### Nuclear power: The only available solution to global warming

New fission technologies not only eliminate the concerns about safety and waste that plague today's reactors; they can also consume existing nuclear waste.

Global warming, energy independence, water scarcity and third-world economic growth are all amenable to a common, safe, clean, cost-competitive and field-tested nuclear solution. Why isn’t this solution universally embraced and implemented?

I suggest two reasons. First, we humans respond much more strongly to dramatic events, like earthquakes, violent weather and terrorist acts, than we do to steady-state threats, such as auto accidents, medical errors and coal particles. At a cost of $4 trillion, we started two wars in response to the terrorist attacks of 9/11 that killed 2996. The death tolls in the US from auto accidents (30 000), medical errors (44 000–200 000), and coal dust (13 000) are not only higher, but also perennial. The gradual character of carbon dioxide emissions and global warming is elevating our “boiling frog” tendencies to an entirely new scale of danger. Although the problem may not excite us, our pot is warming so quickly that we must leap to survive. A measure of the magnitude and urgency of this challenge can be found in Bill Gates’ summary of his wonderful TED lecture on this topic: Despite the time, effort and money he has devoted to new vaccines and seeds, if he could be granted a single wish for the coming decades, it would be for a practical, CO2-free energy source. That explicit prioritization reflects his awareness of an especially unfortunate feature of warming, that its burden falls most heavily on the politically voiceless poor, and less heavily on those with the means to address the challenge. The disparity adds to our inertia. The second reason lies in deeply entrenched myths (which for my purposes I shall define as untruths breeding complacency), rooted in unrealistically high expectations for renewable energy and unrealistically negative expectations for nuclear power. Criticism of nuclear power focuses on history and ignores dramatic advances in fission technology. This incomplete picture gives rise to myths that conflict directly with the assertions of Gates and of John Parmentola, the US army's director of research and laboratory management: that nuclear fission is the only “practical” solution in view. The remainder of this essay comments on Gates’ criteria for “practicality,” and examines the factors of availability, reliability, cost, scale, safety, proliferation and waste. The good news is that new fission technologies make fission clean, safe, competitively inexpensive, and resistant to terrorism. Moreover, they solve the nuclear-waste challenge. One technology claims to reduce the high-level waste output of a typical power plant from 20 tons per year to a few kilograms. American startups are pursuing commercialization, but much of the action is in other countries, notably China and India. Gates and Parmentola also emphasize the urgency for halting CO2 emissions. In my view, the following six widespread and paralyzing myths must be addressed. Myth #1: Wind and solar can do it Renewable sources, like wind, solar, and tide, emit no CO2, and that’s undeniably good. While the discussion of renewables often focuses on cost, it is power density and intermittency that conspire with cost to prevent these technologies from providing adequate solutions. As Gates puts it, technologies for renewable energy represent energy farming. Because the intrinsic power density of renewable sources is orders of magnitude lower than that of hydrocarbons and nuclear processes, large tracts of land are required to reap even modest quantities of power. Even if large tracts of land, such as those in the Sahara or the American Southwest, are employed, the electricity produced is inherently intermittent, and must be stored and transported. For example, Gates estimates that all the world’s existing batteries can store only about 10 minutes of electricity consumption. Also, because land is not available near population centers, transport such as high-tension towers must be provided. While the relative cost of renewable sources is improving, cost still represents a disadvantage of several hundred percent that has been compensated by government subsidies. Subsidies might continue, but as Hargraves emphasizes in his extensively researched book, Thorium: Energy Cheaper than Coal , the prospects for eliminating CO2 emissions are greatly improved if the alternative power source is cheaper than hydrocarbons. The high energy density and availability of coal make it misleadingly attractive. Hargraves concludes that at least one of the next-generation breed-and-burn fission technologies can produce electricity for about$0.03/kWh, making it cost-competitive, even with coal. The intrinsic safety and relative simplicity of the coming generation of breed-and-burn fission reactors makes them significantly less expensive than those of the present generation.

Myth #2: Nuclear is unsafe

There are two safety issues in the context of nuclear power: meltdown and terrorism. Both are essentially eliminated by next-generation fission technologies.

Concerns raised by incidents at Three Mile Island and Chernobyl were seriously aggravated by recent events at Fukushima. Such dangers are not intrinsic to fission, but stem from military priorities favoring fuel rods comprised of metal-clad ceramics. Ceramics conduct heat poorly, and active cooling (powered externally) is required to prevent overheating, melting and rupture of the cladding. Molten-salt reactors are qualitatively different. First, the exploiting the molten state leads to an inherently safe reactor design, since no additional melting is possible. More specifically, the far superior thermal conductivity of molten salt eliminates the need for active cooling. At any time and without any external power, the reactor can be drained, by gravity, into a subterranean vessel in which passive cooling suffices. Such reactors are termed “walk-away” safe. A molten-salt reactor ran successfully and without incident at Oak Ridge National Laboratory for four years.

High-level wastes produced by fission are unavoidable, but they are only a tiny fraction of what we call nuclear waste. The complete burning of nuclear fuel in molten-salt reactors provides all the benefits of reprocessing, which has permitted France, for example, to produce about 80% of its electricity from fission for decades, without theft of fissile material by terrorists, although Greenpeace did block a plutonium shipment. Because next-generation reactors integrate breeding and burning into a single process, fissile material does not exist outside the reactor, where it is both hot and diluted, thereby reducing the risk of theft significantly below even that of reprocessing.

Myth #3: Nuclear waste remains an unsolved problem

As the term “breed-and-burn” suggests, next-generation fission technologies are related to and provide the benefits of reprocessing. An independent benefit of molten-salt technologies is that the fissile material can remain in the reactor until it is completely consumed, thereby producing dramatically less waste. In today’s solid-fuel reactors the fuel is clad in metals that can tolerate only a limited amount of neutron bombardment, necessitating removal of the fuel long before it is fully consumed. This distinction is the basis of the claim by the MIT-based startup, Transatomic Power, that waste production can be reduced from tons to kilograms, increasing by a factor of 30 the energy obtained from a given quantity of fuel. Refueling frequency is also reduced in molten-salt reactors by the continuous removal of neutron-absorbing xenon, whose accumulation in solid-fuel reactors also reduces the time that fuel can remain in the reactor.

A bonus, but not a surprise, given the connection between breed-and-burn reactors and reprocessing, is that some new reactors can consume existing nuclear waste—both depleted and spent fuel. In this way, next-generation fission can solve the waste problem created by present-generation fission.

Myth #4: Fission may provide electricity, but it neither fuels transportation nor provides clean water

Fission produces cheap heat, which is broadly useful. In the present context, the cost-effective heat produced by fission is symbiotic with two highly developed technologies that address two of our most critical challenges, CO2-free transportation and seawater desalination.

Transportation consumes a large fraction of the energy budget. Its fractional share is approaching that of industry, which is about twice that of both residential and commercial energy consumption. Since fission reactors are unlikely to be placed in cars and trucks, in what sense can fission contribute to CO2-free transportation? The answer is the synthesis of ammonia. NH3 synthesis is among the most promising exploitations of heat from fission. NH3 can be viewed as an especially effective medium for hydrogen storage and delivery. The infrastructure for NH3 production and distribution is already widespread. NH3 has about half the energy content by weight of gasoline, but its much lower cost gives it a price-performance advantage. Most importantly, NH3 burns to form air and water:

4NH3 + 3O2 = 2N2 + 6H2O

Fission also offers a choice between electrically powered reverse osmosis and traditional distillation as means to produce potable water. Distillation can use fission-produced heat directly, whereas reverse osmosis is very energy demanding, and can use fission-produced electricity. Either way, the value of potable water is rising rapidly, and will benefit directly from cheap clean power.

Myth #5: Nuclear installations are large, expensive and problematic to site

The greater efficiency of molten-salt reactors makes them smaller for a given capacity. More importantly, they operate at atmospheric pressure, which eliminates both the threat of explosion and the need for a large containment structure, the visual signature of today’s fission plants. In combination with the pervasive relative simplicity of molten-fuel reactors, elimination of the containment structure renders molten-salt facilities relatively small and inexpensive. Such reactors also lend themselves to factory manufacture, further reducing their cost. The original molten-fuel reactor was intended to power airplanes. In the present context, the efficiency, reduced size, and guaranteed safety of next-generation fission plants combine to reduce the NIMBY (not in my backyard) resistance to their siting.

Myth #6: Nuclear requires lengthy development (new game changer needed)

Writing in the February 2013 issue of Physics Today, John Parmentola called for the invention of a game-changing fission technology. Correspondingly, Gates calls for hundreds of startups pursuing different variations on the common theme. Gates is involved with one such company, TerraPower, which will commercialize an innovative solid-fuel breed-and-burn technology.

The call for startups and game changers reveals the great irony of this context: that arguably the most promising of the breed-and-burn technologies is not at all new. As mentioned above, the molten-salt thorium reactor was developed at Oak Ridge National Lab in the 1960s, where it ran successfully for four years.

A measure of the significance of the Oak Ridge effort is the conviction and enthusiasm of the Oak Ridge lab director, Alvin Weinberg. His zeal for the intrinsic safety and other virtues of the molten-salt reactor, now called LFTR (lithium-fluoride thorium reactor), was not politically welcome, and led to his firing by President Nixon in 1973. Weinberg devoted the rest of his life to the promotion of LFTR; the Weinberg Foundation continues his mission.

A contemporary proponent of LFTR, Kirk Sorensen, leads the startup Flibe, which is focused on LFTR commercialization. The MIT-based startup Transatomic Power recently won an ARPA-E competition as part of its efforts to commercialize a LFTR-related technology that will burn “spent” fuel or uranium, at least initially.

Where the action is

As David Kramer reported in the November 2012 issue of Physics Today, enthusiasm for nuclear power has waned in the US. The Fukushima events have led to similar declines in Japan and Germany. Fortunately for the world, others are moving forward; consider fission facilities in China:
• 14 operational
• 27 under construction
• 51 planned
• 120 proposed
• 212 total

The central assertion here echoes that of both Gates and Parmentola: nuclear fission is the only known technology capable of bringing CO2 emissions under control. My hope is that greater awareness of the benefits promised by coming fission technologies will debunk the myths currently stalling public and private investment, and reverse the unfortunate trend in the US, Japan and Germany.

Art Williams is a condensed-matter theorist, retired from IBM's Thomas J. Watson Research Center after 30 years there. Watson is located near the Indian Point nuclear-power facility. Living and working near Indian Point continues to motivate him to learn about the issues surrounding nuclear power. He is now a registered and practicing patent agent.