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Countdown begins

Print edition : Aug 14, 2009 T+T-
The reactor buildings of Units 1 and 2.-A. SHAIKMOHIDEEN

The reactor buildings of Units 1 and 2.-A. SHAIKMOHIDEEN

WE are now standing on the sea, declared S. Venkatesh, Senior Commissioning Engineer, Kudankulam Nuclear Power Project (KKNPP), as we looked around bewildered and found that we were indeed standing on several acres of concrete platform built 500 metres into the sea.

The wind from the Gulf of Mannar was gusting around us, and below us, a big reservoir of sea water, called breakwater dyke, had been built. Another 700 m into the sea were four caissons, massive concrete structures, that had been placed in specially designed beds at the mouth of the breakwater dyke. The caissons two of them weighing 2,900 tonnes each and the other two weighing 2,400 tonnes each have big gates to allow the smooth flow of sea water to cool the condensers in the two reactors of the KKNPP.

Ahead of us, on the shore, rose the two domed reactor buildings of the KKNPP, each 80 m tall. There is an array of buildings around: the 45-m-tall turbine buildings, the massive pump-houses, the big desalination plant, the demineralisation plant, the building that houses the ready-to-use enriched uranium fuel bundles, and so on. Everything about the KKNPP is gigantic.

With the project nearing completion, things are on course for the commissioning of the first unit of the KKNPP in the first quarter of 2010. Pre-commissioning activities for starting the first reactor are in full swing and all is set for the loading of the dummy fuel into the reactor in August/September. Then the commissioning activities will begin and the reactor will be made ready for the loading of the real fuel by November/December 2009. S.K. Jain, Chairperson and Managing Director, Nuclear Power Corporation of India Limited (NPCIL), said, We are preparing the reactor for the ultimate milestone of the loading of fuel and the start of criticality. We are confident that Unit-1 will start generating power early next year.

The KKNPP involves the construction of two Russian VVER-1000-type reactors at Kudankulam in Tirunelveli district in Tamil Nadu. Each reactor will generate 1,000 MWe of power. The fuel will be enriched uranium. Light water will be both coolant and moderator. Hence, the occurrence of the word voda two times in VVER, which in Russian stands for voda, voda, energy reactor. Voda means water. In simple terms, they are called light water reactors (LWRs). Atomstroyexport, the Russian nuclear monopoly, has provided the designs and supplied all the equipment and components for the two reactors. According to Jain, the Russian Federation has given a binding commitment for the supply of enriched uranium fuel for the lifetime of the two reactors.

While the Russian Federation provided the reactors design and supplied all the equipment and components, NPCIL executed all the gigantic civil construction and mechanical erection of the two reactors. It will also commission and operate the plant.

K.C. Purohit, Project Director, KKNPP, stressed how NPCIL had to contend with a totally new technology in building these two Russian LWRs. For NPCIL had hitherto built only the indigenous Pressurised Heavy Water Reactors (PHWRs), which use natural uranium as fuel and heavy water as both coolant and moderator.

Purohit said: We have come to a stage where most of the construction and erection work is over. We have started the pre-commissioning activities and some commissioning work. The challenges involved in the construction, erection and commissioning responsibilities have given us a whole insight into this new technology.

He listed the major milestones that the project had crossed in the work on Unit-1. The construction of the dome-shaped reactor building is complete. It is a dome within a dome. The inner containment dome has a wall 1.2 m thick and its inside has a steel lining, 6 mm thick. The outer containment dome has a thickness of 60 cm. The domes are to prevent radioactivity from leaking into the atmosphere in the extreme possibility of an accident.

Work on erecting the passive heat removal system (PHRS) is complete. It is the first time that any reactor in the world will use this system. If no cooling mechanism is available in case of an emergency, the PHRS will allow the air from the atmosphere to enter the reactor building and cool the reactor.

Other milestones include the erection of huge equipment such as the reactor pressure vessel (RPV), the steam generator, heat exchangers and the core-catcher. The RPV is a huge receptacle that houses the enriched uranium fuel assemblies. It is a 359-tonne contraption made of stainless steel. The vessel itself is kept inside a one-metre-thick concrete vault.

A.K. Pal, Chief Construction Engineer, KKNPP, said: The installation of such a heavy mass, with an alignment of one mm accuracy, is a great achievement because it had to be brought inside horizontally, lifted slowly with special tools and tackles so that it did not swing, positioned vertically and kept on a metallic ring. It was so tough doing all this. Yet another milestone is assembling the fuelling machine, a huge robot. It has been energised too. The fuelling machine will insert the enriched uranium fuel assemblies into the reactor core and also remove the spent fuel assemblies.

Another civil engineering marvel is the construction of a 19-m-deep pond, which will store the spent fuel assemblies from the reactor. It is made of concrete and lined with steel and carbon steel to prevent water from leaking. The erection of the main coolant piping has been completed for both the units. Pal called it a pioneering job because 32 coolant pipe pieces, each weighing about 12 tonnes and with a diameter of 85 cm, had to be welded with precision.

The turbine building houses the turbine and the generator. The turbine generator is ready to receive steam, which will rotate the turbine and generate electricity.

A desalination plant with four units has started operation. Each unit will produce 1,06,000 litres of water an hour. The demineralisation (DM) plant, where pure water will be obtained, is nearby. This pure water will be used as primary and secondary coolant in the reactor.

NPCIL awarded four contracts in the form of mega packages for project construction. Lee & Muirhead Private Limited, Mumbai, was entrusted with the transportation of all equipment from Russia by sea to Kudankulam. Pankaj Gadhia, chief executive officer, Lee & Muirhead, said the company, acquired by the Parikh family in 1945, had come a long way from being a small Custom House clearing agent to a diversified logistics company handling about one million freight tonnes of project cargo every year across India for industries.

Pankaj Gadhia added, Over the past 64 years, the company has established new ventures, including joint ventures with global partners such as Deutsche Post and DHL. Today, Lee & Muirheads core strength is in handling large industrial projects on a door-to-door basis. NPCILs Kudankulam project, which involved 4,00,000 freight tonnes provided a challenge to the group.

The company has handled project materials for several power projects. It is also focussing on petroleum and refineries, chemical and steel sectors. NPCIL, while focussing on the construction of the two units, also developed the human resource needed for operating and maintaining the reactors. It chose people who were experienced in the commissioning and operation of the indigenous PHWRs and the two LWRs (built at Tarapur, Maharashtra, by General Electric of the United States). NPCIL top brass developed with their Russian counterparts a blueprint for the training of Indian personnel to commission, operate and maintain the two VVERs.

A three-phased programme was prepared, with the second part implemented in the Russian Federation.

The understanding was that our personnel will be tested and examined by Russian specialists. I am happy to say that all our colleagues did very well in the examinations held in Russia, said Purohit.

The programme had already produced about 60 graduate engineers needed for operating and maintaining the two reactors.

M.K. Balaji, Chief Superintendent, KKNPP, who heads the group of engineers who will commission and operate the two reactors, said the team had started the commissioning activities for Unit-1.

We initially need power supply from the Tamil Nadu grid and the chilled water system before we go to the next stage of commissioning the reactor, he said.

The plant was drawing electricity from the State grid from November 14, 2008. The desalination plant will meet the water requirements of the plant, said Balaji, as he proudly held a bottle with water that was collected from the desalination plant on February 21, when it was commissioned.

The pre-commissioning activities of the reactor have started, said Balaji. These activities included filling the pond inside the reactor building.

After a year of reactor operation, the fuelling machine will remove one-third of the spent fuel assemblies from the reactor core and position them inside the fuel racks in the pond, which is already filled with water.

To ensure total safety, we are checking the integrity of the pond so that water does not leak out of it, he added. Another pre-commissioning activity involves flushing the reactor coolant pipes with water to exclude foreign material. Water will be pumped into various circuits and it will be flushed towards the reactor as part of an open-loop flushing (that is, the reactor will be kept open).

R.S. Sundar, Technical Services Superintendent, KKNPP, said, This is a major pre-requisite before we start further commissioning activities of the reactor, such as loading the dummy fuel assemblies and the hot run. We are now in the stage of filling the spent-fuel pond with water and the next operation will be open-loop flushing. An entire group is working on these. In the hot run, hot water is circulated through the entire circuit so that the systems performance is established. A magnetite liner was created on the inside of the pipes made of carbon steel as an anti-corrosion measure.

Cabling is under way in the state-of-the-art control room for Unit-1, which is akin to an aircrafts cockpit. M.I. Joy, Additional Chief Engineer (Site Planning), KKNPP, said, Once the cabling is completed, the entire control of the plant, including the reactor and turbine, will be done from the control room.

The plants control room is humidity-controlled. The atmosphere is so pure here that the cables will not be spoiled, said Joy.

The dummy fuel has the same weight and dimensions of the real fuel. In all, 163 dummy fuel assemblies will be loaded in September into the reactor core and the core will be brought to the status of hot operation.

The conditions in which the reactor will operate will be simulated. This will signal the start of the commissioning activities. The reactor control systems will be tested and the real fuel assemblies loaded into the reactor core. The reactor will then reach criticality.

After criticality, NPCIL personnel will perform low-power physics experiments using the reactor and slowly increase the power output. Finally, electricity generated from the reactor will flow into the grid.