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Small Fusion Could Be Huge C OMMERCIAL POWER FROM NUCLEAR FUSION is 30 years away. We know this because the fusion-energy research community has been saying so for 50 years. If fusion energy ultimately works, its benefit to humankind is virtually impossible to overstate. The nuclear energy release is about four million times greater than the chemical energy released by burning coal, oil, or natural gas, and for that reason it requires very little fuel. Sixty kilograms of fusion fuel—which one strong person could physically carry into the power plant—would power a city of a million for a year. It would take 400,000 metric tons of coal to do the same. On top of that, the fusion reaction produces no carbon emissions, nor any other pollutant. The reaction works by joining, or fusing, nuclei of hydrogen-2 (or deuterium) and hydrogen-3 (tritium) together to make helium-4 (a harmless and useful gas) plus a neutron, which then interacts with lithium in a way that “breeds” tritium for subsequent fusion reactions. The inputs, deuterium and lithium, are both present in seawater in quantities that would last millions of years at least. In a binary black-hole system, the black holes spiral inward and eventually merge into one, emitting gravitational waves in the process. Observations of this process were reported for the first time earlier this year. CREDIT: Simulating eXtreme Spacetimes (SXS) project However, according to recent computer simulations, those elements would be ejected en masse during neutron-star mergers. New research even suggests that a nearby neutron-star merger that took place shortly before the formation of our solar system may have gifted our future planet with a modest excess of these valuable elements. Then the two neutron stars combined into a single black hole that has since wandered away across the galaxy. The world’s grandest fusion project to date is an international collaboration called ITER that comprises a massive reactor under construction in France. Once finished, it will be an experimental platform for demonstrating a sustained fusion reaction that generates more power than it consumes, similar to what goes on at the core of the sun. It was originally scheduled to come online this year at a cost of $12 billion, but its director-general recently stated that it would not be finished before 2025—and for no less than $20 billion—producing a net energy gain no earlier than 2035. The U.S. share alone is now expected to grow from $1.1 billion to closer to $5 billion. And that’s just for a fusion experiment—the precursor to an actual power plant. While ITER is a major step toward proving the feasibility of fusion, many scientists and energy-policy experts believe it is important to Fryer believes there is much to learn from neutron-star mergers and their gravitational-wave emissions in terms of the evolving population of black holes, production of heavy metals, and extreme physics. He is currently working to identify observable events that would sharpen human understanding of the unobservable structure and dynamics of neutron-star interiors. He is also preparing to use merger statistics, as they roll in, to help resolve a longstanding ambiguity concerning the cutoff mass above which stars are destined to become black holes instead of neutron stars. His recent publications lay the groundwork for these advances. But beyond pure science, Fryer’s research is a matter of national security. In addition to neutron-star collisions likely being the ultimate supplier of key national-security materials, including uranium, their explosive nuclear dynamics are applicable to nuclear-weapons research. And many of the Los Alamos scientists who work with Fryer on astrophysical problems subsequently join him and others on essential national-security computations as well. — Craig Tyler Cutaway view of an imploding plasma liner (blue), formed by 60 inward-directed plasma jets, as it engages a magnetized plasma fuel target. (Plasma is hot, ionized gas.) Copyright HyperV Technologies Corp. 2016. 1663 July 2016 3