MOSCOW, Oct. 12— Officials said today that no radioactivity escaped during a fire that occurred on Friday night at the Chernobyl nuclear power plant, site of the infamous nuclear eruption five years ago.
About 300 firefighters and 60 fire trucks were rushed to fight the blaze from as far away as Zhitomir, 100 miles away, and Kiev, 60 miles away, and brought it under control by 11:30 P.M., three and a half hours after it began, officials said.
The fire destroyed the roof over a generator attached to the No. 2 reactor, one of three still functioning since the April 1986 disaster destroyed the No. 4 reactor.
The blaze was evidently limited to the area of the turbines, which are in a building adjoining a separate building housing the reactors, and did not affect the nuclear reactors. Officials said workers immediately shut the No. 2 reactor down, but that the first and the third continued to operate. Each reactor feeds two turbines.
Officials later said only one of the turbines of the third reactor was still operating, because the second one, located near the second reactor, was idled.
Spokesmen for the Soviet Ministry of Nuclear Power Industry and for the Soviet Hydrometeorology Committee, which monitors radiation, said no radioactivity was released during the fire, and radiation levels were unchanged at the plant and in surrouding regions. Fire Laid to Faulty Switch
According to a statement issued by the spokesman of the Ministry of Nuclear Power Industry, Yevgeny Ignatenko, the fire broke out shortly after 8 P.M. when a faulty switch suddenly sent current to a turbine and generator, starting fires in the wiring.
The spokesman said workers shut down the No. 2 reactor within a minute, drained oil from the turbine and replaced flammable hydrogen in the generator with nonburning nitrogen. The hydrogen is apparently used to cool the generator.
But the fire in the bus ducts, which carry the high-tension wires, led to the escape of hydrogen 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," an official said A Month for Repairs
The press agency Tass reported that according to Nikolai Skreka, the deputy director of the plant, it would take about a month to repair the damage from the fire.
Mr. Ignatenko said that the automatic systems and firefighters worked succesfully, and that the fire was fully put out by 11:30 P.M. He said a commission had started work today to investigate the fire.
Tass reported that Vladimr Yavorivsky, head of the Ukrainian parliamentary commission charged with overseeing the consequences of the 1986 Chernobyl disaster, demanded that the entire power station be immediately shut down. The same demand was made by French Green environmentalists in the European Parliament now meeting in Strasbourg.
In contrast to the 1986 eruption, when the Soviet Government was slow and evasive in reporting on the disaster, the Soviet media this time gave quick and detailed reports.
Map of the Soviet Union indicating Chernoybl.
