Gas has lower CO2 emissions and the advantage over coal that it can better supply peak loads. At that point in time Russia was also seen as a reliable cheap sup

Gas has lower CO2 emissions and the advantage over coal that it can better supply peak loads. At that point in time Russia was also seen as a reliable cheap supplier of it, as the UdSSR has been since the 70s before. It's unlikely that coal could have been replaced with new nuclear. It would have probably been an EPR from back then Framatome and Siemens. Construction of the EPR in Olkiluoto started in 2005 and just finished recently. Keeping old nuclear reactors running and shutting down coal plants instead would have been possible though, but didn't have backing in the population.