The Tarapur Atomic Power Station (TAPS) located near Boisar, Maharashtra, is the oldest nuclear power plant in India.
The power station comprises two 120MW boiling water reactor (BWR) units commissioned in October 1969 and two pressurised heavy water reactor (PHWR) units commissioned between 2005 and 2006.
Owned and operated by the state-run Nuclear Power Corporation of India (NCPIL), the Tarapur nuclear power station completed 50 years of operation in October 2019.
The first two units of the plant have been thoroughly refurbished following a comprehensive safety assessment carried out by the India’s Atomic Energy Regulatory Board (AERB), after the completion of 30 years of operation.
The power station produced more than 193 billion units of electricity as of September 2019, with the two old units accounting for more than 98 billion units.
Tarapur atomic power station background
Construction of the Tarapur nuclear power station was started in October 1964, following the signing of a contract between the governments of India and US in May 1964 to collaborate for building India’s first ever nuclear power plant along the west coast of India.
The construction phase involved 120 Americans, while GE supplied both the BWR units of the plant.
Although the US had agreed to supply enriched uranium for the Tarapur atomic power station for 30 years, the fuel supply was cut down after India’s nuclear bomb test at Pokhran, in 1974.
The power station later started using imported uranium fuel supplied by other countries including China, France, and Russia, in compliance with the International Atomic Energy Agency (IAEA) safeguards.
Safety upgrades for Tarapur units one and two
Although the initial rated power of both TAPS 1 and 2 was 210MW, it was reduced to 160MW after the secondary steam generators were isolated in 1984 due to frequently reported tube leakages.
Further, a number of modifications were carried out between 2005 and 2006 based on the AERB’s comprehensive safety assessment for the continued long-term operation of TAPS units one and two.
The emergency power supply system for the units was upgraded by replacing the three pre-existing 350kW diesel generators (DGs) with three new 800kW DGs.
The pre-existing shared shutdown cooling system was also upgraded to operate independently for each unit with the installation of additional pump and heat exchangers. The fuel pool cooling system was made independent of shutdown cooling system.
The supplementary control room (SCR) for units one and two was also retrofitted as part of the safety upgrade initiative.
TAPS units three and four details
Designed and developed by NPCIL, the third and fourth reactor units at Tarapur atomic power station are the first PHWR units to be used in India. Each horizontal pressure tube reactor unit, with physically separated independent safety and shutdown systems, has a design net capacity of 540MW.
Construction of the TAPS units three and four was started in May and March 2000, respectively. The unit four was connected to the grid in June 2005, while the unit three was commissioned in August 2006.
GE was the turnkey engineering, procurement, and construction (EPC) contractor for the TAPS units one and two.
Larsen & Toubro (L&T) was engaged for the main plant civil works, service water system, primary steam piping, composite chilled water, and heating, ventilation and air-conditioning (HVAC) packages, as well as electrical and instrumentation works for the Tarapur units three and four.
Other construction contractors involved in the last two units of the plant were Gammon India, Afcons Infrastructure, and Metcon.
Bharat Heavy Electricals (BHEL) designed the steam generators for all four reactor units of the Tarapur nuclear power station.
TVEL Fuel Company, a subsidiary of Russia’s state-run Rosatom, was contracted by the Department of Atomic Energy, Government of India, to supply uranium fuel pellets for the BWR reactor units of the Tarapur nuclear power plant in January 2019.