Four top Polish state-controlled firms have inked a letter of intent to build the country's first three gigawatt nuclear energy plant, a joint press release said Thursday.

Power utilities PGE, Tauron and Enea as well as global copper giant KGHM Polska Miedz will take shares in a special vehicle, PGE Energia Jadrowa SA (PGE Nuclear Energy), set up to develop Poland's nuclear power sector from scratch.

Global ratings agency Fitch on Thursday was optimistic about the project, which is estimated to cost between 9-12 billion euros (11.3-15.1 billion dollars).

"A possible joint venture between four Polish state-controlled companies will share the risks and speed up the progress of the country's first nuclear power plant," a Fitch Ratings statement said.

Keen to diversify its electricity sector away from coal, Poland has decided to push on with nuclear power despite Japan's Fukushima nuclear disaster and the decision by neighbouring Germany to phase out atomic energy.

An ex-communist country of 38.2 million, Poland relies on coal for about 90 percent of its electricity -- far exceeding the EU average of around 30 percent.

According to PGE Energia Jadrowa chief Aleksander Grad, operations could begin in 2023.

PGE is Poland's largest power provider and one of the largest companies of its kind Central and Eastern Europe.

Three global nuclear power giants have expressed interest in building the facility, including the French EDF/Areva and the US-Japanese firms Westinghouse Electric Company LLC as well as GE Hitachi Nuclear Energy.

In an earlier bid to diversify Poland's energy mix, the same four Polish firms joined Polish oil and gas giant PGNiG in June in a 1.72 billion zloty (409 million euros, $515 million) joint venture to tap the country's shale gas reserves by 2016.