im looking for some info about chernobyl

A city of west-central European U.S.S.R. north-northwest of Kiev. It was the site of a major nuclear power plant accident on April 16, 1986. Population (in 1986), 12,000.

切尔诺贝利：苏联欧洲部分中西部城市，位于基辅西北偏北。是1986年4月16日的一场核能大事故的所在地。人口（1986年）12,000

Chernobyl" Accident, accident at the Chernobyl" nuclear power plant in the Ukrainian republic of the Union of Soviet Socialist Republics (USSR) that produced a plume of radioactive debris that drifted over parts of the western USSR, Eastern Europe, and Scandinavia. The accident, which occurred on April 26, 1986, was the worst nuclear power accident in history. Large areas of the Ukrainian, Belorussian, and Russian republics of the USSR were contaminated, resulting in the evacuation and resettlement of roughly 200,000 people. The accident raised concerns about the safety of the Soviet nuclear power industry, slowing its expansion for a number of years, while forcing the Soviet government to become less secretive. The now independent countries of Ukraine and Belarus have been burdened with continuing and substantial costs for decontamination and health care because of the Chernobyl" accident.

THE ACCIDENT

The Chernobyl" nuclear power plant was one of the largest in the USSR. It was located just outside of the town of Pripyat", about 18 km (11 mi) northwest of the town of Chernobyl". The plant was only 16 km (10 mi) from the border between the Ukrainian and Belorussian republics and roughly 110 km (70 mi) north of Kyiv (Kiev), the capital and largest city of Ukraine. Construction of the plant began in the 1970s, with reactor No. 1 commissioned in 1977, followed by No. 2 (1978), No. 3 (1981), and No. 4 (1983). Each reactor had an electricity-generating capacity of 1,000 megawatts, and the four together produced about 10 percent of Ukraine"s electricity at the time of the accident. Two more reactors (No. 5 and No. 6, also capable of producing 1,000 megawatts each) were under construction at the time of the accident.

In the early morning hours of April 26, 1986, reactor No. 4 was operating at very low capacity (6 to 7 percent) during a planned shutdown. Plant personnel intended to monitor the performance of turbine generators, which supplied electric power for the plant"s own operation, during a changeover from standard to a backup source of power. The reactor"s design made it unstable at low power, and the operators were careless about safety precautions during the test. After a sudden power surge, two explosions destroyed the reactor core and blasted a large hole in the roof of the reactor building. Radioactive debris moved up through this hole to heights of 1 km (0.6 mi), carried by a strong updraft. Fires caused by the explosion and the heat of the reactor core fed the updraft.

An estimated 100 to 150 million curies of radiation (primarily radioactive isotopes of iodine and cesium) escaped into the atmosphere before cleanup crews were able to bring the fires under control and stabilize the situation some two weeks later. Initially, prevailing winds carried the radioactivity northwest from the plant across Belorussia and into Poland and Sweden, where heightened radiation levels detected on April 28 first brought the accident to the world"s attention. Subsequently, from May 1 to 5, wind patterns shifted so that the bulk of radioactivity was carried more directly north and northeast, over Belorussia and southwestern Russia.

After the explosion, firefighters and other workers arrived on the scene in an attempt to contain the blast. To reduce emissions, the team bombarded the reactor with 5,000 metric tons of shielding material consisting of lead, boron, sand, and clay. A second concrete foundation was constructed under the reactor to prevent contamination of groundwater. Finally, workers erected an enormous concrete-and-steel shell or “sarcophagus” over the damaged reactor to prevent radioactive materials, including gases and dust, from escaping. Initially, Soviet officials placed the death toll at 2 (both workers killed during the explosion at the No. 4 reactor) but by mid-August revised the figure to 31, reflecting deaths of workers from acute radiation exposure during the cleanup.

By mid-July, roughly three months after the accident, containment and cleanup had proceeded to the point where the plant"s management had moved back into the administration building just 300 m (about 1,000 ft) from the No. 4 reactor. In addition to reducing the radiation threat, a key objective to the cleanup effort was resumption of electric power generation at Chernobyl" before the onset of winter. The No. 1 and No. 2 reactors, in fact, were returned to service in November 1986 and the slightly damaged No. 3 unit was restarted in December 1987.