The question is complicated and related to something called ERoEI (Energy Return on Energy Investments). This is the general question on how much energy one must put into getting a source of energy balanced with how much energy you get out. The direct case can be seen with fusion and the break even point where you get net energy out.
As Georg indicates the nuclear power industry has been hugely subsidized in connection with nuclear weaponry. The industry is largely a spin off from plutonium production for weaponry. The stable Pu isotope for weapons is Pu-239, while the other isotopes tend to spontaneously fission. These isotopes are farmed out to the nuclear power industry. So the nuclear power industry is a spin off from the weapons industry. The net financial investment by the United States in nuclear technology is over $10 trillion. We might of course question whether we have recovered this cost, either in financial terms or energy terms. Nuclear accidents are also seriously costly and dangerous, and the industry has some appearances of being like the dirigible industry before 1936. At some point there may be the big nuclear “Hindenburg” incident which might put the kibosh on the whole thing. Events of late come somewhat close to that.
The industry, in part due to its connections with weaponry, has a huge political connection. Unfortunately this has been politics of the far ends of the spectrum, where in the USSR this was with the extreme left communists and in the US this has been associated with the far right that is moving further to the right. The further on either spectrum politics becomes the more it degenerates into a filthy pile of lies. Unfortuantely the economics and politics surrounding nuclear power, mainly with those who run the system, have a long history of being surrounded and mired in mendacities.
The issue with research costs is of course important. The fusion research programs, such as ITER, seem to be a long process of getting closer to a goal, but where the goal also seems itself to recede further away. Renewable energy research tends to get at best second billing, for it is not as “sexy” as “big science” programs with impressive expensive facilities. The funding and political interest is highly skewed in some ways. For instance there is the whole thing about “clean coal,” which is a way of subsidizing the future of the coal industry. However, clean coal makes about as much sense as saying “partially pregnant.” In spite of what the mendacious right wing in the US says, we do have a little problem with $CO_2$ in the atmosphere and the climate perturbation it is generating.
The ERoEI issues then comes into play, where there are people who spend considerable time on this problem. As petroleum becomes less accessible and approaches this peak situation the ERoEI declines. This is a ratio of energy out/energy in, and for a large oil field that is “virgin” the ERoEI is about 25. Currently ERoEI is estimated for oil production globally to be around 10 to 15. Nuclear power is estimated to be a number of values, where about the highest I have seen is 5. The solar, wind, and renewable power systems have a similar ERoEI.