Sberbank's chief, German Gref, told Russian Prime Minister Vladimir Putin the loan would be granted at low rates, with the first 10 billion-ruble credit line to be opened before the end of the year, the government said in a statement on Tuesday.
A surge of water destroyed a turbine room at the Sayano-Shushenskaya hydroelectric dam in eastern Siberia on August 17. RusHydro said on Tuesday 71 workers had been killed and four more were still missing.
RusHydro has said it will take three years to repair the dam and analysts have estimated repair costs at around 40 billion rubles.
The chief executive of aluminum producer RUSAL, one of the station's main customers, said last week repairs on the dam could take between four and five years.
RusHydro shares were down 1.7 percent down at 0836 GMT, slightly underperforming the broader MICEX index.
(Writing by Dmitry Zhdannikov; editing by John Stonestreet)