Solar maybe NOW is, but this isn't a 5 or even 10 year old problem. And cost effective compared to what? We'll consider sending people to Mars to save humanity but reactors are "too expensive"?
Renewables is more economical than nuclear, so investing in nuclear is a waste of resources. This is also why nobody does it. And no, nobody who hasn't lost their marbles is seriously considering sending people to Mars to save humanity.