George Monbiot has a thoughtful post over at The Guardian reconsidering his longtime opposition to nuclear power. Among other things, Monbiot found himself swayed by a recent report from the Finnish radioactive waste authority (oh yes) suggesting that long-term storage of nuclear waste could, in principle, be carried out safely. And, while he's still in favor of using both renewable power—solar, wind, geothermal, biomass—and increased efficiency to do the bulk of the work decarbonizing the economy, he argues that these sources likely need to be complemented by either nuclear power or (if it can be made to work) natural gas or coal plants that sequester their carbon underground:

So why contemplate nuclear power at all? Why not, as Merrick suggests, decarbonise our economy solely through energy efficiency and renewable power? In principle it could—just about—be done, as Mark Barrett at University College London and the authors of the ZeroCarbonBritain report suggest.

But as you load more renewable energy onto the grid, it becomes more expensive and harder to manage. As Mark Barrett, ZeroCarbonBritain and the German government have shown, you could have a balanced, reliable electricity supply consisting largely of renewables. But the balancing costs will rise a good deal as the penetration of renewables increases beyond, say, 60 or 70%. It is also worth noting that some of the more ambitious renewables proposals will take at least as long to implement as a new nuclear programme. We could decarbonise the electricity supply quicker and more cheaply if we complement renewables with other sources.

Conceptually, I think this is quite right. The main question about relying on nuclear power for carbon-free energy is the fact that new plants are hugely expensive (and current projects are being plagued by cost overruns and material bottlenecks). One new study pegged the generation costs of new power from nuke plants at 25 to 30 cents per kilowatt-hour—triple current electricity rates. But, as Monbiot notes, any preferred low-carbon alternative—renewable power, efficiency improvemnts—will eventually hit diminishing returns, which is why we need to keep a wide range of options open. (Indeed, this is why even Joe Romm, no great fan of nuclear power, expects nukes to provide one of his 14 "stabilization wedges," solutions that will help the world keep atmospheric carbon concentrations at manageable levels.)

--Bradford Plumer