I worked in the field of engineering since 2007. I can surely say that even simply the choice of materials, and metalworking processes mean that the nuclear reactor vessel alone costs like one diesel/LNG power stations.

Steam turbines are bigger, and more expensive than equivalently powerful turbines of a gas-turbine engine, and not to say that gas turbine is also its own source of hot gas.

I think the best option for undeveloped nations is to rent their power generation equipment until they can bootstrap their electric grid, and build proper power stations.