500MW from half a gram of hydrogen: The hunt for fusion power heats up
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You’ve heard of the Manhattan Project — the Allied research and development program that resulted in two nuclear bombs being dropped on Japan and the end of World War II — and now it’s time to learn about one of its successors, Project Matterhorn, a Cold War program to control and harness thermonuclear reactions to create fusion power.
Nuclear fusion occurs when two atoms fuse together (usually hydrogen) to form a heavier atom (helium), and releasing a vast amount of energy in the process. This process can only occur at incredibly high temperatures, such as the center of a star (such as our Sun). Every second, the Sun fuses 500 million tons of hydrogen into helium, releasing about 5 million tons of gamma rays that eventually heat and illuminate Earth. For a long time (Project Matterhorn started in 1951), nuclear fusion has been considered a very desirable power source because the fuel is virtually free, and the process releases vast amounts of energy and no pollutants.
There are two competing approaches for the artificial creation of nuclear fusion: Magnetic confinement, which uses massive magnetic force to contain the fusing plasma within a tokamak (doughnut) device, and inertial confinement, which uses lasers to create enough heat and pressure to trigger nuclear fusion. Magnetic confinement is usually considered a better prospect for the limitless production of clean energy — and indeed, magnetic confinement will be used by the 500-megawatt ITER fusion reactor in France — but a lot of work is still being done on inertial confinement by the likes of California’s National Ignition Facility (NIF), which uses 500 trillion watts of laser light to kick-start fusion reactions.
So far the main problem with fusion power generation is that it doesn’t actually produce more thermal energy than the electrical energy required to keep the reaction going. In its current form, fusion power is useless. Hopefully, though, a new discovery made by Princeton Plasma Physics Lab (PPPL) — the home of Project Matterhorn in the ’50s and ’60s — could result in magnetic confinement fusion that breaks even, or even produces electricity.
Basically, to keep fusion going you need to sustain a temperature of around 11 million degrees Celsius, which requires a huge amount of electricity. Fusion chambers are usually lined with heat-resistant carbon tiles in an attempt to reduce wastage, but the problem is that protons and neutrons escaping from the fusion reaction hit the wall, cool down, and then bounce back into the reaction, reducing the temperature. Electricity must then be used to increase the temperature back to 11 million Celsius.
The PPPL, led by Bruce Koel, have found that a thin layer of lithium metal (the third element in the Periodic Table) absorbs these protons and neutrons, preventing them from bouncing back into the pot, and thus reducing the power requirement of keeping the fusion reaction going. The research is still in its early stages — Koel and co are now analyzing whether lithium is viable over the long term — but so far, PPPL seems fairly confident that lithium will enable the construction of smaller, more efficient fusion reactors.
Meanwhile, at ITER, a vast fusion chamber that’s three stories high is due to begin fusing deuterium-tritium fuel in 2026. ITER is hoping to produce 500 megawatts over 1,000 seconds from just 50 megawatts of input power and 0.5 grams of hydrogen fuel. If it’s a success, an actual fusion power plant, called DEMO, will be built. NIF, the 500-trillion-watt “star power” laser fusion center, hopes that 2012 will see the first experiment that produces more power than it consumes — and pending successful ignition, the Lawrence Livermore National Laboratory will begin full scale planning on the LIFE power plant.
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