The utility and the Emergency Situations Ministry said that the accident on 17 August was due to some kind of hydraulic failure or rupture, but the cause has not yet been established.
The plant has 10 generating units and RusHydro said the focus of the accident was around unit No 2. Heavy damage was also suffered by units No 7 and No 9. The three units are so badly damaged as to be beyond repair.
Parts of the building collapsed, resulting in damage also to units No 3, No 4 and No 5. About 1,200m2 of the roof collapsed.
A compensation fund has been established for victims of the accident.
RusHydro has despatched 400 technical workers to the damaged plant while the search continues and dewatering of the flooded surface powerhouse, built at the foot of the concrete gravity arch dam, gets underway. The workers are its own staff and from contractors and equipment providers and consultants.
Draining the wrecked building is expected to take about two days to expose the remaining collapsed structures, equipment and rubble. The water is being removed at approximately 4,200m3/hour.
With high inflows to the reservoir, as has been the case for a number of months, water continues to be discharged at approximately 1700m3/sec through the partially open gates. The rate is about a fifth less than that required immediately following the accident.
Downstream of the dam the authorities have used 50 tonnes of chemical reagents to treat oil pollution in the river due to the accident at the plant. The river levels have been fluctuating with the spilling of inflow from the reservoir.
The utility said that when repairs are undertaken it expects unit No 6 to be the first to resume operation. The unit has been out of service for refurbishment for most of the year and the work was due to finish this month.
However, there are no indications of how long the facility will take to be repaired or the time needed for the accident investigation.
Sayano-Shushenskaya is built on the Yenisei river and was completed in the late 1980s. The first generating unit was commissioned in 1978.
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