fredag 12. april 2013

The Roadmap for nuclear fusion: Delayed by funding issues

av Ralph Kube, Stipendiat ved Institutt for fysikk og teknologi, Universitet i Tromsø

Research in fusion energy began in the 1950s when researchers realized the huge energy potential that was possible to harness from this energy source. At the time, tapping the strong nuclear force as energy source was only possible through nuclear fission, which is by splitting unstable heavy nuclei and utilizing the residual heat.

On the one hand, fission plants deliver steadily large amounts of electricity. On the other hand, this same power source has been responsible for large catastrophes, where their far-reaching consequences still difficult to grasp.

So why not harvesting energy through fusion instead, it is safer. Reaction yields for fusion processes are in the same order of magnitude as for fission processes and around 3 orders of magnitude larger than for chemical reactions.

The original idea for a fusion reactor is, as phrased by the French Nobel laureate Pierre-Gilles de Gennes,  "We say that we will put the sun into a box. The idea is pretty. The problem is, we don't know how to make the box." This has been the major research focus in nuclear fusion for the past 40 years, in a nutshell.

To sustain a fusion reaction, one has to heat up gas to some 150.000.000 kelvin so that the gas turns into plasma,
and confine the plasma by magnetic fields while avoiding contact between the plasma and the reactor walls. In this environment, light nuclei fuse to heavier ones, producing fast neutrons and alpha particles. The kinetic energy from the neutrons is harvested in a heat exchanger surrounding the fusion chamber.

Such requirements push the boundaries of physics, engineering and material sciences. In the 1950's energy from nuclear fusion was only fifty years away. Now, sixty years later since the first prediction, current roadmaps predict that the first functional reactor, designed to yield several Giga-watt of power, would be put out on grid by 2040. 

What has gone wrong?

The biggest problem with international fusion programs is funding. Once, several alternatives with different levels of funding requirement were suggested by the US Department of energy’s road map toward accomplishing fusion energy. Among the alternatives, the most ambitious but expensive one would have lead to a functional reactor by 1990. A moderate and reasonably less costly alternative of those, would have given us a reactor in 2005. However, the actual annual budget allocated to research turned out to be much less than the amount envisioned when the road map was published.

Even with the scarce resources; however, impressive results were possible to achieve in the field. The last few decades’ advancement in the areas of plasma confinement, reactor operation and material sciences have cleared the way for the ITER test reactor, which its construction has recently begun in southern France. ITER, previously meaning "International Thermonuclear Reactor", now "ITER" to mean " the way in Latin", is expected to demonstrate the realization of fusion energy. There is a huge scientific ambition behind the ITER project: to be able to confine a burning plasma for several minutes yielding 500MW, i.e. 10 times the power needed for running the reactor. This is extremely larger when compared to what has been possible to achieve by the current world record holder in fusion energy, JET, a facility in England that has reached a peak yield of 16MW for less than a second.

The first plasma discharges test in ITER is planned for 2020. In 2027, the first fusion experiments will be running in ITER. Outcomes from the ITER project, in addition to being of great value to the scientific community, could contribute to bring nuclear fusion on the list as safe, environmentally friendly and reliable power source.

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