His company, TerraPower, aims to build a safe, nearly waste-free reactor that won’t contribute to weapons proliferation or climate change
Bill Gates originally became famous (and rich) for co-founding Microsoft; more recently, he’s become better known, through the Bill and Melinda Gates Foundation, as a philanthropist working to improve global health and sustainable economic growth. But Gates is also passionate about fighting global warming, and he’s has become a leading proponent for a revolutionary nuclear reactor design. His firm TerraPower envisions a reactor with, “inexhaustible renewable and eminently economic nuclear energy in quantities sufficient for …10 billion people at United States per capita (consumption) levels.” In short, Gates is on a quest to build a safe, almost waste-free approach that does not contribute to nuclear weapons proliferation.
TerraPower was founded in 2008, 54 years after the first non-weapons application of nuclear energy in 1954 enabled the launching of the nuclear submarine Nautilus. In the wake of that success, Admiral Hyman Rickover, who spearheaded the design and building of the ship’s power reactor, became so influential that he was able to convince the Atomic Energy Commission and Congress to get behind a similar design for civilian power reactors, using uranium as the fuel and water under pressure as the coolant that carried the heat of nuclear fission to turbines that produced steam and electricity. One powerful argument in favor of these reactors was that the fission process created plutonium, which was needed for nuclear weapons.
Unfortunately, as a result of accidents, intractable radioactive waste and high production costs, interest in building these reactors has almost evaporated, especially in the United States, Western Europe and Japan. But it’s not the only reactor design by a long shot: as early as the 1960’s, scientists and engineers at Oak Ridge National Laboratory were working on competing designs, including one that used liquid sodium as a coolant. In the early 1990’s, Lowell Wood, at Lawrence Livermore National Laboratory (he’s been granted more patents than Thomas Edison), made a conceptual leap: the idea of a liquid sodium-cooled reactor that would breed plutonium and then use it as fuel. He and Edward Teller, sometimes called the “father of the H-bomb,” who had always scoffed at the idea that a reactor designed for a submarine would be optimal for a civilian power plant, co-authored a paper that proposed such a reactor. That laid the foundation for the reactor TerraPower wants to build.
Liquid sodium has several advantages over pressurized water. Sodium’s thermal properties provide far superior heat transfer than those of water (the water is pressurized, in fact, to improve heat transfer). It’s also a stable fluid that can be used at an operating temperature of 550 degrees Fahrenheit at ordinary atmospheric pressure, so there’s no need for an expensive containment structure. Pressurized water by contrast, carries a danger of explosion, either from steam or from hydrogen created when water in an overheated reactor oxidizes the metal casing of the fuel rod containers.
Most significantly, and unlike water, sodium does not absorb or slow neutrons produced in fission reactions. That means that as its uranium-238 fuel generates plutonium, the plutonium itself then undergoes fission, generating even more energy. This so-called breeder-burner design would be entirely self-sustaining.
TerraPower envisions the use of natural uranium, depleted uranium, uranium obtained from processed sea water or radioactive waste as fuel. Not only is there little residual waste associated with the reactor, it would not be subject to loss-of-coolant accidents nor would it enable nuclear weapons production; the plutonium does not get separated out and thus is not available for weapons. Another major advantage is that TerraPower’s reactor could in principle run for 50 years without a need to be opened for the addition of fresh fuel or the removal of radioactive waste.
This doesn’t mean that the TerraPower reactor is ready for market. One problem is the potential of sodium leaks leading to possible fires and explosions. Another is that the fuel rods need to be repositioned periodically without opening the reactor, so that the breeder-burner process continues for at least 50 years. Years of experience with liquid sodium provide reasonable confidence that the challenge of leaks can be met.
However, the use of supercomputers to model the proper placement of core fuel rods through use of remote instrumentation is a task without precedent. But given the fact that this incredible technology emerged from such science, technology and entrepreneurial stars as Teller, Wood and Gates, and with the China National Nuclear Corporation now joining the enterprise as a potential manufacturer, TerraPower is at the very least a credible endeavor.
To provide energy without generating greenhouse gases for the human race by 2050—including addressing a growing need for desalination plants, and aiding the production of hydrogen for fuel cells to replace gasoline powered vehicles—an estimate of 6,000 reactors for the world is reasonable. A ballpark cost is $1 billion each; that’s $6 trillion, or about one third of the current U.S. GDP. Given that most of the world’s countries would be contributing to this global initiative, however, it is possible that if TerraPower-type technology lives up to its promise, a world energy solution would not only be feasible—it would be affordable.
Source: Scientific American Blog Network
