Chernobyl Nuclear Power Plant

The Chernobyl Nuclear Power Plant or Chernobyl Nuclear Power Station (Ukrainian: Чорнобильська атомна електростанція, Russian: Чернобыльская АЭС) is a nuclear power station under decommissioning near the city of Pripyat, Ukraine, 14.5 km (9.0 mi) northwest of the city of Chornobyl, 16 km (9.9 mi) from the Belarus–Ukraine border, and about 110 km (68 mi) north of Kiev. Reactor No. 4 was the site of the Chernobyl disaster in 1986 and the power plant is now within a large restricted area known as the Chernobyl Exclusion Zone. Both the zone and the former power plant are administered by the State Agency in Administration of Exclusion Zone (Ministry of Ecology and Natural Resources).

The nuclear power plant site clean-up is scheduled for completion in 2065. On January 3, 2010, a Ukrainian law stipulating a programme toward this objective came into effect.

Construction

The V.I. Lenin Nuclear Power Station (Russian: Чернобыльская АЭС им. В.И.Ленина) as it was known during the Soviet times, consisted of four reactors of type RBMK-1000, each capable of producing 1,000 megawatts (MW) of electric power (3.2 GW of thermal power), and the four together produced about 10% of Ukraine's electricity at the time of the accident.

The Chernobyl station is 18 km (11 mi) northwest of the city of Chernobyl, 16 km (9.9 mi) from the border of Ukraine and Belarus and about 100 km (62 mi) north of Kiev. Construction of the plant and the nearby city of Pripyat, Ukraine to house workers and their families began in 1970, with Reactor No. 1 commissioned in 1977. It was the third nuclear power station in the Soviet Union of the RBMK-type (after Leningrad and Kursk), and the first nuclear power plant on Ukrainian soil.

The completion of the first reactor in 1977 was followed by reactor No. 2 (1978), No. 3 (1981), and No. 4 (1983). Two more blocks, numbered 5 and 6, of more or less the same reactor design, were planned at a site roughly a kilometer's distance from the contiguous buildings of the four older blocks. Reactor No. 5 was around 70 % complete at the time of block 4's accident and was scheduled to come online approximately six months later, on 7 November 1986. In the aftermath of the accident, the construction on No.5 and No. 6 was suspended, and eventually cancelled in April 1989, just days before the third anniversary of the 1986 explosion. Reactor Nos. 3 and 4 were second generation units, whereas Nos. 1 and 2 were first-generation units (like those in operation at Kursk Nuclear Power Plant). Second-generation RBMK designs were fitted with a more secure containment structure visible in photos of the facility.

Electrical systems

The power plant is connected to the 330 kV and 750 kV electrical grid. The block has two electrical generators connected to the 750 kV grid by a single generator transformer. The generators are connected to their common transformer by two switches in series. Between them, the unit transformers are connected to supply power to the power plant's own systems; each generator can therefore be connected to the unit transformer to power the plant, or to the unit transformer and the generator transformer to also feed power to the grid.

The 330 kV line is normally not used, and serves as an external power supply, connected to a station's transformer - meaning to the power plant's electrical systems. The plant is powered by its own generators, or at an event gets power from the 750 kV national grid through the main grid backup feed in transformer, or from the 330 kV level feed in grid transformer 2, or from the other power plant blocks via two reserve busbars. In case of total external power loss, the essential systems can be powered by diesel generators. Each unit's transformer is therefore connected to two 6 kV main powerline switchboards, A and B (e.g. 7A, 7B, 8A, 8B for generators 7 and 8), powering principal essential systems and connected to even another transformers at voltage 4 kV which is backed up twice (4 kV reserve busbar).

The 7A, 7B, and 8B boards are also connected to the three essential power lines (for the coolant pumps), each also having its own diesel generator. In case of a coolant circuit failure with simultaneous loss of external power, the essential power can be supplied by the spinning down turbogenerators for about 45–50 seconds, during which time the diesel generators should start up. The generators are started automatically within 15 seconds at loss of off-site power.

Turbo generators

The electrical energy is generated by a pair of 500 MW hydrogen-cooled turbo generators. These are located in the 600 m (1,969 ft)-long machine hall, adjacent to the reactor building. The turbines—the venerable five-cylinder K-500-65/3000—are supplied by the Kharkiv turbine plant; the electrical generators are the TBB-500. The turbine and the generator rotors are mounted on the same shaft; the combined weight of the rotors is almost 200 t (220 short tons) and their speed is 3000 rpm.

The turbo generator is 39 m (128 ft) long and its total weight is 1,200 t (1,300 short tons). The coolant flow for each turbine is 82,880 t/h. The generator produces 20 kV 50 Hz AC power. The generator's stator is cooled by water while its rotor is cooled by hydrogen. The hydrogen for the generators is manufactured on-site by electrolysis. The design and reliability of the turbines earned them the State Prize of Ukraine for 1979.

The Kharkiv turbine plant (now Turboatom) later developed a new version of the turbine, K-500-65/3000-2, in an attempt to reduce use of valuable metal. The Chernobyl plant was equipped with both types of turbines; Block 4 had the newer ones. The newer turbines, however, turned out to be more sensitive to their operating parameters, and their bearings had frequent problems with vibrations.

Reactor fleet

Four RBMK reactors were at Chernobyl Nuclear Power Plant, No. 1-4. The construction of two partially completed reactors, No. 5 and 6, was suspended immediately after the accident at reactor No. 4, and was eventually cancelled in 1989. Reactors No. 1-3 continued to operate after the accident. Reactor No. 2 was permanently shut down in 1991 after a fire broke out due to a faulty switch in a turbine.

Reactors No. 1 and 3 were eventually closed due to an agreement Ukraine made with the EU in 1995. Ukraine agreed to close the remaining units in exchange for EU assistance in modernizing the shelter over reactor No. 4 and improving the energy sector of the country, including the completion of two new nuclear reactors, Khmelnitski 2 and Rovno 4. Reactor No. 1 was shut down in 1996 with No. 3 following in 2000.

Accidents

1982: Reactor No. 1 partial meltdown

On September 9, 1982, a partial core meltdown occurred in Reactor No. 1 at the Chernobyl plant. The extent of the damage was minor, but the accident was not made public until several years later. The reactor was repaired and put back into operation within a few months.

1986: Reactor No. 4 disaster

On Saturday, April 26, 1986, a disaster occurred at Reactor No. 4, caused by a catastrophic power increase resulting in core explosions and open-air fires. This caused large quantities of radioactive materials and airborne isotopes to disperse in the atmosphere and surrounding land. The disaster has been widely regarded as the worst accident in the history of nuclear power in the world. As a result, Reactor No. 4 was completely destroyed and is being enclosed in a concrete and lead sarcophagus to prevent further escape of radioactivity. Large areas of Europe were affected by the accident. The radioactive cloud spread as far away as Norway.

1991: Reactor No. 2 fire

The Chernobyl Nuclear Plant utilized one large, open turbine hall for all four reactors without any separating walls. Each reactor had two turbines. On October 11, 1991, a fire broke out in the turbine hall of Reactor No. 2. The fire began in Reactor No. 2's Turbine 4 (ТГ-4 in Russian) while the turbine was being idled for repairs. A faulty switch caused a surge of current to the turbine, igniting insulating material on some electrical wiring. This subsequently led to hydrogen, used as a turbine coolant, being leaked into the turbine hall "which apparently created the conditions for fire to start in the roof and for one of the trusses supporting the roof to collapse." The adjacent reactor hall and reactor were unaffected.

2013 collapse

On February 13, 2013, a 600-square-metre (6,500-square-foot) portion of the roof and wall adjacent to the covered part of the turbine hall collapsed into the entombed area of the turbine hall. The collapse did not affect any other part of the Object Shelter or the New Safe Confinement. No variances in radiation levels as a result of the incident were detected. The roof which collapsed was built after the Chernobyl disaster. It was later repaired.

Plant shutdown and decommissioning

After the explosion at Reactor No. 4, the remaining three reactors at the power plant continued to operate. The schedule for plant decommissioning is intimately wrapped with the dismantling of Reactor No. 4 and the decontamination of its environs. The Chernobyl New Safe Confinement will have equipment which will make decommissioning relatively incidental to, yet an integral part of, the cleanup of the exploded reactor. The majority of the external gamma radiation emissions at the site are from the isotope caesium-137, which has a half-life of 30.17 years. As of 2016, the radiation exposure from that radionuclide has declined by half since the 1986 accident.

Reactor No. 1

In November 1996, following pressure from international governments, Reactor No. 1 was shut down. Removal of uncontaminated equipment has begun at Reactor No. 1 and this work could be complete by 2020–2022.

Reactor No. 2

In October 1991, Reactor No. 2 caught fire, and was subsequently shut down. Ukraine's 1991 independence from the Soviet Union generated further discussion on the Chernobyl topic, because the Rada, Ukraine's new parliament, was composed largely of young reformers. Discussions about the future of nuclear energy in Ukraine ultimately moved the government toward decision to cancel the operation of Reactor No. 2. In the mid 1990s, there were plans to restart reactor No. 2. but ultimately they were never carried out and the reactor remained shut down.

Reactor No. 3

In December 2000, Reactor No. 3 was shut down, and the plant as a whole ceased producing electricity. On April 9, 2015, units 1–3 entered the decommissioning phase.

Reactor No. 4 sarcophagus replacement

Originally announced in June 2003, a new steel containment structure named the New Safe Confinement would be built to replace the aging and hastily built sarcophagus that protected Reactor No. 4. Though the project's development has been delayed several times, construction officially began in September 2010. The New Safe Confinement was financed by an international fund managed by the European Bank for Reconstruction and Development (EBRD) was designed and built by the French-led consortium Novarka. Novarka is building a giant arch-shaped structure out of steel, 270 m (886 ft) wide, 100 m (328 ft) high and 150 m (492 ft) long to cover the old crumbling concrete dome that is currently in use.

This steel casing project is expected to cost $1.4 billion (£700 million, €1 billion), and is expected to be completed by 2017. The casing will also meet the definition of a nuclear entombment device. A separate deal has been made with the American firm Holtec to build a storage facility within the exclusion zone for nuclear waste produced by Chernobyl.

On 14 November 2016, the arch began its expected five-day placement over the existing sarcophagus; however, it ended up taking fifteen days to complete on 29 November 2016.

General directors

• 1970–1986 Viktor Bryukhanov
• 1986–1987 Erik Pozdyshev
• 1987–1992 Mykhailo Umanets
• 1994–1998 Serhiy Parashyn
• 2004–2005 Oleksandr Smyshliayev
• 2005–present Igor Gramotkin