Chapter 523 Don't Take the Usual Path

With the sketch, Chief Engineer Wang left the STAR Stellarator Research Institute, and returned to the headquarters of the Nuclear Industry Group in Shanghai on the same day, and contacted the experts in the field of magnetic fluid power generation in the Engineering Academy, and discussed the possible application of magnetic fluid power generation technology. The feasibility of application on controlled fusion devices was discussed.

However, although the leader of the team left, the working group of the nuclear industry group still stayed in Jinling, and continued to communicate with the researchers of the STAR Stellarator Research Institute on technical issues.

At the same time, the experiments on the STAR device did not stop there.

After securing sufficient funding, the institute was so extravagant that it carried out an experiment every three days, using hydrogen and helium as the research objects to observe various complex physical properties of the plasma in the stellarator.

Even, in order to collect valuable data, Lu Zhou even ordered to inject 1mg of a precious deuterium/tritium mixture into the reaction chamber, risking damage to the material of the first wall to carry out a trial ignition.

In fact, this experiment did cause some damage to the STAR device, but fortunately the damage is still within the repairable range. But even so, the entire device must not be shut down for maintenance for a month.

Of course, although the cost is high, the rewards are also quite generous.

They not only verified the feasibility of this technical idea to achieve fusion reaction ignition, but also obtained a lithium sheet bombarded by a neutron beam carrying 14 MeV energy.

Especially for the latter, its scientific research value cannot be converted into money.

In China, they are probably the only ones who can do such a luxurious experiment.

At this very moment, this hard-won lithium metal sheet is quietly lying on a specially treated oxygen-free glass slide, and is observed under a scanning electron microscope by staff wearing protective clothing.

In the laboratory outside the isolation room, Lu Zhou and other researchers standing in front of the computer saw the data and pictures collected from the scanning electron microscope on the screen.

As they expected, the metal surface that was originally regular is now riddled with holes.

Through the detection of infrared spectrometer, traces of helium and tritium elements can even be observed in the tortuous channels.

What is gratifying is that this shows that the neutron beam carrying 14MeV energy did react with 63Li, and they successfully recovered part of the tritium element in the experiment.

As for the frustrating thing...

They faced too many problems, and they couldn't finish it in a few words.

Looking at the image on the computer screen, Professor Li Changxia sighed lightly.

"I bet this thing would shatter if touched lightly."

"Don't bet, even if you haven't been bombarded by a neutron beam, this thing can't be said to be very strong." Lu Zhou said casually, staring at the hard-won data on the computer screen.

Sheng Xianfu shook his head: "It's not just the problem of radiation damage, the multiplication ratio of tritium production is too low. And the most critical problem is not the recovery itself. The energy carried by the neutron beam is too high, and it is often not compatible with the surface. The 63Li reacts, but scurry inside the cladding material, even if the tritium we need is produced, it is left inside the material and cannot be released at all.”

The neutron carrying 14 Mev energy is like a cannonball, and all metal bonds are as vulnerable as toys in front of it.

Moreover, the neutrons penetrating the first wall are not just as simple as punching a hole in the first wall, they will form a cavity inside the first wall material like blowing a balloon, and finally lead to the overall loss of the first wall material. Swelling, embrittlement, and even detachment of surface materials can cause serious accidents.

And this is also one of the main reasons why fission reactor cladding materials cannot be directly used in fusion reactors.

The difference between the two materials in terms of radiation damage resistance is two orders of magnitude.

So far, their research has entered uncharted territory, which means that there is no previous experience to refer to. What to do next and how to solve these problems all depend on their own thinking.

After thinking for a while, Professor Li Changxia tried to suggest: "How about using molybdenum as the structural material?"

"Molybdenum is not good," Lu Zhou rejected the proposal for a moment, shaking his head and said, "Molybdenum has good heat resistance, but it will be transmuted into radioactive elements under neutron irradiation."

Another researcher continued to suggest: "What about tungsten? Tungsten has good heat resistance, and the transmutation products are osmium and rhenium, so there is no radioactive problem!"

This time there is no need for Lu Zhou to speak, Professor Li Changxia shook his head, "It's an old-fashioned question. The heat resistance of tungsten is fine, but the plasticity is too poor. Thermal stress will cause the surface of the material to crack... I did it in the DIII-D experiment. When I visited the laboratory, there was a special report on this issue, which was devoted to discussing this issue. In short, it is impossible to use tungsten.”

The laboratory fell into silence again.

At this moment, Lu Zhou, who had been staring intently at the data on the screen, suddenly spoke.

"If we can't keep the neutron beams in, why don't we consider putting them through?"

"Let it pass?" Sheng Xianfu was slightly stunned, then shook his head with a smile, "How can we recover the neutrons produced by the reaction?"

The recovery of neutrons produced in the DT fusion reaction is a key part of the entire nuclear fusion reactor technology. After all, the price of tritium resources is tens of thousands of times higher than that of deuterium. Not only is it sold in terms of grams, but the cost of one gram is as high as 30,000 US dollars (17 year data).

If the neutrons generated by the reaction cannot be recovered, not only will a large amount of energy be lost, but also the reactor will be "shutdown" due to the loss of tritium.

In an ideal fusion reactor, both tritium and neutrons should be preserved as intermediate products, and the final waste is only helium and heat.

Therefore, it is impossible to let go of the neutron, and you have to keep it no matter what.

Hearing Sheng Xianfu's rhetorical question, Lu Zhou smiled lightly and continued.

"Leaving them alone does not mean letting them go. In theory, no matter how we design the structure of the first wall, we cannot avoid the damage of neutron beams to the metal bonds. However, the self-healing ability of metals is too poor, and it is difficult to Solved the transmutation problem."

"Therefore, why don't we set the first wall as a material that allows neutrons to pass through and has a strong self-healing ability, and then use liquid 63 lithium to recover neutrons behind the first wall. As for the other side of 63 lithium, use A coating of beryllium metal to reflect neutrons that pass through the liquid lithium layer unreacted."

This design is equivalent to sandwiching liquid lithium between the first wall and the beryllium.

Sheng Xianfu lowered his head and thought for a while, and felt that this method seemed feasible, but he always felt that there were problems everywhere.

After thinking for a while, he picked out the two most obvious questions from the ones he could think of.

"But where can we find materials that allow neutrons to pass through and have strong self-healing capabilities? Even if the lithium material is moved to the first wall material, we still cannot solve the damage caused by neutron radiation to structural materials. .And, as you say, the tritium is recovered after the first wall, how do we move it back into the reactor from behind the first wall?"

Hearing these two problems, Lu Zhou smiled lightly and said: "The second problem is actually not difficult to solve. At the working temperature of liquid lithium, both tritium and helium exist in gaseous form, and the two are incompatible."

"We only need to apply a weak upward force to the entire liquid lithium neutron recovery system to transport the generated tritium to the top of the entire system."

"Then, we only need to recycle the exhausted 'gas' above the entire system."

The generated tritium and helium as waste gas are re-injected into the reaction chamber to be heated and ionized. As for how to get the helium out of the reactor, that's the job of the divertor.

As for whether to choose a water-cooled divertor or a tungsten-copper divertor or other divertors, it is good to choose according to the specific needs at that time. Although this part of the technology is critical, it is not an unsolvable difficulty.

Speaking of this, Lu Zhou paused, and continued, "As for the first question you mentioned, such a material cannot be found in alloys. So, let's just throw away the metal!"

At the moment of hearing this sentence, not only Sheng Xianfu who asked the question, but also Professor Li Changxia, everyone in the laboratory was stunned.

Abandon metal materials?

This……

This is too avant-garde, right?

"The structural material doesn't use metal?" Professor Li Changxia looked at Lu Zhou in surprise, "Then what?"

Is it ceramic?

Although some research institutes have tried this, and the effect is not bad, but the fatal thing is that the thermal conductivity of ceramics is really poor.

If you can't get the heat generated out of the reactor, something will eventually go wrong.

"Use carbon," Lu Zhou said after a pause, "or to be more precise, use carbon fiber composite materials!"

This is not a method that Lu Zhou came up with on a whim. Before that, he had thought about it for a long time, even when he was chatting with Professor Kleber at the Spiral Stone 7-X Research Institute, he was thinking about it.

The carbon nucleus is relatively stable, not easy to react with neutrons, and can play a certain role in buffering the neutron beam, so that when the neutron beam is in contact with the liquid lithium layer, most neutron beams will not directly break it down .

The part of the energy reduced by the carbon fiber layer will be released in the form of heat energy, and with its good thermal conductivity, it can also easily dissipate the heat generated inside the reactor.

As for the heat resistance performance, it is not a problem at all.

When not in contact with air and oxidants, carbon fiber materials can withstand high temperatures above 3000 degrees, comparable to the melting point of tungsten, and fully meet the needs of the first wall material!

Looking around at the people in the laboratory, Lu Zhou said: "The low-activation metal material is completely removed from the first wall, and carbon fiber is used as the first wall material and the main structural material, and liquid lithium is filled in the middle layer, and the outer layer is used. Beryllium coating, which reflects neutrons. The shielding layer is a mixture of paraffin wax and water and boron carbide, and it is coated with nuclear power cement. In this way, we have full hope of solving the problem of tritium retention!"

As for what kind of carbon fiber composite material to choose and how to solve the problem of self-repair of carbon fiber composite material, this subject will be studied by the Materials Research Institute of Jinling Institute for Advanced Study.

Although the problem is serious, Lu Zhou has hope to solve it!

Professor Li Changxia couldn't help but said: "This is too..."

What he wanted to say was that this was too unbelievable.

But he was only halfway through the sentence when Sheng Xianfu interrupted him.

"No, I'm not sure... There is hope in doing this!"

Interrupting Professor Li's words, Sheng Xianfu kept rubbing his chin with his index finger, and the look in his eyes became brighter and brighter.

"I have checked the relevant literature, and using carbon fiber to replace part of the austenitic steel and tungsten steel structure is a technical route that is equally promising as nano-ceramics in the field of international controllable fusion!"

"However, carbon fiber composite materials are used to completely replace metal materials as the main body of structural materials, and the decelerated neutron beams are placed outside the cladding material to react with liquid lithium, and then the tritium in liquid lithium is recovered through transportation... It’s the first time I’ve heard of this.”

I am afraid that the difficulty is not small, and it is not just a problem of carbon fiber composite materials themselves. such as temperature control. The working temperature of the carbon fiber material of the first wall is about 3000 degrees, while the boiling point of lithium metal is only 1340 degrees.

If the heat cannot be taken away in time, the liquid lithium in the entire "liquid lithium neutron recovery system" will be at risk of being gasified, at least it will be involved in the reactor together with the tritium-helium mixture generated by the reaction, and at the worst it may even destroy the entire The reactor blows up...

There is also the problem of the volume change caused by the solidification of liquid lithium when the reactor is shut down...

But as Lu Zhou said, this idea seems to be feasible.

At least, it's worth a try! -

(I went out to collect materials yesterday, and today there is only one update T.T)