The announcement follows rumors circulated in the Ukrainian media over the past few days of rising radiation levels in the area. Energoatom released a statement on June 3 saying the country's four nuclear plants were running smoothly.
However, Viktor Stovbun, Energoatom's executive director, told the national TV channel Inter on Thursday evening that the security system at the Rovno plant "gave an alert on a rupture in a pipe supplying water to the reactor. This occurred in the secondary circuit, which does not come into contact with radioactive materials."
The Rovno power plant consists of four VVER pressurized water reactors. Each has a primary cooling circuit, which takes heat from the reactor core, and a separate secondary circuit, in which water is boiled using heat from the primary, providing steam to drive a turbine linked to a power generator.
Ukraine remains heavily reliant on nuclear power, despite having experienced the world's worst nuclear disaster, the 1986 Chernobyl reactor explosion. Nuclear power accounts for almost half of national electricity generation.
Stovbun said the recent accident was even less significant than Wednesday's leak from the water cooling system of Slovenia's only nuclear power plant. The accident sparked alarm in other EU states, but the Slovenian Nuclear Safety Administration said no radiation was released.
The Ukrainian official said: "Whereas up to three cubic meters were leaked [in Slovenia], our leak was a mere three liters per hour."
Ukraine has four operational nuclear plants with a total capacity of around 14 GW. In 2006, the government approved a nuclear power strategy under which 11 new reactors are to be built by 2030, to more than double nuclear generating capacity.
The country is also seeking to develop uranium enrichment to ease its energy dependence on neighboring Russia, which supplies all Ukraine's nuclear fuel.