Fatalities at the 6,400-MW Sayano Shushenskaya plant in southern Siberia rose to 71 on Tuesday after several bodies were recovered as water was drained from the turbine room that completely flooded following an explosion on Aug. 17 at the giant hydropower station in the Russian Federation. Four workers remain missing.
The plant’s owner, state-owned RusHydro, declared Aug. 25 a day of mourning for the victims of the disaster—which included staff of contractor organizations Gidroenergoremont, Technostroy, and OOPSK Avangard, as well as personnel at the hydropower plant. “Today, all the company’s personnel, from the North Caucasus to Kamchatka, are grieving for the insufferable loss and feel deep in their hearts the pain of our colleagues from the Sayano-Shushenskaya HPP,” RusHydro said in a statement.
The federal entity also recapped how the accident happened. It said that nine of the 10 turbines at the plant were in operation—hydroturbine 6 was in reserve—at the time of the accident on Aug. 17. The plant’s total active capacity was then 4,400 MW.
“At 4.15 Moscow Time, a tremendous bang was heard in the turbine room, followed by release of a column of water around hydro-turbine No. 2. Light and sound alarms came on at the Central Control Console. Loading was reduced to 0 MW with complete loss of the plant’s own needs and flooding of the turbine room building,” RusHydro said.
“At 5.20 Moscow Time, the emergency repair valves on the inflows to the hydro-turbines were closed down by hand from the crest of the dam and water access to the turbine room was cut off from the headrace. To replace the passage of the water through the turbines into the spillway dyke, at 7.32 Moscow Time, current was switched on from the mobile diesel generator on the gantry crane on the dam crest. The operation to lift the gates and release the water through free was completed at 7.50 Moscow Time. Throughout the period of the accident, there was no risk of water spilling over the top of the dam and the entire inflow into the [hydropower plant’s] dam was released free through the water release arches.
“As a result of external examination, it was discovered that hydro-turbines 2, 7 and 9 had been destroyed, turbines 1 and 3 seriously damaged and hydro-turbines 4 and 5 slightly damaged, that the metal structures of the roof of the turbine room has collapsed, that hydro-turbines 8 and 10 were damaged internally and that turbine 6 was in a satisfactory state. Transformers 1 and 2 had been destroyed, while transformers 3, 4 and 5 were in a satisfactory condition. It will be possible to determine the state of the turbines and transformers more precisely after the water has been pumped out of the turbine room and all the debris cleared. The outdoor switchgear-500 was not damaged and is working normally. No damage was caused to the body of the dam or the spillways.”
The plant in the Khakassia was a landmark project when it was completed in 1978. It straddles Siberia’s Yenisei River and features a 245-meter-high concrete dam that holds a water reservoir stretching over 621 square kilometers.
The actual cause for the accident has not been officially determined, although terrorism has been ruled out as an explanation. Officials continue to suggest that a technical breakdown was the cause for the explosion.
Sources: RusHydro, POWERnews