Feasible fusion power – the carrot before the donkey?
When I was about 10, I recall hearing that nuclear fusion power would become a reality “in about thirty years”. The estimate has increased steadily since then, and now, forty odd years on, we hear that fusion power will come on-stream “in about fifty years”. So, what is the real likelihood of fusion-based power stations coming to our aid in averting the imminent energy crisis? Getting two nuclei to fuse is not easy, since both carry a positive charge and hence their natural propensity is to repel one another. Therefore, a lot of energy is required to force them together so that they can fuse. To achieve this, suitable conditions of extremely high temperature, comparable to those found in stars, must be met. A specific temperature must be reached in order for particular nuclei to fuse with one another. This is termed the “critical ignition temperature”, and is around 400 million degrees centigrade for two deuterium nuclei to fuse, while a more modest 100 million degrees is sufficient for a deuterium nucleus to fuse with a tritium nucleus. For this reason, it is deuterium-tritium fusion that is most sought after, since it should be most easily achieved and sustained.
One disadvantage of tritium is that it is radioactive and decays with a half-life of about 12 years, and consequently, it exists naturally in only negligible amounts. However, tritium may be “bred” from lithium using neutrons produced in an initial deuterium-tritium fusion. Ideally, the process would become self-sustaining, with lithium fuel being burned via conversion to tritium, which then fuses with deuterium, releasing more neutrons. While not unlimited, there are sufficient known resources of lithium to fire a global fusion programme for about a thousand years, mindful that there are many other uses for lithium, ranging for various types of battery to medication for schizophrenics. The supply would be effectively limitless if lithium could be extracted from the oceans.
In a working scenario, some of the energy produced by fusion would be required to maintain the high temperature of the fuel such that the fusion process becomes continuous. At the temperature of around 100 – 300 million degrees, the deuterium/lithium/tritium mixture will exist in the form of a plasma, in which the nuclei are naked (having lost their initial atomic electron clouds) and are hence exposed to fuse with one another.
It is intersting to note that controlled fission was obtained (Chicago Pile 1, December 1942) before uncontrolled fission The Trinity explosion, July 1945). Nuclear power came into play about ten years later.
With fusion, uncontolled fusion took place in November of 1952, but controlled , and only is very small form, years later. We still do not have fusion power.
” the imminent energy crisis”
Huh?!? We’ve got 500 years of coal, (now) 200 years of shale gas (just with current tech), and 1000 years of nukes (using fast neutron and old school mix). And that’s just here in the US. The only energy crisis is the god-awful interference by politicians in the energy sector screwing up the whole parade.
Tritium is one of the most expensive materials on earth. It can only be made by nuclear reactions, an only one thermal neutron at a time. Lithium itself (the necessary starting material for tritium) is not cheap, and there are many competing demands for it, from batteries to medicines to high-tech coolant systems.
While lithium /tritiumreactions have been performedcommercially, the product usually decays significantly to heliu-3 before large amounts can be accumulated.
I thought of the competing industries wanting lithium, too. I think a large part of lithium goes to “earth-friendly” industries that would be ousted by fusion power. We cannot now make tritium with any efficiency. However, in researching and working with this problem, there may be a solution found, probably by chance. Just because we cannot now make something work at present……Anyway, that’s the argument for the those worthless turbines thrust upon society—they’re getting “better”. Fusion might actually produce reliable energy in the future. Let’s try something feasible for once.
Meanwhile, fission keeps working. Except in Japan.
Germany too.
A different approach to fusion; General Fusion’s approach does away with the huge containment and laser costs associated with enormous magnetic fusion and inertial confinement fusion machines, by building smaller fusion generators that use existing technologies, low-cost high-availability materials, and standard construction techniques.
Link: http://www.generalfusion.com
it’s still a research toy at this stage
I like the Thorium LFTR reactor for the next 50 years.
We also need fast neutron reactors as well. They will be fueled with all the left over rods from the old school reactors. It takes care of the “problem” with all the used rods as they can be reprocessed again and again until there is nothing left but low level radiation products.
The thorium units are great for small sealed units that can be placed in and around cities and small towns where power is needed close by due to distribution considerations. The Japanese have some really nice production units available right now.
There nice little nuclears in the USA too:
The Gen4 Module is a next generation design that uses a liquid metal cooled, uranium nitride fueled, fast-spectrum reactor that employs control rods for reactivity control. The reactor has been designed to deliver 70 MW of heat (25 MW of electricity) for a 10-year lifetime, without refueling.
http://www.gen4energy.com/