China Claims Successful Fusion Power Test

SeaDour writes, "China claims to have carried out a successful test of its experimental thermonuclear fusion reactor. But what exactly made this test 'successful' is not clear. From the article: 'Xinhua cited the scientists as saying that deuterium and tritium atoms had been fused together at a temperature of 100 million degrees Celsius for nearly three seconds. The report did not specify whether the device... had succeeded at producing more energy than it consumed, the main obstacle to making fusion commercially viable.'" China is a participant in the 10-nation ITER project to build a fusion reactor in the south of France by 2015. The article quotes the research head of ITER as saying, "It was important for China to show that it is part of the club. Here are English language versions of the Chinese news release: announcement, background.

Comments

Re:Oh...

[RsG]

Nah, you want it to get as hot as possible. Higher temperature leads to more reactions in the fuel, which in turn leads to greater effeciency. Part of the problem is getting the fuel that hot in the first place, and keeping it together long enough to fuse.

Side note: while 100 million degrees sounds awfully hot, we're talking about a tiny amount of fuel here. The usual figure quoted for a hypothetical commercial reactor is about two grams of fuel in the core at any given time. The reactor itself doesn't get anywhere near that hot, even in the event of a full loss of containment.

Net gain not the obstacle!

[The_Wilschon]

Achieving a net energy gain is not the main obstacle to making fusion commercially viable. That has been done quite successfully. There is no problem passing break-even. It is ignition we are trying to achieve now. That is, a fusion reaction which produces enough heat to cause more fusion, provided enough fuel. If you're going to write an article about fusion, at least know something about the state of the field. Journalists should all be required to read the relevant wikipedia articles before publishing something about science.

Re:Net gain not the obstacle!

[The_Wilschon]

Go out and get yourself a copy of An Introduction to The Physics of Nuclei and Particles by Richard A. Dunlap, first edition, published in 2004. This is one of the standard texts for an undergraduate physics course in nuclear and particle physics. See pages 192 and 193, esp. Figures 13.12 and 13.13. Then read the text on page 192. I will reproduce it here for your benefit:

In Figure 13.12 the broken line represents unthermalized breakeven. This refers to the situation where the energy output of the reactor is equal to the energy input but the plasma conditions have been augmented by neutral beam injection. The solid line represents thermalized breakeven where the plasma conditions themselves are sufficient for net energy production. The shaded region represents ignition where the energy output is not only sufficient to yield a net energy gain but is also sufficient to maintain the plasma conditions. This is a self-sustained fusion reaction. These operating conditions refer to d-t fusion; conditions for d-d fusion would follow curves with values of n\tau about two orders of magnitude larger. The data points in the figure represent the operating conditions of a number of experimental magnetic confinement reactors. The general trend of the points from the lower left to the upper right of the figure represents the chronological development of fusion reactors from the late 1960s to the late 1990s. This line also represents an increase in reactor power from the mW range to several MW. Present results are in the breakeven region and future developments can hope to achieve ignition. The time scale for such developments is presumably in the order of several decades.

The figure shows 2 points inside the solid line, and 15 points between the solid line and the broken line. Figure 13.13 on the facing page is a similar plot, showing inertial confinement experiments rather than magnetic confinement. However, 13.13 lacks the lines showing the two breakeven points.

Allow me to repeat the particularly relevant phrases (emphasis mine):

The shaded region represents ignition where the energy output is not only sufficient to yield a net energy gain but is also sufficient to maintain plasma conditions. This is a self-sustained fusion reaction.

Present results are in the breakeven region and future developments can hope to achieve ignition.

Direct from a credible source. Now, perhaps Dunlap is wrong. Credible sources have been quite wrong in the past and will be in the future. However, you'd best have a stronger argument than "no you're a poopyhead" if you expect anyone to believe you.

Re:Containment?

[spike hay]

Magnetic containment. This isn't like fission reactions. There isn't a "pile." Just a couple of grams of non-radioactive deuterium and radioactive but fairly benign tritium. In the event that the magnets somehow fail, the reaction will stop, with just a bit of erosion on the sides of the reactor.

A Small Step

[quanminoan]

A fusion reactor has so many challenges behind it that ignition is only a small step towards something useful. Assuming you ignite a plasma you then have to maintain it, keep it stable, and fuel it fast enough to keep it burning. After that you're left with "mere" engineering problems, such as removing ~ 1 MW of heat per m^2 on the walls of the tokomak, making a gun fire a pellet of solid hydrogen into the plasma at one pellet per second, and finally creating a structure that can handle the intense neutron flux so the reactor can survive long enough to break even.

Though ITER is being built soon, it's being designed as its going up. I'm involved with creating an H- ion beam to inject the plasma (called neutral beam injection). The idea is to fire a high energy beam of neutral hydrogen into the plasma to heat it up (neutral so the atoms can travel through the containment magnets without deflection).

So even if the Chinese managed to build a reactor that beats previous records, it's a long while before fusion powers your home. Nevertheless I consider Fusion research to be one of the most important fields; it takes no imagination to understand what it would mean if nations could be powered on water.

Re:Here's an additional press release, more info

[dan828]

Well, the "Me so horny" prostitute was Vietnamese (from the movie Full Metal Jacket), and it's the Japanese that have problems pronouncing Ls, not the Chinese. So, besides mixing up three different asian countries with distinct languages and cultures, your ethnic insult was spot on. Way to go!