The Cabinet approved the draft agreement at a meeting chaired by Prime Minister Sheikh Hasina on Monday.
After the meeting, Cabinet Secretary Mohammad Shafiul Alam told reporters that Russia would offer $11.38 billion of the estimated project cost of $12.65 billion.
The repayment period will be 30 years with a 10-year grace period.
Bangladesh will have to start yearly repayments in March 2027, the cabinet secretary said.
The annual interest rate will be below 4 percent.
Shafiul said the agreement might be signed in July or August this year in Dhaka or Moscow.
The government expects the first unit of the plant, having a 50-year lifespan, to be commissioned in 2021.
Prime Minister Sheikh Hasina laid the plant’s foundation stone in October 2013.
Parliament passed a bill in August 2014 to form the Nuclear Power Plant Company Bangladesh, a unit under the Bangladesh Atomic Energy Commission, to run the plant.