|Volume 20 - Issue 21, October 11 - 24, 2003|
T. S. SUBRAMANIAN
The construction of the Prototype Fast Breeder Reactor, a milestone on the road to energy security, begins at Kalpakkam in Tamil Nadu.
AS the 40-metre-tall tower crane's boom (arm) lifts up an L-shaped steel contraption called shutter, dangles it high in the air, and then lowers it on to a towering, half-finished pillar, two workers standing on a scaffold receive the shutter and bolt it to another around the pillar. The boom lifts up concrete in huge buckets and pours it into the hollow column of the pillar. Nearby, a worker is training jets of sand from a machine on big steel structures lying on the ground. In a few minutes, the rust on the structures is blasted away and they wear a gleaming grey look. Some distance away, excavators are dredging up earth on grounds as large as three football fields; earth has already been dug up to a depth of seven metres. This being a coastal site, just a few hundred metres away from the Bay of Bengal, water begins gushing out everywhere at a depth of 1.5 metres. Pumps are working round the clock, baling out 200 to 300 litres of water a minute.
Work is on in full swing on the construction of the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, about 70 km from Chennai, which will generate 500 MWe. The PFBR, a baby of the Indira Gandhi Centre for Atomic Research (IGCAR), is a milestone on the road to energy security for the country. The massive reactor, which will use plutonium-uranium oxide as fuel and liquid sodium as coolant, is expected to go critical in 2010. Its estimated cost is Rs.2,800 crores, and the actual cost when completed could be around Rs.3,492 crores. Building the PFBR is a technological challenge for the IGCAR because it involves a quantum jump from the currently operational Fast Breeder Test Reactor (FBTR) with a capacity of 13 MWe. The PFBR's construction heralds the beginning of the second stage of India's nuclear electricity programme, using breeder reactors. The first stage has already entered the commercial domain with 12 indigenously constructed Pressurised Heavy Water Reactors (PHWRs) generating electricity in various parts of the country. The PFBR is coming up just a few hundred metres away from the Madras Atomic Power Station (MAPS) at Kalpakkam, where two PHWRs are generating power.
ON August 18, the PFBR's bhoomi puja took place in the presence of Dr. Anil Kakodkar, Chairman, Atomic Energy Commission. Kakodkar said on the occasion: "We want to make a commercial success of this breeder technology. While we do that, we should keep in mind that this is not the end of the road. Based on this technology, we will build more reactors."
The IGCAR had started work on pre-project activities nearly two years ago and they are on the verge of completion. The administrative building is ready. S.B. Bhoje, IGCAR Director, said: " The PFBR construction involves complex high technology. The most important thing is that there is no hold-up in the manufacture of components (by the industries). We have to ensure timely inputs from research and development activities. We have already done good work on R&D, and the remaining will be done in six to eight months."
A tower crane putting in place a "shutter", in the course of the construction of a pillar for the shop.
Development of indigenous capability to manufacture special materials and critical components has been completed except for the grid plate, which will be over by December. Tenders have been floated for the manufacture of four main components: main vessel, safety vessel, inner vessel and steam generators.
A new company called "Bharatiya Nabhikiya Vidyut Nigam" - basically comprising people with managerial skills from the Nuclear Power Corporation of India Limited (NPC) and scientific and technological expertise from the IGCAR, the Bhabha Atomic Research Centre (Trombay), the Nuclear Fuel Complex and the Electronic Corporation of India (both Hyderabad) and the Heavy Water Board - will build the PFBR. Papers have already been filed for the registration of the company in Chennai. The company, which will start functioning by the end of October, will have full administrative and financial powers so that decisions will be taken quickly.
The advantages of having a new company are two-fold. First, it will not be a financial burden on the NPC, because during the period when the PFBR is constructed, there will be no revenue. Secondly, the IGCAR, a research and development organisation, is not equipped to execute a big project like the PFBR. Considering these factors, the Atomic Energy Commission suggested the establishment of a new company.
The nuclear electricity programme was established in India with the breeder cycle in mind. Dr. Homi Jehangir Bhabha, the father of India's nuclear power programme, unveiled a three-stage programme in 1955. In the first stage, PHWRs were built using natural uranium as fuel and heavy water as both coolant and moderator. There are 12 PHWRs operating in the country now. The NPC is building six more PHWRs - two each at Tarapur, Kaiga in Karnataka and Rawatbhatta in Rajasthan - and two Russian light water reactors at Koodangulam in Tamil Nadu.
At the Structural Mechanics Laboratory, a model of the main vessel of the PFBR, one-tenth the size of the original, on a shake-table, as part of a seismic experiment.
The second stage envisages the construction of Fast Breeder Reactors, which will use plutonium reprocessed from the spent fuel of the PHWRs and their depleted uranium. They are called breeders because they breed more fuel than they consume. Plutonium breeding allows them to extract 60 to 80 times more energy from uranium than thermal reactors such as the PHWRs. This makes breeders economical for countries like India which have scanty uranium reserves.
In the third stage, the vast thorium reserves available in the country will be used to generate electricity.
The first step towards the construction of breeder reactors was taken when the Fast Breeder Test Reactor (FBTR) at Kalpakkam attained criticality in October 1985. It marked the culmination of 10 years of dedicated work to master a complex technology. The FBTR used plutonium-uranium mixed carbide as fuel for the first time in the world. It has a total capacity of 40 MWt (13 Mwe). Although during the first several years, the FBTR was plagued by problems, it has now stabilised. Connected to the southern electricity grid in July 1997, the FBTR has been operating at a capacity of 17.4 MWt since March 2002.
In fact, as on September 26, the FBTR had operated for 65 days almost continuously except for a couple of brief shutdowns. The fuel has reached a burn-up of 1,10,000 MWd/t (megawatt days per tone) without any failure. The FBTR's critical components such as the control rod drive mechanism, the intermediate heat exchanger, the sodium pumps and the steam generator are operating well.
Given the hands-on experience in operating the FBTR, Bhoje is confident about handling the huge scale-up from the FBTR's 13 MWe to the PFBR's 500 MWe. "The PFBR entails complex high technology. We are prepared to take up this challenge," he said.
The steel structures that will support the site assembly shop's roof undergo sandblasting, an anti-corrosion measure which is necessary as the project comes up close to the sea.
BACK at the site, scores of workers are engaged in the construction of the 180-metre-long and 23-metre-tall site assembly shop (SAS), which is to be ready by January 2004. If big-sized components, needed for the turbine, the steam generator and so on, are assembled here, even bigger components will be integrated in a 34-metre-tall high bay.
Sandblasting of the steel structures, which will support the roofs of the SAS and the high bay, was under way as an anti-corrosion measure. The structures are also given two coats of synthetic enamel paint. "Rust is a real cancer. This place is hardly a couple of hundred metres away from the seashore. We are ensuring quality from all angles," said D. Ravindran, Civil Engineer, PFBR, Department of Atomic Energy (DAE).
At the site, there are boards emphasising the importance of safety. All workers wear helmets and those working at heights are in harnesses. G.V.V.S.R. Kishore, Civil Engineer, PFBR, said: "Every week we conduct safety classes for the workers to prevent accidents."
Excavation work is on for what is called the nuclear island, which will comprise about 10 huge buildings including the reactor building. The turbine building will come up separately under the power island. S.R. Jayaraman, consultant to civil works, PFBR, said: "Between August 18 and September 26, we excavated earth over an area of 250 m by 225 m, and up to a depth of 7 m. The draft (foundation) will go to a depth of 17 to 18 m. All the nine or ten buildings will come up on the same draft."
Since water gushes out at a depth of 1.5 m itself, machines are at work round the clock pumping it out. The water is let into a channel that leads to a reservoir and used for industrial purposes. "If you had come here last week, you would have seen that it looked like a flooded area. Now it is dry like a football field. If we stop pumping, the water level will rise again," said Jayaraman.
S.B. Bhoje, Director, Indira Gandhi Centre for Atomic Research.
Besides the challenges in civil engineering, those in manufacturing technology are also being met. They include the development of huge sodium pumps, steam generators, nuclear steam supply systems, the control and safety rod drive mechanism and reprocessing technology. Engineers of the IGCAR designed the steam generator and BHEL, Tiruchi, built it. The steam generator tube, which is 26 m long and 1.24 m in diameter, is entirely steamless. Its fabrication by the Nuclear Fuel Complex was an important achievement. While liquid sodium circulates in the outer pipe in the steam generator, water at high pressure circulates in the tubes inside. The sodium coolant, driven through the reactor core by pumps, gets heated to a high temperature owing to the fission in the reactor. This heat is transferred to the water, which becomes steam and drives the turbine, generating electricity.
The fabrication of the main vessel, which contains primary sodium, was another big challenge. It has a height and a diameter of 13 m each. It is made of stainless steel of thickness varying from 25 mm to 40 mm and can hold 1,150 tonnes of liquid sodium.
At the Structural Mechanics Laboratory, a model of the main vessel, one-tenth the size of the original, sits on a shake-table. Instead of liquid sodium, the vessel has water. As the table shakes violently to simulate an earthquake, water sloshes out of the vessel. In-depth analyses are made to find out whether the vessel is displaced, has undergone strains, developed cracks or suffered fatigue owing to the "earthquake".
Dr. P. Chellapandi, head of the Mechanics and Hydraulics Division, IGCAR, said: "This shake-table is a unique facility in the IGCAR by which the seismic integrity of reactor assembly components is ensured in all respects. The seismic integrity of the PFBR's critical components has been tested for the past 20 years. A team has been working exclusively on this for the past 20 years." The shake-table cost Rs.5 crores.
A little away, a full-scale, large-sized pipe bend was being shaken up to see whether it suffered metal fatigue. According to Chellapandi, industries manufactured the PFBR components, which were large-sized and were of a special nature. Each component was tested many times under real, normal and abnormal seismic conditions in the Structural Mechanics Laboratory.
Bhoje asserted that India was right in going for breeder reactors. While 40 per cent of the homesteads in the country use kerosene as fuel, another 50 per cent use firewood for cooking. The country has only a limited amount of coal for generating electricity; hydel resources too are inadequate. So, according to Bhoje, the option lies with nuclear power. With about 60,000 tonnes of natural uranium available in the country, which will last only 30 years, about 12,000 MWe can be generated by setting up PHWRs. However, if the uranium-238 isotope of natural uranium is converted into plutonium and used as fuel in breeder reactors, about four lakh MWe can be generated for a long time. "That is why we are justified in going for breeder reactors," Bhoje said.
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