Setting standards

The nuclear power project at Kudankulam features the latest in technology and takes safety to new levels even as work on its two units progresses way ahead of schedule.

T.S. SUBRAMANIAN in Kudankulam Photographs: A. Shaik Mohideen

EVERYTHING about the Kudankulam Nuclear Power Project (KKNPP) in coastal Tamil Nadu - the reactor buildings, the pumphouse, the pillars, the machinery and the cranes - is gigantic. The two reactor buildings will, on completion, stand 80 metres tall and 300 pillars will support each of the two turbine buildings. The core-catcher, an innovative bowl-like contraption, weighs 101 tonnes. The equipment is transported by sea from Russia to the mini-port that has been built at Kudankulam by erecting a dyke using 30 lakh tonnes of rock.

But size has not slowed things down, and the young workforce has gone on undaunted. The average age of the engineers is 36 and that of the workforce around 23. In two years since the first pour of concrete on March 31, 2002, signalling the start of construction, work on building the first unit (reactor) is six months ahead of schedule. In fact, the first reactor is on course to start generating electricity from March 2007, one full year ahead of schedule. Construction of the second unit is also coasting along.

`Kudankulam Nuclear Power Project: Setting Standards' is our motto, said KKNPP Project Director S.K. Agrawal. "We are setting standards. We are achieving excellence, too, at a low cost," he added.

Impressed with the speed of construction, the Government of India allotted an additional Rs.600 crores for the project for financial year 2003-04 - up from Rs.1,100 crores to Rs.1,700 crores. "This is a big indicator of how fast work is progressing," said S.K. Jain, Chairman and Managing Director of Nuclear Power Corporation of India Limited (NPCIL). "We are looking for Rs.2,000 crores" for 2004-05, he added.

The project involves the construction of two VVER-1000 Russian reactors at Kudankulam facing the sea in the Gulf of Mannar, 40 km from Nagercoil, in Radhapuram taluk in Tirunelveli district. Each reactor will generate 1,000 Mwe using enriched uranium as fuel and light water as both coolant and moderator. (VVER in Russian stands for voda, voda energy reactor. Voda in means water.)

NPCIL will execute all the gigantic civil and electrical work connected with the reactors. The Russian Federation will supply the reactor design, equipment and components such as the reactor pressure vessel, turbines, generators, nuclear steam supply systems and the core-catcher. These are now under manufacture in various industries in Russia.

Anil Kakodkar, Chairman of the Atomic Energy Commission (AEC) and Secretary, DAE, characterised the Kudankulam reactors as "an additionality to our domestic programme". He pointed out that the domestic nuclear electricity programme was entrenched in "the commercial domain" with the indigenous Pressurised Heavy Water Reactor (PHWR) technology having "matured".

The Kudankulam project has had a chequered history. On November 20, 1988, Prime Minister Rajiv Gandhi and Soviet President Mikhail Gorbachev signed an Inter-Governmental Agreement (IGA) for the construction of two VVER-1000 units at Kudankulam. It was to be a turnkey project - the Soviet Union providing the design, bringing in all the equipment and fuel and constructing the reactors too. The spent fuel was to be taken to the Soviet Union. But the project proved a non-starter because of the disintegration of the Soviet Union. Differences over the rouble-rupee payment ratio stalled the project further. In the early 1990s, the then AEC Chairman M.R. Srinivasan tried hard to revive it. Finally, it came alive with the signing of a supplementary agreement to the IGA in New Delhi on June 21, 1998, by Russian Minister for Atomic Energy Yevgeny Adamov and AEC Chairman and DAE Secretary Dr. R. Chidambaram.

The terms of the supplementary contract were radically different from those of the IGA. Under it, the Russians were to provide the reactor designs and supply the equipment. NPCIL would build the reactors. A team of Russian specialists would stay at the site to render technical assistance at all stages of construction, in the installation of reactor equipment and in the commissioning and operation of the reactors until the final takeover by NPCIL's operators. Russia would supply enriched uranium for the entire life of the reactors. This clause was a fallout of India's bitter experience with the United States vis-a-vis the two reactors it built at Tarapur - the U.S. terminated the agreement to supply enriched uranium fuel to the reactors. Unlike in the IGA, India would keep the spent fuel with it. The reactors would come under International Atomic Energy Agency (IAEA) safeguards; IAEA inspectors would visit the plant periodically to check whether there is diversion of fissile material for making bombs.

About thousand acres (400 hectares) of uninhabited and uncultivated land was acquired on the coast and the site is big enough to accommodate six reactors. Another 400 acres (160 ha) was acquired at Chettikulam, about 10 km away, for constructing residential quarters for NPCIL employees. Soon work on the project began under the stewardship of Vijay Kumar Chaturvedi, the then Chairman and Managing Director of NPCIL. (The Anu-Vijay township at Chettikulam is named after him.) The bhoomi puja was performed in October 2001 with Jain and Agrawal present.

Present at the first pour of concrete, on March 31, 2002, was a distinguished line-up of former AEC chairmen - M.R. Srinivasan, P.K. Iyengar, R. Chidambaram, Anil Kakodkar, V.K. Chaturvedi and S.K. Jain - besides the Russian delegation headed by E.A. Reshetnikov and the top brass of NPCIL.

NPCIL awarded four contracts in the form of mega-packages for project construction. The first package, for the construction of the reactor buildings of the two units, was awarded to Hindustan Construction Company Limited (HCCL). Simplex Concrete (Pile) Limited bagged the second contract, for the construction of the turbine buildings and safety-related structures. HCCL again won the contract for the construction of the breakwater dyke, sea water intake structures and the pumphouse. Larsen and Toubro won the contract for the fourth package, for constructing auxiliary buildings. Lee and Muirhead, Mumbai, has been entrusted with the transportation of all the equipment from Russia by sea to the mini-port. They have sub-contractors, Reshamsingh and Co.Private Limited, Mumbai, and Bertling, U.K., and have already ferried by ship the two core-catchers and other equipment.

ON March 12, the project site was bustling with activity, as a Frontline team found out. Masonry, welding, painting and grid-blasting were going on and tower-cranes were moving heavy equipment to place them in position. Machines were pouring concrete into seven-metre-tall pillars, excavators were digging up earth and pipelines were being laid.

The core-catcher has been installed in the reactor building of Unit 1. Said M.S. Suresh, Engineer-in-Charge (Reactor Building-1), KKNPP, NPCIL: "We placed it in position just three days back (March 9). It is made of steel and weighs 101 tonnes." It is held in place by massive nuts and bolts. Kanpur Engineering and Construction Company did the installation. In the case of a severe accident, the molten uranium fuel core from the reactor pressure vessel will fall into the core-catcher through a funnel and the radioactive fuel will remain there. It is so designed that the radioactive fuel will not fall on the floor of the reactor building and contaminate it. "The catcher is like a basket. (In case of a severe accident), it will hold the fuel life-long and the fuel will be cooled. The emergency core cooling system will be activated and the area around the core-catcher will be flooded with water.

In Reactor Building-1, construction of the 1.2-metre-thick inner containment wall was in progress. There will be an outer containment wall as well. This "dome within dome" will prevent radioactivity from escaping into the atmosphere. A pre-stressed cable passes horizontally through the innards of the reactor building's circular wall to prevent concrete from cracking.

Near the reactor building a tower crane is at work, moving heavy equipment into place. "The crane arrived from the Tarapur Atomic Power Project on 59 trailers and we assembled it here," revealed M.I. Joy, Site Planning Engineer, KKNPP. "It can be configured to different boom lengths. It can lift 800 tonnes of equipment at nine metres' length and 650 tonnes at 15 metres."

Some distance away from the reactor building is a fabrication shop for welding the liners - plates made of carbon-steel - that have arrived from Russia. Each plate is 9.1 metres long and 5.8 metres wide. Some are sized 13.2 metres by 5.8 metres. Each liner (plate) weighs seven to eight tonnes. The liners are "a critical component" that would be embedded on the inner containment wall, said E. Chinnaveeran, Engineer-in-Charge, Reactor and Nuclear Steam Supply System Erection. "These liners are used for the first time in our country. While the containment wall itself offers protection, the liner is an additional protection because stress and pressure requirements (in the reactor building) are high," said Chinnaveeran. The welded plates are subjected to ultrasonic resting and vacuum box testing for leak tightness.

According to R. Balachandran Mohan, executive (fabrication), HCCL, 14 liner segments are needed to make a circular ring and seven rings are required for lining the wall and the dome of each reactor. "We are embedding the steel plates into the concrete wall. The entire assembly will be designed and welded to form a cylindrical ring," he said. Liners are also used on the floor of the reactor building.

The turbine buildings to house the turbines and the generators are coming up fast and on completion will stretch 45 metres into the sky. Three hundred massive pillars of different sizes in the basement will support each turbine building, which is 94 metres long and 57 metres broad. "At 15.6 metres elevation (from the ground), we have the operating floor, where the turbines and generators will be erected," said S. Kalirajan, Engineer-in-Charge, Turbine Building-1. "Beyond 15.6 metres height, there will be no floors. Only external walls will go up." Two cranes would be installed permanently to handle the equipment during the installation and subsequent maintenance, Kalirajan added.

According to A.K. Kundu, assistant general manager, Simplex Concrete (Pile) Limited, and Debasis Sarcar, project manager, their company won the contract for Rs.142 crores for the construction of the turbine buildings, the diesel generator buildings, underground tunnels and the new fuel storage building. "We fill concrete to seven metres' height for pillars in one stretch so that the concrete does not lose quality," Kundu said.

The pumphouses, by themselves staggering in their dimensions, and their associated structures are called hydrotechnical structures. K. Majumdar, site-in-charge of HCCL for the pumphouse for the first unit, said the construction of hydrotechnical structures bagged by his company was the largest civil contract of NPCIL. The work order was valued at Rs.348.92 crores.

In a nuclear reactor, thermal energy (heat) is generated by nuclear fission reaction. This heat converts water into steam in the steam generators. This steam drives the turbine-generator to generate electricity, which is wheeled into the grid. The unused heat in the turbine (66 per cent of the total heat) is discharged in the condenser, which is cooled by a water system. This is called the condenser-cooling system. At Kudankulam, the cooling water will be drawn from the sea by pipelines. The water that has cooled the condenser is discharged back into the sea. While the sea water that will be sent in has a temperature of 32Celsius, the water discharged back into the sea will be hotter by five degrees. This is well within the Tamil Nadu Pollution Control Board's stipulated maximum difference of 7C aimed at protecting the fish population in the sea.

In fact, the fish protection facility at the project is unique. At the place where the intake concrete pipelines are laid on the seabed, compressors create an air-bubble curtain and waves on the ocean surface. So the fish will move up and float on the surface and not go down to enter the pipeline. These fish are then thrown out further into the sea by hydraulic ejectors. Said R.R. Kamath, Engineer-in-Charge, Hydrotechnical Structures: "Thus the system provides for the protection of fish species. This fish protection facility was qualified by an actual test in a small facility in Russia."

"Each unit (reactor) will need 2.5 lakh cubic metres of sea water an hour for cooling the condenser," said Kamath. The Gidroproekt Institute, a reputed Institute in Moscow, designed the cooling water system for Kudankulam after studying several variants, he said. The intake water will be taken 1.2 km from the shore by concrete pipelines laid on the seabed at a depth of 12 metres. This water will be brought to the pumphouse on the shore by gravity. Giant pumps will pump this water up to the condensers in the turbine buildings. After the condensers are cooled, the resultant water will be discharged at zero metres depth on the shore landfall itself so that it will travel some distance in the sea before it mixes with sea water. "Thus the mixing characteristics will be good (and there will be no harm to the fish)," said Kamath. An innovative feature of the cooling water system is the breakwater dyke built 300 metres from the shore. The dyke has two arms, each 900 metres long and 250 metres apart. The 300-metre gap from the shore is to ensure free flow of sedimentation so that the ecology is not affected. The intake water pipes are laid on the seabed below the dyke. The area set off by the dyke resembles a swimming pool. About 30 lakh tonnes of rock was dumped into the sea for constructing the dyke. Besides, 35,000 tetrapods, made of concrete and weighing five, 13 and 20 tonnes were cast at the project site and placed in the sea to create the dyke.

Agrawal explained that the dyke was meant to prevent the cool intake water and the hot discharged water from mixing in the sea. (Otherwise, the mixed hot water will enter the intake pipelines). Steel sheet piles have been hammered into the seabed for a distance of 500 metres on both the arms of the dyke to prevent the hot and cold water from mixing, said Kamath. A huge area of the sea was dewatered to enable the construction of the intake structures. The dewatered seabed still looks green. Joy said that 14 pumps, each of 100 horsepower, worked for three months to dewater the area.

The first unit of the project is expected to reach criticality in March 2007, in just five years from the first pour of concrete. Kudankulam is truly setting standards.