As many as 61% of voters in Sunday's referendum voted in favour of the construction of a second nuclear power plant (NPP) in Bulgaria, preliminary data of the Central Election Commission (CEC) showed.
However, turnout was below the voting threshold.
A total of 37.93% of people who went to the polling stations answered negatively, according to preliminary CEC data based on all ballots counted.
The referendum question was worded as follows: "Should we develop nuclear energy in the Republic of Bulgaria by building a new nuclear plant?"
CEC did not provide final voter turnout data. According to data as of 1500 GMT on Sunday, it stood at 17.42%. Polling stations closed at 1800 GMT.
According to local agency Alpha Research data based on a parallel count of the voting protocols, some 1.6 million people, or 21.8% of eligible voters, went to the polling stations.
The outcome of the referendum will be recognised as valid if at least 4.3 million people vote, as many as in the latest parliamentary elections. If turnout is above 20% with at least half of the voters saying 'yes' the issue will be included in parliament's agenda.
The referendum was initiated by the opposition Socialist party after in 2012 Bulgaria's centre-right government abandoned plans to build a 2,000 megawatt (MW) plant, for which it had hired Russia's Atomstroyexport, due to disagreement over its estimated cost and failure to attract a strategic investor. According to the government in Sofia, the project would cost at least 10.35 billion euro ($13.9 billion), while the Russian side estimated it at some 6.3 billion euro.
Bulgaria has one NPP, in the Danubian town of Kozloduy, which remained with two operational reactors of 1,000 megwatts (MW) each after the country closed down four units of 440 MW each to address nuclear safety concerns of the European Union prior to its accession to the bloc. Bulgaria joined the EU in 2007. In April 2012 the government decided to add another 1,000 MW reactor to the Koloduy plant.