The Nurek hydroelectric station is included in the list of the largest hydroelectric power plants in the world and is the flagship of the energy industry of Tajikistan. The station is located in the Pulisanga gorge, near the city of Nurek in the Khatlon region of the republic, in the lower reaches of the Vakhsh river. The Nurek hydroelectric station is part of the Vakhsh cascade, which consists of six existing and three hydropower plants under construction.
History of construction and technical aspects
The construction of the Nurek hydroelectric station lasted more than ten years. In the mid-1950s, Kharkov Plant named after Kirov. The preparation of all design documentation was completed in 1961.
In the same year, the construction of the station began in the Tajik SSR. The excavator bucket, which removed the first cubic meters of soil, still rests on a pedestal in the station, recalling the difficult everyday life of the first builders.
Commissioning of the station and the launch of the first hydraulic unit took place in 1972, the launch of the last, ninth unit, in 1979. Each of the nine units with radial-axis turbines of the Nurek hydroelectric station had a capacity of 300 mW, in 1988 it was increased to 333 mW, after which the total capacity of the station exceeded 3 gW. Today, the Nurek hydroelectric power station accounts for about 80% of all electricity generated in the republic.
The Nurek hydroelectric power station has a lot of underground structures, which is quite typical for stations with high stone-filled dams. The phased launch of the power plant equipment required the construction of three tiers of temporary construction tunnels.
Water for the operation of turbines of hydraulic units is supplied through three concrete pressure tunnels with a length of more than 400 and a diameter of 10 meters, ending in collectors. From each stream is distributed into three water conduits with a length of more than 600 and a diameter of 6 meters, which supply water directly to the turbine blades.
Dam and reservoir
The dam of the Nurek hydroelectric power station has a height of 300 meters, which until 2013 made it the highest in the world. 56 million cubic meters of soil was required for the construction of this stone-filled dam with concrete plug. Her body consists of 11 structural elements.
The reservoir formed by the dam has a normal retaining level of 910 meters, a width of 1 kilometer and a length of about 70 kilometers. The average depth of the artificial reservoir - 107 meters, volume - 10.5 cubic meters. kilometers, mirror area - 98 square meters. kilometers. Excess water is discharged through a five-kilometer tunnel punched into the rock. The size of the reservoir made it possible to organize shipping on it.
The filling of the Nurek reservoir began in 1972. As in the days of the Tajik SSR, and today the reservoir has a great influence on the agriculture of the region. Its waters are used for irrigation purposes and irrigate more than 1 million hectares of land that has become fertile.
Accidents at the Nurek power plant
The accident, similar to the incident at the Sayano-Shushenskaya hydroelectric station, occurred on July 9, 1983. At 22 hours 42 minutes there was a blow in the area of the 1st hydraulic unit, and station workers noticed a stream of water beating from the turbine shaft. The equipment was immediately stopped and the flow blocked by an emergency shutter.
Inspection showed that two-thirds of the turbine cover mounting studs were torn out, and the turbine itself was close to a breakdown and the beginning of the rise, which would entail great damage and human casualties. Thanks to the clear actions of the staff, everything was done only by flooding the lower premises of the station.
The investigation found that the cause of the destruction was the fatigue of the metal, which appeared as a result of insufficient tightening of the studs. From that moment on, Tajikistan's hydroelectric power plants introduced mandatory ultrasonic flaw detection of turbine cover fastening studs twice a year. Such control measures made such accidents impossible in the future.
In 1999, due to wear and tear of the equipment, two switchgears with voltage of 220 and 500 kilovolts failed.
On April 17, 2006, during the repair of the drainage channel of the reservoir, inadvertently, stopping gates were opened and water rushed into the channel of the channel. Violation of the rules for safe work was the cause of the death of three workers.
Reconstruction
On August 12, 2016 in Dushanbe, a conference was held with the participation of the government of the republic, at which a decision was made to reconstruct the Nurek hydroelectric station. The modernization of the station will be carried out in two stages, the cost of work is estimated at $ 700 million.
Until 2000, two switchgears and two turbine impellers were replaced. The current reconstruction provides for the replacement of all nine hydraulic units of the station, six autotransformers and the strengthening of dams and spillways.
As a result of the comprehensive modernization of the Nurek hydroelectric station, the design capacity of the station will increase to 3.2 gW, and the updated equipment will ensure long-term uninterrupted power generation.