Energoatom said that the radiation levels at the Zaporizhia nuclear power plant remain normal and unchanged.
The affected unit has been shut down, the company said adding that the accident classified as Level Zero of the International Nuclear and Radiological Event Scale (INES).
A commision to investigate the accident has been set up at the nuclear plant, Energoatom said.
Nuclear power occupies one of the most prominent places in the Ukrainian economy. Over recent years, having only 22.8% of the installed capacity, nuclear power plants during autumn and winter maximum loads generated about 53% of the country's electricity. Currently there are 15 operating power units at four Ukrainian NPPs. Ukraine imports about $600 million worth of nuclear fuel from Russia on the average annually, which is comparable with the indicators reported in first half of 2014 (279 million tons).
The Zaporizhia nuclear plant with an installed generating capacity of 6,000 megawatt is the biggest energy facility in Ukraine and Europe. It generates about 50% of electricity produced by Ukraine’s nuclear plants and accounts for more than 22% of the aggregate electricity generation in the country.
In April 1986, Ukraine witnessed the world's worst nuclear disaster when an explosion at the Chernobyl nuclear power plant released radiation, which spread over the western part of the Soviet Union and Europe.