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Why Small Modular Nuclear Reactors Won’t Help Counter the Climate Crisis

Why Small Modular Nuclear Reactors Won’t Help Counter the Climate Crisis

One in a series of articles on “None of the Above

Small modular nuclear reactors, or SMRs, are designed to generate less than 300 megawatts of electricity – several times less than typical reactors, which have a range of 1,000 to 1,600 MW.  While the individual standardized modules would be small, plans typically call for several modules to be installed at a single power generation site.   

The nuclear industry and the U. S. Department of Energy are promoting the development of SMRs, supposedly to head off the most severe impacts of climate change. But are SMRs a practical and realistic technology for this purpose?

To answer, two factors are paramount to consider – time and cost. These factors can be used to divide SMRs into two broad categories:

Light water reactors based on the same general technical and design principles as present-day power reactors in the U.S., which in theory could be certified and licensed with less complexity and difficulty.

Designs that use a range of different fuel designs, such as solid balls moving through the reactor core like sand, or molten materials flowing through the core; moderators such as graphite; and coolants such as helium, liquid sodium or molten salts.On both counts, the prospects for SMRs are poor. Here’s why.

Economics and scale

Nuclear reactors are large because of economies of scale. A reactor that produces three times as much power as an SMR does not need three times as much steel or three times as many workers. This economic penalty for small size was one reason for the early shutdown of many small reactors built in the U.S. in the 1950s and 1960s.

Proponents of SMRs claim that modularity and factory manufacture would compensate for the poorer economics of small reactors. Mass production of reactor components and their manufacture in assembly lines would cut costs. Further, a comparable cost per kilowatt, the argument goes, would mean far lower costs for each small reactor, reducing overall capital requirements for the purchaser.

The road to such mass manufacturing will be rocky. Even with optimistic assumptions about how quickly manufacturers could learn to improve production efficiency and lower cost, thousands of SMRs, which would all be higher priced in comparison to large reactors, would have to be manufactured for the price per kilowatt for an SMR to be comparable to that of a large reactor.

If history is any guide, the capital cost per kilowatt may not come down at all. At a fleet-wide level, the learning rate in the U.S. and France, the two countries with the highest number of nuclear plants, was negative – newer reactors have been, on the whole, more expensive than earlier ones. And while the cost per SMR will be lower due to much smaller size, several reactors would typically be installed at a single site, raising total project costs for the purchaser again.  

Mass manufacturing aspects

If an error in a mass-manufactured reactor were to result in safety problems, the whole lot might have to be recalled, as was the case with the Boeing 737 Max and 787 Dreamliner jetliners.

But how does one recall a radioactive reactor? What will happen to an electricity system that relies on factory-made identical reactors that need to be recalled?    These questions haven’t been addressed by the nuclear industry or energy policy makers –  indeed, they have not even been posed. Yet recalls are a predictable and consistent feature of mass manufacturing, from smartphones to jet aircraft.The problem is not merely theoretical.

One of the big economic problems of pressurized water reactors, the design commonly chosen for light water SMRs, including the NuScale design, which has received conditional certification from the Nuclear Regulatory Commission, was the need to prematurely replace the steam generators – the massive, expensive heat exchangers where the high-pressure hot water from the reactor is converted to the steam that drives the turbine-generators. In the last decade, such problems led to the permanent shutdown of two reactors at San Onofre, in Southern California, and one reactor at Crystal River, in Florida.Several SMR light water designs place steam generators inside the reactor vessel (Figure 1). Replacement would be exceedingly difficult at best; problems with the steam generator could result in permanent reactor shutdown. 
We have already seen problems with modular construction. It was a central aspect of the design of the Westinghouse AP1000 reactor, yet the AP1000 reactors built in the U.S. and China have had significant construction cost overruns and schedule delays. In 2015, a former member of the Georgia Public Service Commission told The Wall Street Journal, “Modular construction has not worked out to be the solution that the utilities promised.”

March 25, 2021 - Posted by | Uncategorized

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