Much has been made about the National Ignition Facility – a US Government facility where as massive array of pulsed power lasers is used to irradiate a tiny capsule of deuterium and tritium in order to produce nuclear fusion. NIF is a truly giant scientific installation, and there’s no disputing its one of the foremost “big science” centers in the world for things like laser optics, pulsed power, plasma physics and nuclear fusion. The technology is impressive and it will surely produce volumes of important scientific data.
However, there is some confusion, much of it intentional, about the purpose and capabilities of the facility.
It is often portrayed as an experimental prototype for a power-generating fusion reactor. It’s really not. The design of the facility precludes it from ever producing useful energy and that’s not the point. It’s also not the primary objective of NIF to research how nuclear fusion can be harnessed to produce usable energy. Data to that end may be generated in the process, but the basic design of the facility precludes such a system from being turned into a power plant.
The stated goal of the facility is also often reported inaccurately. Achieving “ignition” simply means that enough fusion has occurred for additional fusion to be produced without more external power. In other words, the reaction becomes self-sustaining, if only for a tiny fraction of a second. Ignition has not yet been achieved, though it is hoped it soon will. However, it’s less dramatic than it is often described. The moment when the calculations come back and reveal that the point of ignition has been achieved will not really be that revolutionary. it won’t mean that suddenly boundless energy is being produced. After all, nobody doubts that ignition is possible, it is only a question of how much power will need to be concentrated before it actually happens.
Via the Guardian:
Sustainable nuclear fusion breakthrough raises hopes for ultimate green energy
Scientists have moved a step closer to achieving sustainable nuclear fusion and almost limitless clean energy
US researchers have achieved a world first in an ambitious experiment that aims to recreate the conditions at the heart of the sun and pave the way for nuclear fusion reactors.
The scientists generated more energy from fusion reactions than they put into the nuclear fuel, in a small but crucial step along the road to harnessing fusion power. The ultimate goal – to produce more energy than the whole experiment consumes – remains a long way off, but the feat has nonetheless raised hopes that after decades of setbacks, firm progress is finally being made.
Fusion energy has the potential to become a radical alternative power source, with zero carbon emissions during operation and minimal waste, but the technical difficulties in demonstrating fusion in the lab have so far proved overwhelming. While existing nuclear reactors generate energy by splitting atoms into lighter particles, fusion reactors combine light atomic nuclei into heavier particles.
In their experiments, researchers at the National Ignition Facility at the Lawrence Livermore National Laboratory in California use a bank of 192 powerful lasers to crush a minuscule amount of fuel so hard and fast that it becomes hotter than the sun.
The process is not straightforward. The lasers are fired into a gold capsule that holds a 2mm-wide spherical pellet. The fuel is coated on the inside of this plastic pellet in a layer as thin as a human hair.
When the laser light enters the gold capsule, it makes the walls of the gold container emit x-rays, which heat the pellet and make it implode with extraordinary ferocity. The fuel, a mixture of hydrogen isotopes called tritium and deuterium, partially fuses under the intense conditions.
No, they didn’t actually get more energy out of the system than was put in. They just got slightly more energy from the reaction than the amount of energy deposited on the fusion fuel capsule to make it happen. It’s really not getting us any closer to using nuclear fusion as a limitless energy source. In fact, it should be noted that this is far from the first time humanity managed to get a lot more energy out of a fusion reaction than was used to initiate it. That happened in 1952 and was significantly larger.
A few facts to put it in context:
Posted in Good Science, Misc, Nuclear, Politics