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Unlimited fuel, unlimited power, no waste, safe, no CO2.
There is the long term hope and possibility that the FUSION process can provide a future source of unlimited electrical power and it has the following advantages over other forms of power generation:-
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There is unlimited fuel available.
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The process does not produce CO2 or other greenhouse gases..
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It is inherently safe. If anything goes wrong it just shuts down.
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There is no medium term shutdown heat (unlike fission reactors.)
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There are no byproducts that could be adapted for military purposes or used by terrorists
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There are negligible waste products (ref 149.)
However this solution will not come in time to limit carbon emissions to the amounts required in the next 40 years. The process needs considerable power to start up therefore other green methods of electrical power production will always be needed and are likely to be well developed by that time.
Light atoms are fused to produce energy (heat).
In the Fusion process 'light' atoms are fused together to release heat. This is the same process as in the sun and the source of all our energy on earth. Deuterium and Tritium, the best of 13 possible fusion fuel combinations, are fused to create Helium 4 plus neutrons and energy (heat.)
Tritium (half life 12.5 years) is bred from lithium in the torus (red is positive):-
More details of the Fusion Process
There are two approaches to achieving commercial fusion:-.
1)Tokomac (Torus). JET and ITER - Plans for further research and development.
An initial experiment in the UK is the JET (Joint European Torus) fusion experiment (ref 107) which has resulted in an output of 16 MW for 1 to 2 seconds from an input power of 24MW. The whole site consumed 100 MW however. There are other experimental tokomacs in Russia, USA, Japan, less advanced.
The larger International Thermonuclear Experimental Reactor (ITER)(ref 149) is to be built in France with participation of the EU, Japan, China, Russia, US, South Korea. This experiment aims to generate 500 MW from an input of 50MW (ref 121). The site however will consume 200MW. The first "burn" is expected around 2022.
After this, several experimental reactors around the world would be planned, which should each generate 1300 MW with a net output this time at 1000 MW each.
V strong magnetic forces, v high temperatures, vacuum enclosure, near zero absolute temperature for superconductivity, in a torus.
At 100 million degrees the gas (fuel) exists as plasma where the electrons (-) and ions (+) are separate.
The Tocomac fusion process relies on magnetic forces to confine and isolate the hot plasma fuel in a vacuum (as no material would remain solid at the temperature of 100 Million deg. C) in a large Torus. Pulsed electrical current around 8 minutes (ITER) and up to 7 million amps is induced in the plasma by transformer action, using superconducting coils.
The magnetic forces are created by a toroidal field, produced by coils (18 for ITER), surrounding the vacuum vessel and a field produced by current in the plasma. These form a helical field around the torus to confine the plasma. Other coils shape and position the plasma.
Heating the plasma is carried out by several methods, the induced current in it, beams of deuterium and tritium ions injected into the plasma (first neutralised), radio frequency energy and microwave energy, the helium nuclei (alpha particles) produced - the latter which keeps the reaction going.
The energy is transferred via alpha particles and neutrons and heat will be extracted from heat exchangers within the lithium blanket, steam generated and used to power turbo generators.
No impurities must be present so a very low vacuum is required within a vacuum vessel (see sketch below)
A lithium blanket is placed in the vessel to make ('breed') tritium (half life of 12.5 years) (see sketch).
The main cryogenic load is liquid helium cooling of the magnets to achieve superconductivity at 4 deg K (absolute.) The cross section of the ITER torus has been changed from the more circular JET shape to D shape.
"Ash" in the form mainly of Helium is extracted and reprocessed. The ports for introducing Deuterium and Lithium are not shown in the sketch.
2) HIPER -alternative approach using huge lasers might bring fusion power earlier.
An experiment at the Rutherford Appleton Laboratory in Oxfordshire has led to a decision to build a prototype experimental reactor or Hiper (high petawatt energy reactor.)
A fuel pellet of Deuterium/Tritium of the order of 2 mm wide is be fired across a steel vacuum chamber. Pulsed lasers using 1 petawatt of power would be directed to hit the pellet fast enough to very quickly compress it, reduce it to a size of a few microns and to a temperature where fusion can take place. This could optimistically lead to fusion power by the middle of this century (refs 159.)
The National Ignition Facility (US) is building a multi laser device of very high energy to bombard hydrogen and create fusion.
more detail of multi laser device See National Ignition Facility.
Fuel options plentiful.
100 kg of Deuterium (obtained from 2800 tons of sea water) and 150 kg of tritium (obtained from 10 tons of lithium ore) could in the future produce 1000 MW of electrical power for 1 year (ref 138). There is sufficient Lithium to provide all the worlds energy for 1000 years and of course unlimited water. Tritium can also be produced in a heavy water moderated reactor.
A Deuterium - Deuterium fusion reactor/device would provide limitless energy from only water. However even higher temperatures would be required so it is unlikely to be considered in the near future.
40 years before fusion likely to make an impact
It will probably take ten years before the ITER experiment is operational, ten years before problems are ironed out, another ten years to build several demonstration reactors around the world and another ten before these are proved (ref 149).
Considerable development must follow and new materials found. The digital mock up of JET has a million parts and of ITER 10 million parts to design and construct (ref 157).
Sketch of JET interior:-
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