Energy breakthrough

Commercial nuclear fusion may still be decades away

A recent experiment at the National Ignition Facility (NIF) in the Lawrence Livermore National Laboratory in California indicates that nuclear fusion could be commercially viable, although it is still at least 15 to 20 years in the future. But together with encouraging results at the International Thermonuclear Experimental Reactor (ITER) in France (where India is also involved), this should lead to more investments, including private sector investments, in fusion research and development. Humanity has dreamt of clean, cheap, limitless energy since the 1950s, when scientists started working on fusion. But achieving commercial power means solving intractable problems at the cutting edge of physics and engineering. Fusion is clean. It has zero emissions, and doesn’t produce much radioactivity. The fuel — usually isotopes of hydrogen such as deuterium — is abundantly available, or relatively easily produced. Stars use fusion. Hydrogen (the lightest, most abundant element) is compressed under intense pressures and high temperatures and converted into helium with excess particles transformed into energy. As stars mature, other elements are also produced via fusion.

Simulating stellar conditions is hard. Complex, expensive machinery using massive power is needed to safely create conditions of intense pressure and temperatures of above 35 million degrees Celsius. Doing this and controlling fusion to produce stable power is even more difficult. Seven decades of research has made some of this possible. But in addition, commercial fusion means triggering reactions that generate more energy than required to create these stellar conditions. That was achieved for the first time at the NIF, though this result must be read with many caveats. There are three ways to trigger nuclear fusion. One is by setting off a fission explosion— an atom bomb. The explosion momentarily creates conditions that trigger a fusion explosion. This is how a “hydrogen bomb” works. It is obviously not a route to commercial power. One of the other two methods involves trapping hydrogen plasma (electrically charged gas) within a magnetic field to safely apply heat and pressure. This is being tried at the ITER and other facilities.

The NIF was looking at the third method, inertially confined fusion. This puts fusion material in a chamber made of a material that absorbs energy. The chamber is bombarded with high-energy lasers and it absorbs energy until destroyed in a fusion reaction. The calculations show that, in this iteration of an experiment, which has been done many times, the fusion released more energy than released from the lasers. This implies fusion can produce surplus power. The “chamber” was a tiny pellet made of gold, which could be held in the palm. The surplus energy produced was enough to light a 40 Watt bulb for a day or boil 15 tea kettles. Most crucially, the energy actually used to power the lasers was way more than the energy produced by fusion. Less than 3 per cent of the energy used to power the 192-laser-array was transmitted to the pellet.

Going commercial would involve big advances in laser efficiency, scaling up the gold pellet in size meaningfully, and making it out of cheaper material, doing this experimental process continuously to trigger fusion, and transmitting the surplus power generated. So, while this is an ingenious experiment and it offers assurances fusion is viable, commercial usage still looks to be in the distant future. But the good results out of NIF and the encouraging work at ITER will surely spark more research. That could lead to more breakthroughs.