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Sayano-Shushenskaya power station accident

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 turbine hall was flooded, and a section of its roof collapsed. All but one of the ten turbines in the hall were destroyed or damaged. The entire power output of the plant, totalling 6,400 megawatts, was lost, leading to widespread power outages in the area. An official report on the accident was released in October 2009.

Background
The Sayano-Shushenskaya Dam is located on the Yenisey River in south-central Siberia, Russia, about south of Sayanogorsk, Khakassia. Before the accident, it was the largest hydroelectric power station in Russia and the sixth-largest in the world by average power generation. On 2 July 2009, RusHydro, the power station's operator, announced the station's all-time highest electricity output over 24 hours. Turbine 2 , comprising turbine and generator, of the Sayano-Shushenskaya power plant Turbines of the type used in this power plant have a very narrow working band at high efficiency regimes. If this band is exceeded the turbines begin to vibrate, caused by the pulsation of water flow and water strokes. These vibrations and shocks cause the turbines to degrade over time. Turbine 2 had experienced problems for a long time prior to the 2009 accident. 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 turbine runner was not properly rebalanced after these repairs, Turbine 2 was started on 16 August 2009 at 23:14 local time. At 23:44 it was running at a full load of 600 MW. During the night, its load varied between 10 and 610 MW. At the moment of the accident, which was 08:13 local time (00:13 GMT), its load was 475 MW and water consumption was . Vibration of the bearing was , which far exceeded the values of the other turbines by more than fourfold. The working life defined by the manufacturer for the turbines was specified as 30 years. At the moment of the accident, the age of the turbine was 29 years and 10 months. On 17 August 2009, the turbines were at a working level of . At this pressure the recommended power band for the turbines is 570–640 MW (band III) and the allowed band is 0–265 MW also (band I). Band 265–570 MW (band II) at this pressure is not recommended and output over 640 MW (band IV) is forbidden. On the day of the accident, turbine 2 worked as the plant's power output regulator and due to this, its output power changed constantly. The turbine often operated in the band II regime, which is accompanied by pulsation and strokes in the water flow. == Accident==
Accident
The accident occurred on 17 August 2009 at 08:13 local time (00:13 GMT). There was a loud bang from turbine 2. The turbine cover shot up and the rotor then shot out of its seat. (09.30 by official report The emergency diesel generator was started at 11:32. Nine out of the ten turbines were operating at the time, with a total output 4,400 MW. Turbine 6 was undergoing scheduled maintenance, but was ready for a restart. Oleg Myakishev, a survivor of the accident, described it as follows: ...I was standing upstairs when I heard some sort of growing noise, then I saw the corrugated turbine cover rise and stand on end. Then I saw the rotor rising from underneath it. It was spinning. I could not believe my eyes. It rose about three meters. Rocks and pieces of metal went flying; we started to dodge them... At that point the corrugated cover was nearly at roof level, and the roof itself had been destroyed... I made a mental calculation: the water is rising, 380 cubic meters per second, so I took to my heels and ran for the turbine 10. I thought that I wouldn't make it. I climbed higher, stopped, looked down, and saw everything getting destroyed, water coming in, people trying to swim... I thought: someone must urgently shut the gates to stop the water, manually... Manually, because there was no power, none of the protection systems had worked... ...Я стоял наверху, услышал какой-то нарастающий шум, потом увидел, как поднимается, дыбится рифлёное покрытие гидроагрегата. Потом видел, как из-под него поднимается ротор. Он вращался. Глаза в это не верили. Он поднялся метра на три. Полетели камни, куски арматуры, мы от них начали уворачиваться... Рифлёнка была где-то под крышей уже, да и саму крышу разнесло... Я прикинул: поднимается вода, 380 кубов в секунду, и — дёру, в сторону десятого агрегата. Я думал, не успею, поднялся выше, остановился, посмотрел вниз — смотрю, как рушится всё, вода прибывает, люди пытаются плыть... Подумал, что затворы надо закрывать срочно, вручную, чтобы остановить воду... Вручную, потому что напряжения-то нет, никакие защиты не сработали... --> On 9 September 2009 at 17:40 local time (09:40 GMT), a fire started in the turbine hall during repair works. Around 200 people were evacuated. There were no fatalities or injuries. ==Investigation==
Investigation
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. However, later the report and the press release on the report were removed from the 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. The report states that the accident was primarily caused by the turbine vibrations which led to the fatigue damage of the mountings of the turbine 2, including the cover of the turbine. It was also found that at the moment of accident at least six nuts were missing from the bolts securing the turbine cover. After the accident 49 recovered bolts were investigated, of which 41 had fatigue cracks. On 8 bolts, the fatigue damaged area exceeded 90% of the total cross-sectional area. This accusation was dismissed by Rakurs, the company which designed the automated safety system for the plant. Media speculation According to the newspaper Izvestia, the increased vibration of turbine 2 was going on for some 10 years and was well-known to the plant personnel. The former general director of the plant, Alexander Toloshinov, has said that the accident was most likely due to a "manufacturing defect" in a turbine. According to Toloshinov, the construction of the turbine blades of this type of turbine is not very reliable and cracks are known to develop in them under some working conditions. On 11 September 2009, RusHydro disputed allegations that the dam overwhelmed the machinery hall leading to the destruction of turbine 2. According to RusHydro, displacements of the dam are seasonal and have been reduced in recent years. The maximum displacement () was recorded in 2006, which was below the allowed maximum of . According to RusHydro, the scope of displacement between the anchor legs and the machinery hall does not exceed , which is less than the width between them (), and therefore the dam cannot overwhelm the machinery hall. 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. These claims were dismissed by authorities as "idiotic". 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. The immediate cause of this is proposed to be simply the too-sudden closure of the turbine wicket (flow-control) gates. Too-rapid closure results in rupture of the liquid column as the local pressure downstream of the gates goes to vapor pressure. This frees the draft tube liquid to first surge towards the tailrace and then reverse, eventually slamming rapidly into the turbine with great force. Only such a phenomenon seems capable of producing the extremely sudden, extremely large, and extremely vertical force which is evident from photographic and verbal descriptions of the damage. From the article: This hypothesis is that the explosion was caused by water column separation in the draft tubes of the destroyed units. This condition can readily be caused by a too-rapid wicket gate closure during unit load rejection. Adjustment of governor times to unsafe values to achieve fast response to operating load changes may have occurred in recent times in response to a need to improve grid frequency control. 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), concluded that no intervening revelations had lessened the feasibility of this explanation. ==Rescue operation==
Rescue operation
After the accident, the spillway was regulated to decrease the water level of the reservoir by per day. Flood water was pumped out from the engine room by 24 August 2009. On 28 August, the search and rescue operation was completed, and the state of emergency imposed in Khakassia on 17 August 2009, was lifted. == Aftermath ==
Aftermath
As a result of the accident, 75 people were killed. On 19 August 2009, a mourning day was announced in Khakassia. RusHydro declared 25 August a day of mourning at the company. A festival in the city of Abakan on 22 August was canceled. Due to the accident, the town of Cheryomushki banned the sale of strong alcoholic beverages. Damage In addition to turbine 2, turbines 7 and 9 also suffered severe damage and were destroyed, while the turbine room roof and ceilings fell on and caused additional damage to turbines 1 and 3, with slight damage to turbines 4, 5, 8, and 10. Turbine 6, which was in scheduled repair at the time of the accident, received only minor damage and was the only one of the station's 10 turbines that did not receive electrical damage due to shorting of the associated transformers. Water immediately flooded the engine and turbine rooms and caused a transformer explosion. Transformers 1 and 2 were destroyed, while transformers 3, 4, and 5 were left in satisfactory condition. Other damage was also severe as the machinery hall was destroyed, including the roof, ceilings, and floor. On 9 September 2009, RusHydro announced the damage caused by the incident: • Turbine 6: Flooded • Turbine 5: Flooding and electrical damage • Turbines 3 and 4: Moderate electrical and mechanical damage. Some damage to the concrete structures around them. • Turbines 1, 8, and 10: Severe electrical and mechanical damage. Some damage to the concrete structures around them. • Turbines 7 and 9: Completely destroyed, with extreme damage to the concrete structures around them. • Turbine 2: Destroyed completely, including the concrete structures around it. Although smelters continue to work at their normal rate, RUSAL warned that in the longer term it may lose up to 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. Environmental impact The accident caused an oil spill, releasing at least of transformer oil which spread over downstream of Yenisei. The oil, which spilled during the approximately 2–3 hour cutoff of river flow when all the gates of the dam were closed, killed of cultivated trout in two riverside fisheries, with its impact on wildlife as yet unassessed. On 19 August 2009, the -long spill had reached , where it was cordoned off with floating barriers and chemical sorbents. The oil spill was fully removed by 25 August 2009. Financial impact Share prices Trading in RusHydro shares at the Moscow Interbank Currency Exchange was suspended for two days. On the London Stock Exchange, the share price dropped more than 15%. The power plant was insured for US$200 million by Russian insurance company ROSNO, part of Allianz group, and re-insured by Munich Re. Compensation The Russian government decided to pay compensation of 1 million rubles (US$31,600) to each victim's family, and 100,000 rubles (about US$3,100) to each survivor, while RusHydro decided to pay a further 1 million rubles in compensation. RusHydro also decided to buy housing for 13 families of killed workers with underage children. There are also programs to support these children in kindergartens and schools and to provide higher education. In addition, a special program is planned for the reconstruction and development of the Cheryomushki settlement, the main settlement where the power plant workers live. Personnel The director of the plant, Nikolai Nevolko, was replaced by Valerii Kjari. Several people were awarded for their heroic actions during the accident. Russian Prime Minister Vladimir Putin, awarded Juri Salnikov and Oleg Melnitchuck each with an Official Letter of Commendation. == Repairs ==
Repairs
At the time, repairs were estimated to take up to four years. Over 2,000 people were involved in the rescue work and liquidation of the consequences after the disaster. According to Russian Energy Minister Sergei Shmatko, the rebuilding of the engine room alone was estimated to cost 40 billion rubles (€880 million, US$1.3 billion). RusHydro also negotiated a loan with the European Bank for Reconstruction and Development. According to RusHydro, turbines 4, 5, and 6 would probably be repaired. Turbines 7 and 9 were too damaged and were disassembled. The machinery hall, heating system, electricity supply, and sewage tunnels were under repair. The machinery hall and its heating system also underwent repairs. The repair work was performed continuously, 24 hours a day. During repairs, water was being discharged using the spillway only. Special measures were taken to ensure its safe operation in winter conditions. Water gates were modified to be temporarily locked into an intermediate position for better flow control. 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 the machine hall's roof. By 27 December 2009, there were on-going or prepared dismantling of turbines 1, 2, 3, 4, 7, 8, 9, and 10. Only turbines 5 and 6 were to be repaired in situ. The other turbines were to be replaced, repaired in the factory and/or modernized. Turbine 6 was restarted on 24 February 2010. Russian Prime Minister Vladimir Putin personally switched turbine 6 to the load. Turbine 5 was brought under load on 22 March. On 14 April 2010, the process of dismantling turbine 2 and the infrastructure surrounding it was finished.. On 30 June the same year, turbine 4 was started without a load to dry its electrical coils, to test it and to prepare it for switching under load later in 2010. It was fully restarted on 4 August 2010. By July 2010 the replacement of turbine 3 was underway and expected to be completed in December 2010. The new turbine has better electrical and hydrodynamic characteristics and a 40-year working life. On 6 July 2011, a ship loaded with new parts for the turbines left Saint Petersburg. On 8 July 2011, turbines 3, 4 and 5 were working under full load and turbine 6 was in reserve. On 11 November 2014 the renovations and repairs were fully completed. ==Attack on journalist==
Attack on journalist
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. Afanasyev believes that the attack is "probably connected to his articles about the accident". ==See also==
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