In my last post, I talked about the International Thermonuclear Experimental Reactor ITER project. A consortium of nations including European Union, India, Japan, People's Republic of China, Russia, South Korea and the United States formally agreed in 2006 to collaborate on the construction of an experimental nuclear fusion reactor. Billions of dollars and decades of work are dedicated to the project. Today I am going to delve into some of the technical details of the ITER reactor.
ITER will utilize the fusion of deuterium and tritium to create helium and release energy. This is the equation for the ITER fusion reaction:
The top number for each element is the number of neutrons and the bottom number is the number of protons. The product of fusion is a helium nucleus, a neutron and over seventeen million electron volts of energy. This reaction requires the least energy to ignite of all the possible fusion reactions. It produces about three times the amount of energy released by uranium fission and millions of times more energy than any chemical reaction such as burning coal can release. Tritium today is created in nuclear reactors but there is a virtually an infinite supply of deuterium and tritium in the oceans of the world. There is also a lot of tritium in the soil on the Moon that could possibly be mined.
ITER is based on the tokomak design. This is a donut shaped chamber surround by powerful magnets. The plasma of deuterium/tritium injected into the change then heated and confined by magnetic fields. Beyond the wall of the chamber, there are test blanket modules that include one that will absorb the neutrons released by the fusion and breed more tritium from lithium in the blanket. When completed, ITER will weigh about five thousand tons. It will be the biggest tokomak ever constructed at sixty four feet in diameter by thirty seven feet in diameter.
The ITER is supposed to be able to generate about five hundred megawatts for a period of at least one thousand seconds. In order to accomplish this, about two hundredth of an ounce of a deuterium/tritium mixture will be fused inside the approximately one thousand cubic yard reactor chamber. It is hoped that ITER will be able produce ten times the amount of energy that is consumed to heat the plasma although no attempt to convert heat to electricity will occur. The following is a list of goals for the ITER project:
- To momentarily produce ten times more thermal energy from fusion heating than is supplied by auxiliary heating (a Q value equals 10).
- To produce a steady-state plasma with a Q value greater than 5.
- To maintain a fusion pulse for up to 480 seconds.
- To ignite a 'burning' (self-sustaining) plasma.
- To develop technologies and processes needed for a fusion power plant — including superconducting magnets and remote handling (maintenance by robot).
- To verify tritium breeding concepts.
- To refine neutron shield/heat conversion technology (most of the energy in the D+T fusion reaction is released in the form of fast neutrons).
As I said yesterday, there have been many problems, delays, cost increases, design changes, etc. that may ultimately overwhelm the project. It is quite possible that ITER will never be completed and operated as envisioned.
Artist's cutaway diagram for ITER:
