The Literary Life of a Science Leader

Chapter 179 Almost Unsolvable High Energy Environment

Many people have played a game as a child.

During the Chinese New Year, firecrackers are lit, and then a pot is used to cover the firecrackers to see how the firecrackers explode.

Simply put, the fusion reactor is similar to this, and the first wall material is the basin.

There are two core issues with first wall materials, high-energy neutron irradiation and high-flux deuterium (D) tritium (T) plasma bombardment.

in high-energy neutron irradiation.

The current research is basically DT fusion, which is the easiest to achieve: each DT fusion produces a neutron of 14.1 MeV.Since neutrons are not charged, they cannot be confined by a magnetic field, and they will directly bombard the material of the first wall to cause damage.

Each DT fusion produces a 14.1 MeV neutron.Since neutrons are uncharged and cannot be restrained by a magnetic field, they will directly bombard the first wall material and cause damage.

14.1 MeV is a very large energy. It should be known that all kinds of chemical bonds bind the atoms in the material, and the bond energy is about 1-10eV.

In other words, the energy carried by a 14.1MeV neutron is enough to destroy millions of ordinary chemical bonds, which will undoubtedly cause irreparable damage to materials.

In the fusion reactor, high-energy neutrons are like bullets fired at the material, constantly hitting metal atoms, breaking the chemical bonds around them, forcing the atoms to leave their original positions, thereby destroying the entire atomic arrangement.

When the atoms are knocked away, a vacancy is naturally left in the original place, and such pits accumulate and accumulate inside the material, turning into large holes.

In addition, the atoms that are knocked away will not be small, but will diffuse to the surface of the material in various ways.Atoms are continuously transferred from the center to the surface, and the material slowly expands like a hollow foam. This size change is fatal to the material in normal service.

In addition to irradiation swelling, neutron irradiation produces a large number of defects in the material, which will also affect the mechanical properties of the material, making the material harder, more brittle, and more likely to break, thereby affecting the safe operation of the fusion reactor.

Neutrons will also undergo nuclear reactions with materials to change the elemental composition of materials. For example, metal W will become Re, Os, Hf, Ta.

Over time, the composition of the material will become completely different from the beginning, which will have a great impact on the material.

Although the problem of neutron irradiation also exists in fission reactors, the neutrons in fission reactors are much lower in energy and flux than fusion reactors, so the technology of fission reactor materials cannot be directly transplanted into fusion reactors.

In terms of high-throughput deuterium-tritium plasma bombardment.

The fusion reactor's confinement of DT plasma is not perfect, and a large number of DT ions in the reactor will bombard the first wall material.Because the price of T fuel is very expensive, hundreds of millions of yuan per kilogram, it is recycled in the fusion reactor through the reaction of neutrons and lithium.

In order to prevent T from staying in the material and not coming out, the first wall is made of tungsten, which has the weakest affinity for hydrogen among metals. After T enters the tungsten, it is difficult to effectively combine with the material itself, so it has to run out again and continue to participate in fusion.

Although tungsten itself does not combine with T, the cavity generated by neutron irradiation has a very strong attraction to T, once T runs into the hole, it is difficult to get out.

This causes the T fuel to remain inside the material, thereby destroying the T cycle above, making the T fuel less and less used.

Without T, fusion is naturally impossible.

In addition, as an isotope of gaseous hydrogen, DT forms gas molecules after entering the pores of the material.These gas molecules are squeezed into a limited space, which will form a very high pressure, which will squeeze out hydrogen bubbles, further cracking the material, and causing serious damage.

There is basically no DT problem in fission reactors. This problem is completely new for fusion reactor materials, and the research on this problem is still in the research stage.

Even the scientific phenomena of basic research have not yet been explained.

There is still a long way to go before the development of commercial fusion reactor materials. Don't ask, it will be 50 years after commercial use.

There are other difficulties as well.

The service environment in the fusion reactor is extremely harsh, which means that it is very difficult to do related experiments.

E.g.

Research on fusion reactor materials obviously requires neutron irradiation experiments, but neutron sources on this planet are very scarce, so doing a neutron irradiation experiment will not only cost a lot of money, but also take years to accumulate enough neutron sources. child damage.

There are only a handful of neutron irradiation data that can be found in the current literature, which is obviously detrimental to the development of new materials.

Nowadays, the study of fusion neutron irradiation often uses ion irradiation as an analogy, but it is still very expensive!
Moreover, the ions are also charged, and the penetration depth in the material is very shallow, and they are only concentrated in a few microns on the surface of the material; while neutrons can often penetrate the entire material, causing uniform radiation damage.

Therefore, it is hard to say how much of the results of ion irradiation can be used for neutron irradiation.

Another research idea is to use supercomputers to directly simulate the damage of neutron radiation to materials in the virtual world, but this is also what many research institutes are doing.

But this idea also faces great challenges.

To build a model in a computer, its time scale spans femtoseconds to years, and its spatial scale ranges from angstroms to centimeters. The difference of dozens of orders of magnitude in the middle is like a natural barrier.

No supercomputer can accurately simulate this process, and now we can only use various "spherical chickens in a vacuum" to simplify the model.

"What? Can you spare some time?" Professor Tian continued to encourage Mu Jingchi, "You can change your habit of getting home from get off work on time, and it's okay to go back two, three or four hours late."

Mu Jingchi shook his head, but still refused.

The material of the first wall is almost unsolvable for the current Mujingchi.

In this high-energy environment, any material structure will be broken. If the current homogeneous materials are not good, then there is basically nothing to do.Material science is all about trying to find a way on the microstructure of materials. The microstructure has been broken, and no matter how awesome the technology is, it won't work!
Even if Mu Jingchi gets the relevant knowledge about the future, there is no information about the commercial use of nuclear fusion.

Either there is no breakthrough in nuclear fusion in the future, or the knowledge extracted is limited and has not been included in the relevant knowledge of nuclear fusion.

From the current Mujingchi's point of view, this problem cannot be solved by simple materials.It requires the cooperation of materials, mathematics, physics, computers and other fields to complete.

Whether it is a tokamak, a star-like reactor, or a NIF with different principles, or a tri-alpha energy fusion reactor, it is impossible to bypass this first wall.

"You'd better find someone else!" Mu Jingchi shook his head, "I don't have the time and energy, nor the ability to do this first material research."

(End of this chapter)