I just finished David Bodansky’s 600+ page tome Nuclear Energy. It’s almost a textbook, but not quite. I don’t know who the intended audience is really. Other than me. Similar genre, broadly, as The High Cost of Free Parking. A comprehensive overview of a technical topic, for those with a long attention span and no fear of numbers. I decided to read the book because of the recent turn toward nuclear power that some environmentalists have taken. There are many publics that react strongly, and negatively, to the idea, but I don’t trust public sentiment to be rational any more than I can manipulate it. Bodansky did an admirable job of remaining neutral throughout the book, on a topic that almost universally devolves into something resembling a religious debate. As a result of this reading, I’m much more positive (or rather, less negative) about nuclear energy than I was before. I think that my position, which I hope can count as an informed one, now closely resembles that of Ralph Cavanagh, as articulated in this debate with Peter Schwartz hosted by the Long Now Foundation.
The main questions I had coming into the book were:
- Can nuclear energy be done responsibly?
- What would it take for it to scale up meaningfully?
- How would it compare in costs and risks to renewable energy sources, if it were done responsibly at scale?
The answers I came away with were that yes, it probably can be done responsibly, and at the scale necessary for it to be meaninful as a long term source of primary power globally. However, if it were to scale up responsibly in the long term, it seems that the associated costs would likely end up being greater than for renewable energy sources. So I guess I’m supportive of having the so-called “nuclear option” on the table, in competition with any other carbon free power source, with the significant caveat that the cost of the nuclear power being considered correspond to a responsible, long term, large scale deployment. The scenario I foresee needing to be avoided is ending up with an unfair comparison, between short-term and/or irresponsible and/or non-scalable nuclear power, and renewables — especially renewables as priced before the solar power industry has obtained whatever economies of scale there are to be had in their niche. One might be able to make a persuasive argument that we need to use nuclear power as a bridge between fossil fuels and renewables at scale, but I haven’t heard that argument made yet.
Great Power. Great Responsibility?
The main objection to nuclear power that I had when I started the book had to do with whether or not it can actually be done safely and responsibly, by which I mean avoiding:
- risk of Chernobyl type accidents resulting in long term damage on a large scale.
- increasing the rate of nuclear weapons proliferation.
- bequeathing a dangerous burden of nuclear waste to our anonymous descendants.
Bodansky effectively convinced me that the rate of weapons proliferation has so far been little influenced by the spread of nuclear power, in spite of Iran’s recent, well publicized, and almost certainly duplicitous attempts to set up their own domestic fuel cycle “for peaceful purposes”. Virtually all the nuclear powers outside the permanent members of the UN Security Council obtained their weapons via so-called “research” reactors, or from the A.Q. Khan catalog. This isn’t exactly comforting news of course. While the world hasn’t shaped up quite the way Tom Lehrer envisioned it…
nuclear weapons have been slowly creeping from nation to nation for the last half century, and to date exactly zero nations have been convinced to give them up once obtained. South Africa is often held up as an example in this respect, but in truth nobody in the outside world forced them to get rid of their six bombs. They made that choice because it became clear that the internal politics of the country were likely to change dramatically, even as the external politics of the world were rearranging themselves. In a similar vein, we are fortunate that the nations which precipitated out of the Soviet Union were able to so amicably reallocate their nuclear arsenals to Russia. It didn’t have to be that way, and we should not draw any optimistic generalization about the stability of the world’s nuclear powers based on these two examples. It’s relatively easy to put policies in place and manage them when one has a stable government. The real test of any safeguards we come up with, for both waste and weapons, will be when nations and civilizations dissolve into anarchy, as they have from time to time throughout history, and as they are sure to do on occasion in the future. What will we do when Pakistan descends into civil war, or when North Korea’s Dear Leader finally dies? As a planet, we are faced with a never ending sequence of tests of our ability to avert a nuclear war. What this book convinced me of is not that the danger of weapons proliferation is small, but rather that it is mostly uncorrelated with the spread of nuclear power. Nuclear disarmament is not a solution to this issue. The knowledge is out there, and we have to live with it to the end of our days. I do not find the position which Thomas Barnett and others within the military establishment take, that nuclear weapons have ruled out the possibility of so-called Great Powers War, to be convincing. Under normal circumstances yes, but under abnormal circumstances, which are more common than we like to imagine, no.
Compared to the prospect of weapons proliferation and the corresponding increase in the chances of a nuclear exchange as time goes on, the dangers of Chernobyl type accidents and the task of managing nuclear wastes seem almost frivolous, but they are not insignificant. With reprocessing to remove the actinides for use as fuel and transmutation of Tc-99 (half-life 211,000 years) and other important long lived fission products, the remaining nuclides in the waste stream are manageable, with none having a half life longer than 90 years, and the important ones (Sr-90 and Cs-137) being closer to 30 years. This highly radioactive waste can be vitrified in borosilicate glass to immobilize it, and stored in a facility which need only be able to survive for a few centuries, not tens or hundreds of thousands of years. As a species we’ve built things that last centuries. We haven’t built anything that lasts more than 10,000 years. The current project at Yucca Mountain is a fool’s errand for a variety of reasons, and a lot of people know it. Even if it’s eventually approved, all the waste stored there will remain retrievable, perhaps for as long as a few hundred years, which is a very good hedge against the current US position that no reprocessing will be done. I have been convinced that in principle, the problem of nuclear waste management, while very expensive and politically intractable, is in theory a technically solved problem, despite the fact that the US is going out of its way not to implement what seems to be the most responsible solution.
I am less confident that it is possible to design a truly idiot-proof reactor, which is what we need if we are going to avoid another Chernobyl. The fleet of reactors which the world currently operates have too many parts, and too many different combinations of possible failure modes, which cannot really be meaningfully tested. Bodansky and the nuclear industry quote small probabilities of failure, and try to make some estimation of how likely it is that a significant accident will happen in a given span of time, based on aggregations of probabilities for all the component parts, and past operating performance. Again, this is a Black Swan problem. The truth is that when probabilities and sample sizes are small, we really have no idea what’s going on, and such analyses implicitly ignore the possibility of malicious or downright bone-headed operators. The Chernobyl accident happened because they turned all the safety mechanisms off, on purpose, for a demonstration of some failsafe (which, duh, failed!). Several people were recently killed in a criticality accident at a Japanese reprocessing plant because they dumped a solution of enriched uranium into a precipitation tank filled with water, which moderated the neutrons and set off a chain reaction. People do dumb stuff, even in nuclear power plants, and even when they aren’t under duress. To be responsible, nuclear power needs to operate safely when manned by morons in the middle of a war zone. Many of the reactors in the Generation IV program incorporate so-called “passive” safety features, usually involving negative thermal feedbacks (e.g. doppler broadening of the neutron absorption spectra), such that loss of coolant accidents result in the reactor shutting itself down, even if nobody does anything. I’m not convinced that any of the designs under consideration meet the morons in a war zone standard, but it at least seems plausible that such a reactor could be designed and built.
That said, it was interesting to read a level headed discussion of just how bad Chernobyl was: pretty bad, as far as conceivable nuclear accidents go. But at the same time, today the radiation levels in most of the evacuated region are comparable to the extra cosmic ray dosage you get from living in Denver above a mile of the atmosphere’s natural shielding, and less than the doses that flight attendants and airline pilots get in the course of their professional duties at 10,000 meters. However, that kind of constant ambient dose isn’t how most people living near Chernobyl would end up getting irradiated. The radionuclides would be chemically concentrated in agricultural produce and livestock, and then consumed at a level much higher than the background. In the grand scheme of things though, one Chernobyl per century, while awful on paper, would probably not have a large impact on humanity, when compared with other things we routinely ignore as a species, like the salinization of our soils through dry land irrigation, or the instability of our climate, or genocide, or malaria, or synthetic biology, or our rotten food system, or the contamination of our drinking water with fracturing fluids from oil and natural gas drilling. Not that we should be ignoring those things, but adding one more thing we don’t care about to the long list is less compelling than holding it up as some kind of uniquely horrible disaster to be avoided. People are for some reason more risk-averse in the context of radiological hazards than other hazards, technological and otherwise. Bodansky conscientiously avoided making the argument that this disparity in our risk assessments implies that nuclear power is safe, as many atomic cheer leaders have done. I suspect this is because there is another logically consistent conclusion: that all of those other things are in reality awful enough that we should avoiding them too. That’s certainly my conclusion.
Issues of Scale
Any meaningful long term source of energy for humanity, even with massive improvements in energy efficiency within the OECD (especially the US), has to scale up to at least tens of terawatts of primary (i.e. thermal) power, and be able to maintain that power output almost indefinitely. In the fullness of time, so far as we understand the universe today, only nuclear energy is capable of this. The question we have to answer is whether we want to manage our own nuclear reactions here on Earth, or whether we want to collect the energy liberated by the nuclear reactions which take place in the Sun.
The average US citizen has a lifestyle which requires about 10 kW of primary power. The average H. sapiens on Earth today uses about 1/5 that much (see Saul Griffith’s excellent talk from this January, or his Watts On presentation here in PDF form). If we can comfortably get ourselves down to 2 kW (and based on my own energy usage, I think we can) and simultaneously bring everyone in Asia, sub-Saharan Africa, the Middle East, and Latin America up to 2 kW, we’re still going to need something like 20 terawatts of power by mid-century, and substantially more if we don’t pursue energy efficiency and and attack profligate use hammer and tongs from now until doomsday. That amount of power is equivalent to roughly 20,000 nuclear power plants, or 50 times the current worldwide nuclear capacity. If nuclear power plants can be designed to operate for 100 years, that means with 20,000 of them, at steady state, we’d be both retiring and constructing roughly 200 nuclear power plants annually, indefinitely. That’s more than one every other day. This is what I mean by “at scale”. If you don’t believe that our power is going to eventually be either solar or (local) nuclear, I recommend watching this talk by Nate Lewis. The other options just don’t scale.
Of course there are other options, but here I am restricting myself to the scenarios which I think we would collectively consider to be successes. Alternatively, humanity globally could assume a very low energy lifestyle, and live everywhere as they do in sub-Saharan Africa and rural Asia today, and as all humans did only a few centuries ago. I think this is unlikely to be regarded as a success by most people, including those in sub-Saharan Africa and rural Asia, who have an intimate knowledge of what that lifestyle looks like, and some idea of what our lifestyle looks like, and seem intent on transitioning to something more like ours. We could also blithely continue burning the coal, oil, and natural gas (as seems to be the “plan” at the moment), but even ignoring climate change we will one day run out of fossil fuels, and be forced to find another energy source. Why not do it now rather than later if we can? Another option — the most attractive and responsible one in my mind — would be a drastic and voluntary reduction of the human population, to something under 1 billion, instead of the peak of 10 billion we’re supposedly headed for. With a pre-industrial human population, I think there would be plenty of room for us and the rest of the earthlings to live in relative comfort and affluence. But that does not appear to be the course we are on. Even if we do manage to peak population this century, and then decline rapidly, we’re still going to have a significant window of time, barring catastrophe, during which we need to provide energy on the tens of terawatts scale. It’s not inconceivable that we could find some new transformative technologies — controlled fusion, or energy efficiency on a currently unimaginable scale — but we should not be taking that as a given in our planning. We must hope for the best, but plan for the worst.
Being able to run our energy systems at this scale for centuries if not millennia is another kind of scalability: temporal scalability. As mentioned above, this is a kind of scalability which our current fossil fuel based energy systems lack. The Sun has another couple of billion years under warranty, so solar power scales through time if we can find a way to effectively take advantage of it. Fission here on Earth is more limited. The US currently sends its nuclear fuel through the reactors once, and only once. Only about 1/3 of the fissile U-235 is consumed that way, before the fission products which are neutron absorbers (aka “neutron poisons”) accumulate to high enough concentrations to shut down the chain reaction. France (which gets about 75% of its power from fission) and many other nuclear power users re-process their fuel, chemically separating out the highly radioactive fission products, and re-forming the actinides (U-235 and U-238, newly formed Pu-239, etc.) into new reactor fuel. This has several consequences:
- You get three times as much power out of a given unit of fuel.
- It greatly reduces the mass and volume of the radioactive waste which has to be disposed of.
- It can dramatically reduce the time which that waste has to be stored, if you store only the short lived fission products, and separate out the troublesome long lived ones for transmutation into something less difficult to deal with.
- It removes a potentially large future incentive for someone in the distant future to go digging around in the waste repository: once the dangerous fission products have decayed away, the remaining fissile actinides potentially become available for weaponization, that is, the waste repository becomes a so-called “plutonium mine”.
So there are a variety of good reasons to reprocess spent fuel. The arguments against doing it are the cost, because it involves a lot of remote-handling facilities to deal with the extremely radioactive material, and the danger of present-day weapons proliferation as separating out the usable fuel necessarily means separating out plutonium, which depending on how the reactor is run, and how long the fuel has been in it, may be weaponized by those with sufficient technical skill. If you believe that the cost and potential weapons proliferation dangers of re-processing are prohibitive, then nuclear power is not really on the table as a serious option for solving our energy problems in the long term.
Re-processing helps with waste disposal issues, and increases the fuel economy by a factor of three, but for nuclear power to really endure, we would need much more than that. We would need breeder reactors like France’s beleaguered Superphénix, which transmute naturally occurring, relatively abundant nuclides (Th-232 and U-238) into fissile fuels (U-233 and Pu-239) by exposing them to intense neutron bombardment from an operational nuclear reactor. Breeding fissile material would result in a truly millennial energy supply.
The Price of Power
So maybe responsible, scalable, long-term nuclear power is possible, and if so it represents a real long term energy option, but it will not be cheap, and it will not be without technical challenges. Renewable power also represents a real long term energy option, if we can figure out how to store intermittently generated electricity or heat efficiently, or how to effectively manage a portfolio of different forecastable, intermittent power sources with minimal storage. That might also turn out not to be cheap, but the scope for cost reduction in renewable energy is potentially large, in part because it is a nascent industry, and in part because there are many different ways of harvesting sunlight. Thus, any fair long-term comparison between renewable and nuclear energy must consider the costs and dangers of reprocessing, the technical challenges of building extraordinarily robust breeder reactors, and the consequences of the accidents, sabotage, and failures which will occur on a timescale of centuries or millennia.
In general, my impression is that the risks associated with nuclear power are more like Black Swans than the risks associated with renewable power, which is a big strike against nuclear. If we’re going to have failures, I’d much rather they were gaussian. I think it’s potentially telling that the person who effectively hamstrung the nuclear industry in the US was Jimmy Carter. He did this by distributing the nuclear regulatory powers among the Dept. of Energy (which he created), the EPA, and the NRC, and giving these disparate bureaucracies different fundamental motivations. They haven’t been able to agree on much since. This is potentially telling because Carter was a nuclear engineer, who worked directly under Hyman Rickover, the father of essentially all production nuclear reactors in existence today (since for better or for worse, our commercial power generating reactors are today still largely based on the ultra-compact submarine reactors Rickover initially designed for the US Navy). I do not doubt that Carter deeply understood the issues surrounding nuclear power and the nuclear industry.
What I’d like to see, ideally, is a leveling of the playing field between renewable energy and nuclear, which will unfortunately mean subsidies for any non-nuclear, carbon free power source which is capable of scaling up to terawatts, in order to overcome the enormous historical subsidies which the nuclear industry has recieved. In the interim, I think it’s an open question whether we should be sympathetic to nuclear power as a temporary bridge as we wean ourselves off coal and oil, scale up solar and wind, and develop economical energy storage technologies. “Temporary” in this context probably means 50-100 years, since that’s how long we might expect a well designed nuclear power plant to last. Enhanced geothermal power (or “heat mining”) is another possible temporary non-renewable emissions free power source we might consider to close the gap. The MIT faculty has made extensive reports recommending the development of both of these power sources, focusing on the next 50 years. In that timeframe I agree that they can both make sense, and that reprocessing is not a necessity, but neither of these power sources as described can be pitched honestly as the same kind of long term solution that renewable energy will be if we can solve the energy storage problem.
Whatever decision we ultimately make about where the nuclear reactions enabling our civilization take place, here’s hoping we make the choice with our eyes wide open.