The reactor pressure vessel and four steam generators were manufactured at the Atommash plant in southern Russia and were shipped in April.
The RPV, a 320-tonne component which will contain the nuclear reactor coolant, core shroud, and the reactor core and fuel, took about two years to manufacture.
Russia is building two VVER-1,200 pressurised water reactor units at the Rooppur site, about 150 km from the capital Dhaka, under a general contract signed in 2015.
First concrete for Rooppur-1 was poured in November 2017 and for Rooppur-2 in July 2018.