Explanation:

Tarapur Atomic Power Station was constructed initially with two boiling water reactor (BWR) units under the 1963 123 Agreement between India, the United States, and the International Atomic Energy Agency (IAEA). It was built for the Department of Atomic Energy by GE and Bechtel. Units 1 and 2 were brought online for commercial operation on 28 October 1969 with an initial power of 210 MW of electricity. Later on this was reduced to 160 MW due to technical difficulties. These were the first of their kind in Asia. More recently, an additional two pressurised heavy water reactor (PHWR) units of 540 MW each were constructed by BHEL, L&T and Gammon India, seven months ahead of schedule and well within the original cost estimates. Unit 3 was brought online for commercial operation on 18 August 2006, and unit 4 on 12 September 2005.