In the green community it's not terribly fashionable (to put it mildly) to favour nuclear power. Despite the support of such luminaries as the developer of the Gaia hypothesis James Lovelock and the British environmental writer George Monbiot, nuclear power is widely regarded as beyond the pale, one of the enemies of the environment rather than one of its friends. We all know the Chernobyl / Three Mile Island history as well as the deep and justified mistrust of large corporations that drives this perception. Some might even say that the term "pro-nuclear environmentalist" is an oxymoron - that it's impossible to be truly "for" the environment if one is not also "against" nuclear power.
Nevertheless, after more than a decade of careful fence-sitting, I've recently come down solidly in favour of nuclear power. What follows is a gentle jeremiad that lays out my reasoning.
Let's start with my two foundational assessments:
1. Global warming is the largest biophysical threat humanity has ever faced. It's caused by anthropogenic carbon dioxide, which makes fossil fuels an enemy of all life.
2. Global warming is not a future threat. The current (rising) level of atmospheric CO2 tells us that the threat has arrived.
It stands to reason that if we wish to mitigate CO2 impacts we must reduce the amount of CO2 we are generating from our energy production. We can do this both by reducing our energy consumption and by finding ways to generate it without adding to the CO2 burden. However, even if we can immediately reduce our energy consumption we must also immediately change our energy mix to one that generates less CO2 overall. The urgency is because of point #2 - immediate threats require immediate responses.
Because of the urgency of the problem, we must use every energy tool at our disposal to cut our CO2 production immediately. Our toolkit must include every low-carbon energy possibility. The current candidates are solar (thermal and photovoltaic), wind, hydro (both conventional and Run of River), tidal power, biomass, geothermal and nuclear.
My decision about where to throw my support is governed by point #2. Because we face an immediate threat, I strongly favour technologies that can have an immediate impact on the energy mix. The more distant the return of a technology or the lower the current level of implementation of a technology, the more of a discount I apply to its value.
The technologies I value most highly, in order of descending priority, are: nuclear; conventional hydro; wind; solar thermal, biomass and solar PV.
I do not think that the dangers of nuclear power outweigh its benefits, especially when considered against the overwhelming threat of CO2. In fact I think the planetary dangers of nuclear power are many orders of magnitude (that's tens of thousands of times) less than the dangers of CO2. See point #1.
The other sources all have various problems. Conventional hydro and solar thermal have limitations in terms of site availability. Solar PV still suffers from cost, land use and intermittency problems. The value of Run of River hydro, geothermal and tidal power are down in the noise at this point due to their currently low actual energy production. The value of wind power could eventually exceed nuclear power, but it will probably take 15 years to get there. We need to take action now, and what we do within the next 5 years will be crucial. See point #2.
Energy efficiency always is the cheapest way to reduce CO2 production, provided we can avoid a rebound effect (aka a "Jevons paradox"). Efficiency should be pursued at least as vigorously as new energy sources.
Nuclear power integrates easily into the existing electricity grid structure, the plant designs are well understood, plants can be built out quickly, and the demonstrated level of risk, compared to atmospheric CO2, is negligible. It's a win, at least until wind is producing 15-20 times its current amount of electricity.
My conclusion is that if we do not build out large amounts of nuclear power, we have no hope of abating CO2 production for at least the next 10 years. See point #2.
Now, all the foregoing depends on us (the global "us") doing enough in the next 5 to 10 years to tip the rate of production of CO2 onto a downward slope. If we cannot create the will to do that, then this entire discussion is moot. Personally I don't think we'll get enough public consensus or freedom from corporate influence to make that possible. So where I ultimately come from on all this is:
Due to the structure and functional requirements of our civilization none of this is possible. That makes these discussions the equivalent of a dog gnawing on a bone: it's something fun to do while we wait for the next meal, but it isn't going to save the world. So in light of that, we should each do what we think is appropriate: try to save the world, retreat from it, get on with raising our families, meditate, search for higher meaning, or just try to have a bit of fun.
The world ends in every moment, then begins again in the next. Sic Transit Gloria Mundi.