TAPS at thirty

The Tarapur Atomic Power Station, India's first nuclear power project, celebrates the 30th anniversary of its commercial operation.

THE Tarapur Atomic Power Station (TAPS), which was set up to demonstrate that nuclear power stations can make commercial sense in India, has completed 30 years of its operation. The flagship of the country's nuclear power programme, as Atomic Energy Commission Chairman Dr. Anil Kakodkar refers to it, started work with two Boiling Water Reactors (BWRs) built by General Electric of the United States on a turn-key basis.

The 30 years were full of challenges. There were cases of theft of equipment and of denial of technology when problems arose with the reactors' components. The U.S. went back on the agreement to supply enriched uranium fuel. Corrosion affected the sea water circulation system. Tubes in the secondary steam generators developed cracks.

V.K. Chaturvedi, Chairman, Nuclear Power Corporation (NPC), pointed out that while the U.S. and Germany had shut down BWRs that were 30 years old, the units at TAPS were going strong. "We are confident that we will be able to operate them for another 30 years," he said.

T.C. Upadhyay, Senior Technical Manager, TAPS, described the 30th anniversary celebration as ''the reunion of the past and the present''. He said: "In the past 30 years, we have had our moments of despair and occasions of joy. We managed to overcome many obstacles."

According to Kakodkar, TAPS is still on the ascending curve because of its continuous upgradation and the regular monitoring of its performance. The two units have undergone 300 modifications so far, a testimony to the ingenuity of India's nuclear engineers. "On the basis of this immensely successful experiment, we are making great strides in our nuclear power programme," Kakodkar said.

The station's performance in 2000 was exemplary: the second unit ran continuously for 209 days; both the units notched up a capacity factor of 86 per cent, the highest for a year since the station began commercial operations in 1969; and the total commercial generation was 2,418.61 million units, also the highest since 1969.

At the 30th anniversary celebrations of the Tarapur Atomic Power Station, (from left) V.K. Chaturvedi, Chairman and Managing Director, National Power Corporation; A.P.J. Abdul Kalam, Principal Scientific Adviser to the Government of India; R.C. Rawal, Project Director, TAPP 3 and 4; and Anil Kakodkar, Chairman, Atomic Energy Commission.

Reactor tripping and long outages are a thing of the past. According to S.C. Katiyar, Station Director, TAPS 1 and 2, the plant personnel created a record by completing the refuelling outage of the first unit in just 41 days against the normal duration of 100 days. The first unit was shut down for refuelling on June 8, 2001 and was started up on July 18. Katiyar said that this record compared very well with international standards. During those 41 days, the plant engineers, besides replacing the fuel inspected the core shroud, overhauled the turbine, replaced the piping for circulating water, changed the tube for the emergency condenser, overhauled the reserve pumps, and reconditioned a number of valves and relief valves.

P.M. Wagh, Director, Health and Safety, NPC, said the station had gone from strength to strength because "from the beginning, we took it as a challenge to run the two units". The station engineers were undaunted when the tubes in the secondary steam generators developed cracks and the sea water circulation system was corroded. Wagh said that while elsewhere in the world there were reports of cracks appearing in the core shroud of some BWRs the reactor shroud at TAPs had not shown any stress. (The shroud is a cylindrical shell, one inch thick, that surrounds the core.)

Wagh said the total cost of the plant (Rs.96 crores) had been recovered and that the history of the plant proved that nuclear power was safe, reliable and environmentally benign.

The book Atomic Energy in India, 50 years, written by C.V. Sundaram, L.V. Krishnan and T.S. Iyengar and published by the Department of Atomic Energy (DAE) in August 1998, gives a short, insightful history of TAPS. It says: "In July 1954, a month before the DAE was set up, (Homi J.) Bhabha wrote to (Prime Minister Jawaharlal) Nehru outlining his vision for a comprehensive atomic energy programme in India. It included power reactors to generate electricity as well as plutonium, another type of power reactors to breed plutonium and even special reactors for the propulsion of naval craft." Bhabha held discussions with top officials of the United Kingdom, the Soviet Union and the U.S. Soon plans were under way for building the first nuclear power project in the country. The idea was to train Indian engineers and scientists in building such projects.

The choice of Tarapur, about 100 km from Mumbai, to locate the project was announced in August 1960. In October 1960, global tenders were invited for constructing two nuclear reactors. The government decided to go in for BWRs, which use enriched uranium as fuel and light water as both coolant and moderator. In BWRs, water is allowed to boil to generate steam in the reactor vessel itself. On May 8, 1964, a contract for the construction of two BWRs at Tarapur was signed in the U.S. under an agreement for cooperation between the governments of India and the U.S. It was a turn-key project, and Bechtel was the architect-engineers.

The construction began in October 1964. The first unit went critical on February 1, 1969 and it was connected to the grid on April 1, 1969. The second unit reached criticality on February 27, 1969 and power from it was wheeled into the grid on May 18, 1969. They were declared commercial on October 1, 1969, and were dedicated to the nation by Prime Minister Indira Gandhi.

The book says: "At the peak of construction, about 6,500 were at work at the site. The Americans numbered about 120. With M.R. Srinivasan as the Principal Project Engineer, the Indian personnel participated fully at different stages like drawing up specifications, reviewing the design and offering suggestions for improvement, supervising erection, testing and commissioning of systems. The project afforded an opportunity for the Indian engineering community to become familiar with some of the new techniques used in the construction activity quite apart from the novelty associated with the nuclear technology."

The project ran into several problems initially. During the India-Pakistan war of 1965, a ship carrying two steam generators for the project was stuck at the Karachi port and the consignment could never be traced. General Electric brought in replacements six months later. Problems continued even after the station began commercial operation. The U.S., which was to supply enriched uranium for 30 years under an agreement, stopped the supply after India conducted its peaceful nuclear experiment (PNE) at Pokhran in May 1974. France stepped in to supply fuel for 10 years. The supply stopped in 1992. India received enriched uranium from China under a commercial contract. Meanwhile, India developed mixed oxide (MOX), a mixture of uranium and plutonium, which partly replaced enriched uranium. The MOX fuel, which was inserted in both the reactors, has given several successful cycles.

Dr. Kakodkar said that China would continue to supply enriched uranium because it was a commercial transaction. "Should there be any difficulty, we can still run the reactors using our MOX technology. Right now we are keeping it on a low key, though all engineering technologies have been established. We will continue to run them on low-enriched uranium."

Tarapur engineers were at their innovative best in developing technology and procuring spares which stopped coming from abroad after 1974. The tools and tackles and remote handling instruments for the core shroud of the reactor were developed by engineers from the Bhabha Atomic Research Centre (BARC), at Trombay, the Nuclear Fuel Complex, Hyderabad and the Atomic Fuels Division, BARC, Trombay.

The engineers faced a major challenge when the tubes in the secondary steam generators developed cracks. The generators were designed in such a way that the operators could not plug the leaks in the tubes without getting exposed to heavy doses of radiation. So the generators were isolated and the reactors derated from a capacity of 210 MW each to 160 MW each in 1985.

Chaturvedi said the main concern related to the reactor pressure vessel. During a recent inspection, NPC engineers found the pressure vessel and the shroud assembly in very good condition. "There were no cracks in them at TAPS unlike in reactors in Japan and the U.S. and some other Western countries."

Chaturvedi said that the NPC was upgrading the plant. "We are raising the level of safety as required internationally today. We have changed the pumps. We have additional pumps. We have changed all the piping. The new pipes are made of good material." He was confident that the reactors could be operated for another 25 to 30 years. Since the Tarapur reactors had already run for 30 years, "operating them for the next five years (alone) will be equivalent to 15 years of operation of a new reactor", he said.

According to Katiyar, more than 300 modifications have been made to the plant. The reactors had one start-up transformer and one battery bank earlier. Now there are two transformers and two battery banks. The number of ion exchangers for each unit has been increased from four to five. One more pump has been installed for cleaning up the reactor water. The piping made of stainless steel 304, which was susceptible to failure, has been replaced by piping made of a special material, SS 316 LN. The insulation for the piping has been upgraded. Since the turbine extraction line was susceptible to corrosion, the piping is now done using chromium molybdenum. The clean-up heat exchangers have been replaced.

Dr. Kakodkar said: "We are now looking at not just addition to nuclear power but addition at a continuous pace. The share of nuclear power in the overall electricity generation should go up. The fleet of the atomic energy programme will grow. TAPS, as the flagship, will continue to lead it."