We should be putting insane amounts of money into fission research (as well as fusion research, and renewables). Our current fission reactors are based on 1950s designs, because nobody's wanted to invest. The priority has to be to eliminate CO2 emissions. If nuclear can help with that, it just has to be on the table as an option for generating baseload power. (Some private individuals like Bill Gates is funding new, alternative designs but it doesn't feel like enough).
Regarding new nuclear power stations, it is clear that the UK government was not prepared to invest. And as a result it has turned to EDF to build the new facility at Hinckley Point in Somerset with additional funding from China. And we have just been informed that the cost is increasing and the timetable slipping.
Meanwhile, the government has had to guarantee a price for the electricity which is significantly higher than the reducing costs of renewables.
The holy grail is nuclear fusion which is still very much in the experimental stage. Fusing Hydrogen into Helium, with the resulting loss of mass requires a massive amount of energy to get the right temperature and pressure in order to create the conditions for fusion to take place.
It has been done but only momentarily and requiring far more energy in than out.