Friday, May 24, 2019

The Nuclear Fusion Delusion (Part Two)

May 21, 2019 Posted by

In this article we will detail the other extensive problems that nuclear fusion faces that were not covered last week in part one of our piece. There we focused on the difficulties of scaling down the chemistry and physics of our Sun to an operation on Earth.
We can obtain energy by fusing two deuterium nuclei found in low concentrations in sea water (deuterium is an isotope of hydrogen containing one proton and one neutron, in contrast to normal hydrogen which has no neutrons). However, their reactivity is 20 times less than if you fuse one deuterium nuclei with one tritium (which has one proton and two neutrons). Tritium, however, is not normally found in nature. This is because it has a half-life of only 12.3 years. Once created naturally in nature, it is relatively quickly gone. Nature is thus not a reliable source of what we need for efficient potential production of fusion energy. Therefore, we must create a reliable supply of tritium which can only be practically achieved in our old reliable fission reactors. Of course, a primary reason for the support of fusion is to get rid of fission reactors for their perceived safety problems. We say ‘perceived’ as we can now build fission rectors, far advanced from those of the past, which are inherently safe. But that is a story for another day.
Another wonderful advantage of using deuterium/tritium is that the temperature required is well below the 100 degrees Celsius needed for deuterium/deuterium fusion under the conditions we can currently create on Earth. Therefore, most of the ongoing research will be using the tritium isotope. Fortunately, there is a way once we have the tritium generated from a fission reactor to conserve it in a fusion reactor. It is a bit like having your cake and eating it too. Bear with us, we are talking nuclear physics after all and you never expected it to be child’s play.
The tritium component of the fusion fuel can be generated or at least saved in the fusion reactor itself as so little is actually consumed in the nuclear reaction. To quote Dr. Daniel Jassby, the former nuclear physicist at the Princeton Plasma Physics Lab that we cited in part one of this article,
“a lithium containing blanket must be placed around the reacting medium—an extremely hot, fully ionized gas called plasma. The neutrons produced by the fusion reaction will irradiate the lithium, breeding tritium.”
Think of it a bit like adding red paint to blue paint and getting brown paint. It is a little more complicated than that but it works, but not perfectly—at great expense, we will still need to keep fission reactors operating to make up for the shortfall of tritium. That huge cost could drive us back to deuterium/deuterium reactors with their many deficiencies mentioned in part one of this series.
A more significant and totally unresolvable problem with fusion reactors is the energy they require to operate, called parasitic power consumption, which will likely always be greater than the power they develop through the release of energy from fusion. There are two types of parasitic power requirements. The first is the energy required to run auxiliary systems such as liquid helium refrigerators, water pumping, heating, ventilating, and air conditioning. When fusion operation is interrupted for any reason these systems must keep running and all the power to operate auxiliary systems must be purchased.
The second category of parasitic power requirements is that required to control the fusion plasma in magnetic confinement systems. It requires injection of electromagnetic energy to stabilize the fusion burn. After each fusion pulse, if they occur, electric current must charge energy storage systems such as huge capacitor banks. However a system is scaled, the power required to run the magnetic confinement systems will consume a very significant portion of the power it is hoped to generate. Jassby tells us:
“to have any chance of economic operation that must repay capital and operational costs, the fusion power must be raised to thousands of megawatts so that total parasitic power drain is relatively small.”
Those who promote fusion almost like a religion often boost another dogmatic crusade—the misguided belief humanity’s carbon dioxide emissions are in any way dangerous.
For example, the web site of the France-based multi-nation ITER project asserts:
“Fusion doesn’t emit harmful toxins like carbon dioxide…”
Of course, carbon dioxide is anything but toxic. It really is an invisible gas essential to plant photosynthesis, and so to all life. And, the impact of anthropogenic carbon dioxide on climate is almost certainly very small.
Fusion zealots have also closed their eyes to the problems fusion reactors have in common with fission reactors. Neutron radiation in the reactor can ultimately destroy the containment structure. There is also radioactive waste that needs to be disposed of. There is always a potential for a radioactive tritium release. Also, coolant requirements are huge, as are operating costs. And despite the assurances of fusion activists, there remains some potential for nuclear weapons proliferation.
However, since no one has yet been able to create a seriously measurable amount of energy from nuclear fusion on Earth, associated problems can be ignored until some degree of success is achieved. Thus, nuclear fusion will remain 50 years away for the foreseeable future. It’s time to divert the research funding to more promising ventures. Image: Source:

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