What do you call it when you are both excited and pessimistic about something at the same time? Well whatever the word is, that’s what I feel now. Rolls-Royce has announced that it plans to build so-called small modular reactors (SMRs), which could be in operation by 2029. These are small nuclear reactors that would sit on a 10 acre space, about 1/16 the size of a standard reactor. The Rolls-Royce design is not the first one. The US has been developing SMRs of varying sizes, up to 300 MW capacity, and China and South Korea are developing SMRs.

Actually – small nuclear reactors are not new. We have been using them on nuclear submarines and other vessels for years. What is new is commercial SMRs for grid power. I could not find any in operation currently. The US company NuScale, has approval for a design and could be operational by 2026. They estimate the electricity costs at $65 per MW hour, which is not far from the current costs of solar at $60, and offshore wind at $50. Of course, wind and solar prices are dropping, but the hope is that economies of scale will also drop the cost of SMRs.

There are also potential advantages of SMRs over renewable and traditional nuclear power plants. Regarding renewables, while the prices are dropping now once we saturate the grid with renewable energy, something like 30% penetration, in order to increase the grid share of power from renewables you need some combination of two things, grid storage and overcapacity (sharing energy across the grid). The latter also requires a massive grid update. So the effective cost of renewables will start to skyrocket. The solution is to make up the rest of our energy infrastructure with on-demand energy sources. We can try to maximize hydroelectric and geothermal (which are geographically limited), but for now that means fossil fuel or nuclear.

So realistically, over the next several decades at least, the real choice we face is not between nuclear vs renewables, it’s nuclear vs fossil fuel – and I think the answer here is a no-brainer (I will return to this below).

What are the potential advantages of SMRs over traditional larger nuclear plants? According to a US government analysis:

Advanced SMRs offer many advantages, such as relatively small size, reduced capital investment, ability to be sited in locations not possible for larger nuclear plants, and provisions for incremental power additions. SMRs also offer distinct safeguards, security and nonproliferation advantages.

Reducing up-front cost is perhaps the biggest feature. It’s questionable whether or not we have the political will and therefore capital to build massive nuclear plants. For now, it is more cost effective to invest in renewables. Of course, when we get to the point that we hit the limits of cost effective renewables, we will then need to replace and even expand our nuclear profile, and it will be too late to start the process then. We need to start now in anticipation of their future need. SMRs make that much more feasible.

SMRs could be of any type (the term only refers to size – basically 300 MW or less). They could be Gen III or Gen IV designs. I, of course, favor the Gen IV designs which are far more advanced, and offer advantages of their own, such as reduced waste and even burning waste from older plants. They are also much safer by design. Of course, this is an untested technology so everything is some degree of speculation.

But combining Gen IV technology with SMR design is probably the way to go. These plants can be scaled better to need, and are easier to place and defend. In fact, they are small enough to place in underground facilities, hardening them against plane crashes, for example. They are also more modular, so adding capacity is much easier than having to build a massive plant. In operation they also can potentially ramp up and down quickly, even in minutes. And their modular deployment means that entire SMRs can be fired up or shut down as need requires, creating a much more flexible grid.

SMRs can also be brought online much more quickly than larger plants, by the end of this decade. Some argue that that is too late, but that argument is total nonsense. First – it’s never too late to keep things from getting even worse. Further, there is no way we will be totally off fossil fuel for energy production by the time these reactors can potentially come into service. As they come online, coal fired and even natural gas plants can sunset. And again – you will not be shutting these plants down with wind and solar, not without massive grid storage that we don’t currently have and likely will take longer to develop and deploy than SMRs.

So all this sounds great – Gen IV SMR tick all the boxes. They produce large scale clean and carbon free energy, they are scalable, on demand and flexible, and the new designs should be safer, easier to safeguard, and produce less waste (again, even burning existing waste – so they are nuclear waste negative). Processing waste into fuel is expensive, but that technology is rapidly advancing also.

Of course there are many unknowns here because we are talking about future technology. This is being developed, but until we have plants in operation we don’t have any hard numbers on actual cost, performance, and safety. But this is always the case when we are advancing technology. We have to bet on future technology based on the best estimates of appropriate experts. And those experts agree – it is very difficult to achieve zero carbon without nuclear:

Shindell, who was one of the coordinating lead authors on the chapter, told us that it was a rare scenario that met or mostly met the 1.5 degrees limit and didn’t have nuclear power in the mix. “Very few, almost none in fact, can achieve 1.5 without nuclear,” he said. “It’s a very extreme scenario that can do that. And it requires enormous gains in all the zero-carbon sources.”

Here is where there is some wiggle room – it is technically possible to achieve zero carbon without nuclear, it’s just practically not feasible. Now we are getting to the point where I am pessimistic. In this countries we have two main political parties, one largely ignored the science on global warming, and the other largely ignores the science on nuclear energy. The Democratic candidates range from Sanders, who would phase out nuclear quickly, to Yang, who is the only one who would expand nuclear. The others are all weak on nuclear, and would either “wean” off, or not expand or build any new plants, letting existing plants sunset. This is the politically safe thing to say on the left, but it’s not reality.

Without saying so, they are trying to thread a very thin needle, taking the least feasible path to a carbon free energy infrastructure (hiding behind the fact that it is technically not impossible). They do this while simultaneously claiming that climate change has the highest priority. These two positions are mutually exclusive.

There is a strong scientific consensus that the most feasible and likely path to a carbon neutral energy infrastructure includes “some” nuclear. There is only disagreement about how much and in what form. If we want to give ourselves the best change of meeting our climate goals, then we should invest in this new nuclear technology. Gen IV and SMRs potentially answer all the traditional objections to nuclear. At this point we should explore and pursue every option, and let the chips fall where they may. Taking nuclear off the table is extremely risky, with a very small chance of allowing us to meet even the most conservative climate goals. But the political will is just not there.

I have to hope that politicians say what they think they need to say, but then consult experts and do the right thing behind the scenes. Or – private companies take matters into their own hands. If Rolls-Royce, for example, successfully develops a cost-effective SMR that works, it will likely be used. Build it and they will come.