On 17 August 2009, a turbine in the hydroelectric power station of the Sayano-Shushenskaya Dam near Sayanogorsk in Russia failed catastrophically, killing 75 people and severely damaging the plant.

The Sayano-Shushenskaya Dam is located on the Yenisey River in south-central Siberia, Russia, about 30 kilometres (19 mi) south of Sayanogorsk, Khakassia.

[1] Turbines of the type used in this power plant have a very narrow working band at high efficiency regimes.

It was the first and only turbine in the station which was equipped with a new electro-hydraulic regulator of its rotational speed supplied by the Promavtomatika company.

[4] During the course of the repair, the turbine blades were welded, because after a long period of operation, cracks and cavities had once again appeared.

The vibrations exceeded the allowed specification in the beginning of July[3] and continued to increase with accelerated speed.

[3] On the night of 16–17 August, the level of vibration increased substantially,[5] and there were several attempts to stop the turbine.

As the plant general director, Nikolai Nevolko, was celebrating his anniversary, early in the morning he went to Abakan to greet the arriving guests, and none of the workers present wanted, or had the authority, to make decisions about further actions regarding the turbine.

The turbine often operated in the band II regime, which is accompanied by pulsation and strokes in the water flow.

[citation needed] On 4 October 2009, the official report about Sayano-Shushenskaya hydro accident was published by the Federal Environmental, Technological and Atomic Supervisory Service (Rostekhnadzor) on its website.

Names of people killed and those who bear responsibility for the accident, and other data including a historical and technical review about the plant and plans for its future, are given in the report.

[3] According to Rostekhnadzor, the automatic shutdown system of the water intake pipes' gates failed after failure of the turbine 2.

According to Bobrovski, it is common practice in the region to compensate for a peak load by overloading hydroelectric power plants.

He also stated that the energy system of the region is near collapse, as the main goal of its owners is to take out as much profit as possible, typically by cutting down on maintenance, investment, safety, and educational costs.

[13] He said that the former director of Sayano-Shushenskaya hydroelectric power station, Valentin Bryzgalov, had alerted that it is dangerous to operate the plant at its maximum loads when the turbines are starting to vibrate in the axial direction.

[16] On 11 September 2009, RusHydro disputed allegations that the dam overwhelmed the machinery hall leading to the destruction of turbine 2.

[17] On 21 August 2009, a website supporting rebel groups in Chechnya claimed that they were responsible for the blast, part of a new "economic war" which they were declaring on Russia.

A November 2010, peer-reviewed article in International Water Power and Dam Construction suggested a previously unpublicized direct cause for the turbine failures: draft tube waterhammer.

This frees the draft tube liquid to first surge towards the tailrace and then reverse, eventually slamming rapidly into the turbine with great force.

From the article: This hypothesis is that the explosion was caused by water column separation in the draft tubes of the destroyed units.

This, combined with compromised stud connections due to poor maintenance, can explain the extreme violence of this accident.A subsequent review for the 10th anniversary of the incident, published by the International Association for Hydro-Environment Engineering and Research (IAHR),[21] concluded that no intervening revelations had lessened the feasibility of this explanation.

[citation needed] Due to the accident, the town of Cheryomushki banned the sale of strong alcoholic beverages.

[31] Although smelters continue to work at their normal rate, RUSAL warned that in the longer term it may lose up to 500,000 tonnes (490,000 long tons; 550,000 short tons) of aluminum output due to the power shortage, and called for accelerating the construction of the Boguchany hydroelectric power station to replace the lost generating capacity.

On 19 August 2009, the 15 km (9.3 mi)-long spill had reached Ust-Abakan [ru], where it was cordoned off with floating barriers and chemical sorbents.

[9] Russian Prime Minister Vladimir Putin, awarded Juri Salnikov and Oleg Melnitchuck each with an Official Letter of Commendation.

Vapor clouds at the base of the spillway were expected to cause unwanted ice buildup on the construction site.

A team of climbers equipped with chainsaws and jackhammers was assembled to remove excess ice, and a heating system was installed under machine hall roof.

[citation needed] Russian Prime Minister Vladimir Putin personally switched turbine 6 to the load.

[56] It was reported that on 9 September 2009, Novy Fokus Mikhail Afanasyev, the editor of a regional news website, was attacked and beaten near his house in Abakan.

Earlier, he was charged for "spreading false information and defaming rescuers in his reports" by the local prosecutor's office.