Russia is even prepared to give a loan to Bulgaria for successful accomplishment of the project (2 reactors, first one to be comissioned in 2013, second in 2014).
However, 11 private banks have refused to finance the project under pressure of ecological organisations who claim that Belene plant might be potentially dangerous for the environment because of it's location in seismically unstable region near the border with Romania. The construction of the plant was initiated in 1985, but soon after that stopped because of the protests. Bulgarian Academy of Science oficially confirmed that nuclear power plant construction in that region might be potentially dangerous.
But the construction was resumed in 2006, operated by two companies - Russian Atomstroyexport and French-German Areva Group.
Russian ecological organisation are concerned about Russian participation in the project and the willing to offer Bulgaria a loan which has quite low possibility to be returned - especially in case something happens tot he plant even before it might get launched.
It might seem that Russia is investing money in potentially "failed" projects, however, in case with Bulgaria Russia has much more interests in cooperation with this country - a Southers gas pipe branch is just about to be built to lead Russian gas to European consumers via Bulgarian territory. Taking this interest into concern, one might think that Russia is investing into good relations with Bulgaria.