Small Modular Reactors A Window on Nuclear Energy An Energy Technology Distillate from the Andlinger Center for Energy and the Environment at Princeton University Contributors Alexander Glaser, M.V. Ramana, Ali Ahmad, and Robert Socolow Table of Contents Article 1: Introduction Article 2: Small Modular Reactor Families Article 3: Safety Article 4: Linkages to Nuclear Weapons Article 5: Siting Flexibility Article 6: Economics Article 7: Policy Appendix: Key Concepts and Vocabulary for Nuclear Energy Biographical sketches of contributors and their disclosures are available at http://acee.princeton.edu/distillates. The contributors would like to acknowledge the helpful feedback from John Balkcom, Robert Goldston, Mark Holt, Thomas Kreutz, Granger Morgan, Robert Rosner, Mycle Schneider, Tatsujiro Suzuki, and Frank von Hippel. The Andlinger Center for Energy and the Environment is grateful to the High Meadows Foundation, the Nicholas Family, and an anonymous donor whose gifts are helping to advance public understanding of critical issues related to energy and the environment through this Energy Technology Distillate. Current revision: June 2015 1 Article 1: Introduction Nuclear capital cost The future of nuclear power over the next few scenarios achieve their target while phasing out decades is murky. In the United States and other nuclear power, relying on other low-carbon energy $7,000/kW Gas wins Nuclear wins industrialized countries, a looming question is what strategies – notably, renewable energy, fossil fuel use will happen when the current nuclear power plants without carbon dioxide emissions (“carbon dioxide $5,000/kW Gas winsare retired. Of the 99 currentlyNuclear functioningwins U.S. capture and storage”), and energy demand reduction. nuclear power plants, all but four have been operating Alongside these questions about quantity and share for a quarter century or more; the nuclear plants of of nuclear electricity are questions about reactor size Gas France and Japan are only about a decade younger. $3,000/kW Nuclear wins and type. Two reactor types—the pressurized- and wins Will these be replaced by new nuclear plants, or boiling-water reactors—have been the primary choice have new nuclear plants become too costly in these U.S. Henry Hub (Feb 2015) for the current global nuclear power fleet, constituting countries?E.U. imporCouldt (Feb the 2015) cost barrier be overcome by a over 80 percent of all operating reactors. Their typical new generationJapan of nuclearLNG impor plants?t (Feb 2015) In China and some power capacity (the rate at which they can produce 0 other5 industrializing10 15 countries,20 25 a central30 question is electricity) is approximately 1,000 megawatts, Natural howgas price much ($/mmBTU) nuclear power the country will build. Today, which is also roughly the size of most modern coal nuclear power provides about 10 percent of the Shows how much a carbon tax of $100 per ton power plants, and global capacity is equivalent to world’swould increase commercial the economic electricity. viability of This percentage has 350 of these plants. Both of the dominant types are beennuclear falling; power compared its historic to natural maximum gas. of 17.6 percent was called “light-waterTypical integral reactors,” pressurized-water using ordinary reactor (light) in 1996. Some scenarios for the future mix of energy water for removing the heat produced in theelectricity reactor sources show a continuation of the current steady and uranium for fuel.containment Alternatives building have long been decline of global nuclear power, and some show consideredpressure and the many contenders come in varied an expansion, usually driven by rapid uptake in the vessel types and sizes. Untilsteam recently, the discussion has developing world. generator turbine been largely about alternatives gtoenerator the light-water Two scenarios where nuclear power continues to reactor that keep the size at approximately 1,000 grow,Weapons but that material nonetheless per year are very different from megawatts. More recently,pump the debate over the future each other, are presented in the International Energy of nuclear power has included greater attention Agency’s World Energy Outlook 2014. The “Current to reactor size—specifically whetherwater reactors in with water out Policies” scenario projects that by 2040 global a substantially smaller power output are a better condenser production of nuclear electricity will have risen by choice. This newernuclear debate core about size is the subject of 60 percent relative to 2012, but nuclear power’s this Energy Technology Distillate. share of total electricity will have fallen to 9 percent. By contrast, the About“450 240kg Scenario” plutonium: shows in 2040 an Enough to make 30 weapons expansion in productionat 8kg each by 160 percent and a growth Large versus small of market share to 18 percent, driven by a seven- fold expansion of nuclear power, relative to 2012, in 200 megawatts the developing world. As the appearance of “450” 1,000-megawatt pressurized waterin reactor its name indicates, the latter scenario involves a decrease in carbon dioxide emissions with the aim of A small reactor may allow siting stabilizing the concentration of carbon dioxide in the where a large one 1,000 megawatts atmosphere at 450 parts per million in 2100, only is unsuitable, or 50 parts per million higher than today. Global carbon a cluster of small dioxide emissions in this low-carbon scenario fall from reactors could substitute for a large 32 billion tons in 2012 to 19 billion tons by 2040, one. whereas emissions rise to 46 billion tons in 2040 in the “Current Policies” scenario. An increasing role for nuclear power often appears in low-carbon scenarios, because nuclear fission produces no carbon dioxide, and fossil fuel emissions associated with nuclear power are limited to those associated with reactor construction and auxiliary functions like mining Figure 1.1: Two possible deployments of small and enriching uranium. However, some low-carbon modular reactors. 3 Generally, for a reactor to qualify to be called “small,” As for groups of small reactors being preferred over its capacity must be less than 300 megawatts, that single large reactors, this trade-off involves two is less than one-third the capacity of the reactors that competing economic principles. The disadvantage are common today. Two quite different deployments of smallness is extra capital cost: five 200-megawatt are being considered: 1) as single reactors in power plants will generally cost more to build than locations where a large reactor is unsuitable and 2) one 1,000-megawatt plant built in the same way, as groups, where several small reactors are intended because of what are called “scale economies.” On the as an alternative to one large one (see Figure 1.1). other hand, if the numbers of small plants becomes large enough, unit costs can come down by virtue The one-at-a-time deployment strategy could be of “economies of serial production.” To bring down credible for a country or region with limited total unit costs, large numbers of small reactors might be electricity capacity, where a single 1,000-megawatt built more completely in a factory than large reactors plant would represent too large a fraction of total could be, which is why the generic name for the size national or regional capacity and create systemic risk. alternative to today’s dominant reactor is the “small A rule of thumb is that, to enhance the stability of an modular reactor.” electrical grid, the capacity of no single power plant should be larger than 10 percent of the grid’s total In this distillate, Article 2 outlines a new typology capacity. Over 150 countries have a national installed that allows the more than 50 small modular reactor electricity capacity of less than 10,000 megawatts, designs to be placed in four broad groups. We which would nominally lead them to avoid having any then consider small modular reactors from the 1,000-megawatt reactors. Moreover, grids are often perspectives of safety (Article 3), linkages to nuclear smaller than country-wide. Of course, a country will weapons (Article 4), siting flexibility (Article 5), and be less cautious about building a large reactor if it economics (Article 6). Article 7 concludes the main takes into account its expectations for growth of total text with a brief discussion of policy issues and a table domestic capacity and the option of a regional grid showing some of the small modular reactor designs that includes several countries. For example, the West that are being developed around the world. At the African Power Pool involves 14 countries in the region back is an Appendix, “Key Concepts and Vocabulary that have come together to establish a regional grid for Nuclear Energy,” which should be helpful so as to be able to trade electricity. Although none of background for any reader new to nuclear issues. the individual countries have installed capacities in excess of 6,000 megawatts, with most having under 1,000 megawatts, together their combined installed capacity is close to 12,000 megawatts. 4 Article 2: Small Modular Reactor Families Many small modular reactor designs with distinct about 200 naval reactors (all using pressurized-water characteristics have been proposed or are being reactor technology) are in operation today. Given this developed. These designs vary in their power output, long record of operation and the licensing experience, physical size, fuel type, refueling frequency, siting small modular reactors based on pressurized-water options, and status of development. To create some reactor technology have a substantial head start. coherence out of this variety, we group these small At the same time, there are significant differences. modular reactors into four categories or “families.” Submarine reactors are designed to operate under These categories are distinguished by the main stressful conditions, and this has consequences for objective that guides the design of the reactor, rather many of their components.