Reassessing Nuclear Power:

An interview with MIT Professor of Atmospheric Science Kerry Emanuel

by Matthew Formby

I had the benefit of an interview with Dr. Kerry Emanuel (atmospheric scientist, Massachusetts Institute of Technology)(1) in which he elucidated why global warming is such a significant problem that he and other notable climate scientists(2) argue we must consider nuclear power. The following are notes from that interview. Considering nuclear isn't a matter of overshadowing renewable energy or some form of denialism(3), but a fact that we must act more quickly than we have, or can without using all options. He expressed that the problem is so significant because we remain on track to double emissions this century and potentially to triple them by the end of the century. The effects of inaction could be staggering and we need something more than the status quo to change course. He evaluates three courses of action that should be considered: carbon capture and sequestration, efficiency, and eliminating greenhouse gases. Our options aren't mutually exclusive.


CO2, methane, and other greenhouse gasses are like blankets, and whether or not we add on more, the planet will warm until we take those blankets off or reach a new energy balance. Which is why the first solution Emanuel mentioned is to take CO2 out of the atmosphere and safely dispose of it. This carbon capture and sequestration is something we can do (and are doing in small scales) but there are a few problems. Right now it's expensive, too much so for private industries to adopt wholesale. There's also uncertainty of where to use this technology (it's easiest in exhaust pipes and smokestacks where CO2 is most dense, but that omits many sources, such as motor vehicles). Which makes it uncertain if the technology can be implemented at the level required for our problem.

It really comes down to reduction of energy use and eliminating emissions. (Emanuel 2016)

He mentions that efficiency is an essential option, but we may reach a limit of about a factor of 2 in improved efficiency. We can, and we should, be pursuing more efficient homes, appliances, and lifestyles. But that won't fix the problem alone. Even if the limit Emanuel cites is off, or there is none, demand will always grow with population. And in developing nations where energy access is minimal to begin with, more energy is needed to escape poverty. 

To eliminate emissions he lists hydropower, wind, solar, and nuclear. So why can't we just use the first three, possibly add in geothermal and have a 100% renewable, clean energy grid? We even talked about how Greensburg Kansas(4) recently went 100% renewable, and as the linked article makes note it's almost entirely from wind. The reason we can't all live in cities like Greensburg is a lack of energy storage technology and what he called a 'base load crisis'. The grid, he explained, works a lot like a battery: Greensburg and places like it survive by buying power from other cities when the wind isn't blowing, and selling it back when they have surplus. When there are more than 30% (he cites a range from 20% to 30%) of cities like this he says we run into the fundamental physics of intermittency, which means we will need more base load power to keep the grid stable. The reason Greensburg is considered 100% renewable is because it produces as much renewable energy as it uses throughout the year. Excess power is sold to its neighbors, allowing them to use fewer fossil fuels at the time, but it won't always have that energy, at which times its neighbors sell their own power (which has to be one not suffering from the same cause of intermittency Greensburg) back to it.

Base load Energy

Hydropower can provide some consistent energy, but it's limited. In our interview, he made a point to clarify that hydropower poses its own environmental risks and that it's already largely implemented where it can be. The only remaining clean base load energy is nuclear. This is why, in 2013 and again at COP21 Dr. Emanuel was a part of the same group of four climate scientists speaking out for a review of nuclear power. In the 2013 open letter they beseeched policy makers that 'we cannot afford to turn away from any technology that has the potential to displace a large fraction of our carbon emissions(5)'. With current technology intermittent renewables can't power the world alone, efficiency and carbon capture can help but won't resolve the base load demand, but with nuclear power these become much more feasible. That's it, in one sentence that's why we need to consider nuclear for the climate. But the current industry has given us tragedies, waste, and fear. At this point he presented a few problems with nuclear that need to be understood and addressed: economics, waste, safety and proliferation.

Economics: Time and Regulations

Nuclear power plants are already competitive with coal and natural gas across their lifetime. But they have high capital costs and long construction times. Before going in depth on why construction is slow in the U.S., he noted that fast, safe construction is possible as evidenced in France, which went from almost no nuclear to 80% in just a few years. Long implementation times in the U.S. (notably from regulatory delays) restrict its validity as a response to climate change. He suggested that the underlying cause of the 15 year average construction time is the age of our regulatory system. The system is based primarily on the light water reactor (LWR) technology first developed in the 60s, which has lead to a couple unintended consequences.

The first is that our regulations are due for a change. So even when a safe power plant is designed, proposed and accepted, there's a risk of changes to the regulation of an already delicate process. Trapping the asset from a business standpoint, and making it less likely to use as a response to climate change. The second, and more systemic consequence is that our regulations aren't set up to evaluate next generation reactors that don't rely on the same systems (e.g. water cooling). It makes the process of approval more difficult, expensive, and time consuming. He made sure to note this doesn't mean that nuclear should be less regulated, just that ways to judge new technology are not sufficient. The result is an over-reliance on LWRs which cannot solve or lessen the remaining problems of nuclear. Regulations shouldn't be lessened or removed, but something needs to be done to allow safe use of an essential response to climate change.

Nuclear Waste and Proliferation

I asked Dr. Emanuel if he thinks we should be building more of the established LWR power plants that we have a long history for (and could start immediately), or if we should be looking to a new technology from the next generation of reactors. His answer was a fitting 'both.' The reason has to do with both the time it will take to safely establish the next generation of reactors and the nuclear fuel cycle, which is the link between and an answer for waste and proliferation. The enrichment necessary for LWRs and the energy left behind in waste fuel are both high enough to risk proliferation and other disasters. These risks can be reduced, as explained below, by the next generation of reactors, meanwhile we should be building modern light water reactors to ensure a timely response to climate change. Today's light water reactors are, as he put it 'not your father's, or grandfather's, light water reactors.' Which is to say, they're substantially safer than the older power plants we rely on today.

At the same time he rightly cautioned that 'there is a security risk, it is a problem, and it's not going away.' It doesn't mean that any other source is inherently safe. In fact, in terms of mortality per kilowatt hour produced <in this graph, which was provided by Dr. Emanuel> you can see that no energy source is completely safe, and nuclear power is among the lowest risk. There are a number of factors at play there, and it would be best to look at that separately. For now, we should consider how to make nuclear power safer than it is and Emanuel thinks the key is the next generation of reactors.

Perhaps the most common and valid concern for nuclear power is the prospect of safe guarding nuclear waste for generations. But for newer designs of nuclear reactors, which are capable of using waste fuel or unprocessed uranium, he points out that a "stockpile if done correctly is a resource." This is because the waste is mostly unspent fuel. His emphasis is on managing stockpiles correctly, which should never be taken lightly. But, with the addition of these newer reactors waste could be used as fuel, bringing down how long it must be watched from an order of millennia to a range of around a hundred years. At which time he argues it can be more safely disposed of, reducing both risks of contamination and use in proliferation.

What to do Now

There are two remaining reasons why Emanuel argues for the consideration of nuclear power. The first is that when nations shut down their nuclear power like Germany, in the wake of Fukushima, the result isn't just more clean renewable energy. The short-term consequence of Germany's nuclear shutdown has been increased reliance on fossil fuels as once clean energy is replaced largely by coal  and purchasing more power from its neighbors who do use nuclear. But the other, perhaps bigger reason is rapid construction of light water reactors by, e.g., China, Pakistan and Russia, often sold or leased to developing nations pursuing affordable clean energy to raise living standards. The concerns of proliferation and waste management are greater in these developing nations, especially where conflict is or has recently been. To the issue of managing the fuel enrichment and handling, he poses the solemn question: should we be trusting other nations to be managing these well. It's especially poignant when some argue it can't be done safely in our own nation.

To resolve devastating climate change, and to avoiding added risks presented by purely LWR nuclear power, he proposed two responses to reflect on. The key is to out compete carbon creating fuels, and China and Russia's light water reactors. The first solution is to create and sell hydrocarbon fuels in a carbon-neutral way. The process he outlined relies on two established technologies: hydrolysis and extraction of dissolved CO2 from seawater. These can be combined into hydrocarbon fuel, which would have the benefit for developing nations of making use of existing infrastructure, while remaining carbon neutral, since the carbon has been extracted from the upper ocean, which quickly equilibrates with the atmosphere. While the second response he points to, a proposal from the MIT Nuclear Engineering Department, is to construct offshore nuclear power plants (initially just modern light water reactors) using shipbuilding plants that construct offshore oil rigs now. The infrastructure is there, and a modern regulatory structure can be built around this centralized, standard construction of offshore nuclear. For those concerned about lengthy construction of nuclear, this allows for construction to be ramped up quickly once safe best practices are established. Whatever the course of action we take, we must remember that disregarding a potent source of base load energy will only slow our response to the changing climate.

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