Today's physics colloquium at Harvard was about the fusion. Robert Goldston from Princeton did a very good job. The previous article about ITER and fusion on this blog was posted here, and many well-informed people added interesting comments for which I am grateful.
Goldston discussed a lot of physics issues connected with the stabilization of the plasma; magnetohydronamics (MHD); heat diffusion, and so on. The inflow of professional information was pretty fast. He described an equation due to David Bohm, and he distinguished the Bohm regime of the plasma from the gyro-Bohm regime. The Bohm regime is hopeless - the diffusion is far too strong. The gyro-Bohm regime is what will allow the fusion plants to operate, and they can show that this regime can be realized.
Nevertheless, the talk looks like good news. The understanding of the relevant plasma physics has improved significantly in the last few years or decades - for example since the moment when Jimmy Carter started to fund this research by big money. The energy that the people are able to create by fusion has jumped by 14 orders of magnitude - well above the 6 orders of magnitude how much the computers became stronger in the same period of time. The power generated using the current devices is roughly 1 or 2 orders of magnitudes away from the goal - from profitable power plants. Well, one must also be able to stabilize the plasma for slightly longer time intervals than what can be done today, but it seems that they're getting pretty close in this respect, too.
A minor problem is that we still don't have a functional reactor. But don't be too impatient.
The relevant technology that the experts are developing is based on following principles:
- Deuterium plus tritium (their cost is virtually zero) burns to an alpha particle plus a fast neutron
- The plasma is usually confined into various toroidal shapes and stabilized by strong magnetic fields - the required large magnets are the most expensive part of the device
- There can be interesting "twisted" tori that are more appropriate to keep the plasma stable
- The fast neutrons are absorbed by a wall that can be as thick as 70 centimeters
- Every three years or so, the first 20 centimeters become radioactive and the material is not solid enough, and therefore this layer must be replaced
- The remaining 50 centimeters may be used permanently
- The power plant would be safe because there is never too much material in the system that could cause an explosion - like in the fission reactors where the Chernobyl's simpleton who was testing it could have caused the third biggest nuclear disaster in the history of humankind after Hiroshima and Nagasaki
- The reactors would generate radioactive waste that however disintegrates quickly - in 80 years it is mostly gone
It seems pretty self-evident that the future of fusion reactors is shifting from pure fundamental physics to engineering and economy - at the general level, the principle has been validated. In order to create an efficient power plant, one of them should cost less than 3 billion dollars, to say a rough number.
ITER, a next important step in the development of usable fusion reactors, will be located either in France, or in Japan. The country who wins the contract will enjoy various technological and economic advantages. Consequently, the Japanese say that the Europeans are assholes, while the Europeans describe the Japanese as jerks. It's obviously a lot of fun.
The U.S. are out of this particular game because a new source of energy would not be as hot as in these other, overpopulated industrial countries. I am sure that most readers will only be interested in the ways how to politicize this scientific and technological question. So let me emphasize that the United States and the Soviet Union started with ITER in 1985, and the U.S. still play an essential role in the research of various approaches to the fusion.
The budget to develop a working version of the reactor is estimated to be roughly 60 billion dollars - it's like a monthly U.S. trade gap. (Well, the Canadian statisticians forgot some files in their counting of November imports, which implies that the November U.S. trade gap was actually below 60 billion dollars.)
Sixty billion dollars - is it a lot of money? Goldston has shown some numbers. By 2100 or so, the world will require a lot of energy - roughly 3 times more than today - and it will want to choose the sources that don't produce much carbon dioxide. Replacing the CO2 emitting plants by the established alternative sources would cost roughly 300 trillion dollars. Do you see the factor of 5,000? The naive application of the Kyoto-like protocols using the available technology is therefore approximately 5,000 times more stupid a way to solve any hypothetical problems related to CO2 than funding the fusion research. Imagine that you remove 99.98% of someone's brain - is not it enough to identify the straightforward Kyoto supporters as anti-scientific morons?
The development of a working reactor is not on the schedule, but it is on the budget. Many countries, such as South Korea, are taking this project seriously and pay enough money so that the progress can be made.
