Friday, May 7, 2010

Small Modular Reactors:

Is Small Beautiful?--Time Will Tell

The buzz word of the year in the nuclear industry seems to be "small reactors." Having been involved in discussions of small reactors since my DOE days, I am both pleased and concerned about the hype.

I am pleased because I think there are some real potential advantages to small reactors, particularly for remote and small-grid applications. Potential advantages have also been cited for some larger-scale applications, including the ability to limit the capital requirements by building units incrementally, the ability to refuel one module at a multi-module site without shutting down the whole site, and (depending on the technology), some possible safety advantages.

However, I am concerned lest we expect too much of a technology that hasn't yet been proven. I was therefore pleased to see a reasonably balanced, albeit all to brief, discussion on "Downsizing Nuclear Power Plants," in the latest issue of IEEE Spectrum. I was also glad to see my grad school classmate, Andy Kadak, quoted prominently. The article outlines some of the well-known advantages of small, modular reactors (SMRs), but emphasizes that the installation costs may be as much as, or even more than, those of larger reactors. The advantages may lie more in the savings in financing costs if the plants can be built faster than in differences in the actual capital cost. There is also the fact that the utility's outlay per plant is smaller, so the utility is less likely to have to "bet the company" on the commitment to build.

The article was not intended to be encyclopedic on small reactors, so I cannot fault them, but their discussion of some of the available technologies was brief and incomplete. It should be noted that the designs mentioned vary from those that may indeed be close to "shovel ready" to those that still require significant development. While there are some small reactor proposals that rely on the technologies we know the best, and could conceivably be built soon, most of the design concepts are very different than existing reactors, raising the possibility of many unknowns that could slow or derail progress. At a minimum, the time needed for their development and deployment is clearer considerably greater. In addition, the more innovative small reactor designs will also raise new regulatory issues to be dealt with by the Nuclear Regulatory Commission, so licensing the first of these may not be a quick or easy process.

None of this is meant to throw cold water on the idea of SMRs. I am a big believer in diversity of energy supply for many reasons. I think the future energy mix could well involve both large and small SMRs. But I always worry when the newest idea takes on the trappings of being the "silver bullet." This is true whether that newest idea is fusion, carbon sequestration, renewables, smart grids--or, among reactor technologies, small modular reactors.

Therefore, within the nuclear community, I worry a little that SMRs are beginning to dominate the dialogue. I do not think the proponents necessarily intend it, but the general public sometimes doesn't hear all the nuances, and wants to turn immediately to building the better mousetrap, not realizing that the better design is still a paper reactor. (Sorry for the mix of metaphors here, from silver bullets to mousetraps, to paper reactors.)

The solution to this situation is not to let uncertainty stop us, but to assure that we don't start cutting off other options in anticipation that we have found the silver bullet.



  1. Gail the principle benefit of small reactors is the potential for factory based production. The full cost and productivity benefits of small reactors will not be realized until the emergence of Molten Salt reactors which will be simple and cheap to build in factories, while offering huge advances in nuclear safety, and fuel efficiency.

  2. Gail - as one of the longer lived proponents of small reactors (see, for example I feel reasonably well qualified to comment.

    You are correct that the "actual capital cost" might be higher on a per unit power output basis than a larger plant, but that measure is not very important to many customers. What matters more to them is the total cost, including financing and the cost of supplying power during the period when the project is being planned licensed and built. If the time to market can be shorter for smaller, simpler plants, financing cost savings may overwhelm any scale diseconomies.

    In addition, there is a well understood principle in manufacturing that the costs drop on a relatively predictable basis as the cumulative unit volume of any particular product doubles. Often called a "learning curve" there is more to it than that including the ability to amortize one time design and tooling costs over a larger number of units.

    Finally, it is not accurate to imply that smaller reactors are anything new. We started the whole nuclear enterprise with smaller systems and worked our way up to larger ones. Though the light water variants in the small reactor field obviously have a lot of commercial and naval experience to build on, we should not forget that the very first reactor to power lightbulbs was a liquid sodium cooled reactor called EBR I. EBR II, a pool type sodium cooled fast reactor that is quite similar to PRISM, 4S, and the ARC reactor operated for at least a couple of decades before being shut down.

    Rod Adams
    Publisher, Atomic Insights