What is the reason why the 'breakthrough' of nuclear fusion has not yet led to the realization of practical fusion power generation?

Nuclear fusion, which holds great promise as the energy of the future, is said to be much safer than nuclear fission, which has a high risk of going out of control due to a chain reaction. The news site

IEEE Spectrum says, 'It's just a small step on the long road to commercialization of fusion power generation.'

Fusion “Breakthrough” Won't Lead to Practical Fusion Energy - IEEE Spectrum

On December 13, 2022, the United States Department of Energy announced that the laser fusion experiment conducted at Lawrence Livermore National Laboratory succeeded in `` fusion ignition '' that can output higher energy than the input. And the National Nuclear Security Administration (NNSA) has announced that the successful experiment is a 'breakthrough' in nuclear fusion.

Announced that the Ministry of Energy has officially confirmed 'ignition' by achieving output exceeding energy input in nuclear fusion experiment - GIGAZINE

At Lawrence Livermore National Laboratory, we are conducting experiments on `` inertial confinement laser fusion'' that causes a nuclear fusion reaction by irradiating a small capsule containing hydrogen plasma with a laser.

Regarding the success of this fusion experiment, IEEE Spectrum said, 'It's just a small step toward the commercialization of fusion power generation,' and points out the problems with fusion power generation.

The first problem is that the laser required for nuclear fusion power generation is required to be 100 times more efficient than the laser used in this experiment. In an experiment at Lawrence Livermore National Laboratory, the energy generated by the hydrogen capsule was 3.15 megajoules , and the energy of the injected laser was 2.05 megajoules. However, 'laser energy' and 'energy required to irradiate the laser' are completely different things. Since the laser irradiation performed in the experiment requires about 300 megajoules per time, it is still far from realization to generate energy that exceeds the `` energy required to irradiate the laser '' by nuclear fusion reaction. That's what IEEE Spectrum points out.

The second problem is the low frequency of laser irradiation. Lawrence Livermore National Laboratory in 2022 irradiates the hydrogen capsule with a laser several times a year, but IEEE Spectrum says, ``When performing nuclear fusion power generation, the laser is irradiated several times per second. is ideal,' he points out that the current laser irradiation frequency is still insufficient for ideal nuclear fusion power generation.

A third problem is the need to convert the generated energy into usable power. In nuclear fusion power generation, the fusion reactor is wrapped in a box called a blanket , and the heat generated by absorbing neutrons is used to drive a steam turbine. Stephen Cowley, Director of the Princeton Plasma Physics Laboratory ``We have created a mock-up blanket, but we have never created a practical blanket,'' he said. IEEE Spectrum points out that it has not been developed.

The fourth problem is the high cost of operating and maintaining fusion reactors. It costs hundreds of thousands of dollars (tens of millions of yen) to manufacture one hydrogen capsule used at Lawrence Livermore National Laboratory. In addition, the output of the laser at Lawrence Livermore National Laboratory is very powerful, damaging the equipment in the facility each time it is irradiated, and the cost required for current fusion experiments can be enormous. Pointed out by IEEE Spectrum.

As a fifth problem, it is not clear whether fusion power generation, which is in the early stages of development, can be commercially competitive, and the current situation is that no consideration has been given to the feasibility of commercialization. . In other words, it is pointed out that even if the fusion experiment is successful at present, it is unclear whether it can be developed into a commercial fusion power generation.

On the other hand, IEEE Spectrum says, 'Nuclear fusion power generation is not hopeless,' and that the energy output can be rapidly improved by simply increasing the laser output.

Mr. Cowley said, ``Until now, the idea was that nuclear fusion power generation using the magnetic confinement method was possible, but according to the results of experiments conducted by Lawrence Livermore National Laboratory, fusion power generation using the inertial confinement method is considered to be a possibility for fusion power generation. It showed the possibility of being a road to realization, ”he acknowledges that there is still room for research on how to convert the energy generated by nuclear fusion into electricity.

in Science, Posted by log1r_ut