine’s various movements. “Since power has to be generated in a regulated manner, it puts a lot of restrictions on the design of the control mechanisms. Diverse techniques were used to design them. We had to take into consideration the possibility of the boat going upside down. So special sensors and drives were made for ensuring a safe and reliable operation of the control-rod mechanisms,” said Srivastava in August 2009. Indeed, 13 control mechanisms were accommodated within a diameter of 0.8 metre.
[BARC also built a simulator at Visakhapatnam to train navy personnel in operating the reactor. When the Russians were shown this simulator, they were amazed at its sophistication.
In the Arihant project, which went under the name of ATV programme, DRDO laboratories contributed sonars, sensors, sound absorption materials, communication equipment, electronics and weapons. While the Naval Physical and Oceanographic Laboratory (NPOL), Kochi, contributed sensors to Arihant, special acoustics were done by the Naval Science and Technology Laboratory (NSTL), Visakhapatnam.
In the end, as Banerjee emphasised, it boiled down to teamwork in a multidisciplinary project and he called the platform “a very complex combination of various technologies”. As Kakodkar said, “This PWR technology is very complex. You have to make it extremely compact and pack it in the cramped space of the submarine’s hull. It was a big challenge.”
Today, India can assert that it has mastered the technology of developing and manufacturing nuclear propulsion for driving submarines. The proof of it lies in three more nuclear-powered submarines being built at Visakhapatnam. When the four submarines, including Arihant, patrol the seas, India will have achieved the status of a blue-water navy.