12dz Chapter 145 Explaining the Refining Method
Chapter 145 Explaining the Refining Method
When the helicopter returned to the base, Zhang Tian immediately arranged for people to place the uranium ore under a specially built basement.
Then call everyone to a meeting.
Next, we will prepare to deal with the uranium ores.
Everything is ready. Now we need to start extracting the key material, uranium 235, and figure out how to make it react and fission.
There were more than a dozen people sitting in the small conference room.
These are the core members of this project.
Zhang Tian said, "Everyone, we have brought back the uranium ore, but the next step is our focus."
The people below nodded.
Indeed, the next step is to start extracting and reflecting those tasks.
An expert stood up and asked, "Director Zhang, I know a little about nuclear fission. I would like to ask, what value do you plan to use for fission?"
You can tell whether Youdao is an expert just by listening to him.
Zhang Tian smiled at the expert and nodded secretly in his heart.
This hits the point.
What needs to be extracted is the nucleus of uranium-235, but there is a problem here.
These ores also contain uranium-238.
The value 238 sounds higher than 235, but it is not suitable for use in nuclear weapon manufacturing.
In terms of its fissile properties, uranium-235 is a fissile nuclide. After absorbing a slow neutron, it can undergo a fission reaction, releasing huge amounts of energy and multiple neutrons, thereby triggering a chain reaction.
This allows uranium-235 to continuously undergo controlled nuclear fission in a nuclear reactor, providing a stable energy output for the nuclear energy below.
Although uranium-238 can also undergo nuclear reactions, it is not easy to undergo fission reactions directly.
In terms of fission efficiency, the energy released by 235 during fission is relatively high, and the energy released by the fission of each 235 atom is about 200 MeV.
In contrast, the energy released by uranium-238 fission is relatively low, and it is difficult to directly initiate a fission reaction.
For nuclear weapon manufacturing, the rapid chain fission reaction of uranium-235 can release huge explosive energy.
This is much faster than 238.
As for separation and enrichment, although separating and enriching uranium-235 from natural uranium is a complex and costly technology, there are relatively mature methods at present, such as gas diffusion and centrifugation.
These methods can increase the concentration of uranium-235 in natural uranium to levels that meet the needs of nuclear reactors and nuclear devices.
The separation and utilization of uranium-238 is relatively technically difficult.
Moreover, since the fission reaction of uranium-235 is relatively easy to control, the number and energy of neutrons can be adjusted through devices such as control rods, thereby achieving precise control of the nuclear reaction.
The nuclear reaction characteristics of 238 make it more difficult to control its reaction.
Therefore, they must be separated.
The slight difference in mass between uranium-235 and uranium-238 is used to separate them through physical methods.
One of the commonly used methods is gas diffusion.
That is, the uranium compounds are converted into gas and then diffused through a porous membrane. Since 235 is slightly lighter, it will diffuse slightly faster, thus achieving separation from 238.
Zhang Tian smiled and said, "Professor Chen, based on this value, we still prefer the value of 235. I have decided to use the gas diffusion separation method."
After Zhang Tian finished speaking, he took out a stack of information from his bag.
He then said, "This is a complete document on the gas separation method. It not only includes the use of the equipment but also the operating steps."
"Let me briefly explain it below."
When Zhang Tian was about to explain, the experts below all became serious.
The wise are the teachers. Maybe they are the best in other fields, but they are really not as good as Zhang Tian in this aspect.
Zhang Tian said, "We start with uranium ore and crush it to make its particles smaller so that it can fully react with chemical reagents later."
"The crushed uranium ore is mixed with reagents such as sulfuric acid, and the uranium in the ore reacts with the sulfuric acid to produce soluble uranium compounds, such as uranyl ions."
"For uranium ores containing carbonates, aqueous solutions of sodium carbonate and sodium bicarbonate are often used for leaching under the condition of blowing air, so that the uranium in the ore reacts with sodium carbonate to form soluble substances such as sodium uranyl carbonate."
"The acidic or alkaline slurry containing uranium (including uranium-containing solution, some impurities and solid slag) obtained after leaching is separated. Commonly used solid-liquid separation equipment includes filters, sedimentation tanks (thickeners), etc."
"Then through a series of operations such as extraction and precipitation, most of the impurities are removed to obtain relatively pure uranium-containing compounds."
The obtained uranium-containing compound is further reacted with hydrofluoric acid and fluorine gas to be converted into uranium hexafluoride. Uranium hexafluoride is solid at room temperature and pressure, but it is easy to volatilize and sublimate into gas at 56.4 degrees Celsius, which is convenient for subsequent gas diffusion operations.
The diffusion device contains a diffusion membrane (separation membrane) with countless micropores that allow molecules to pass through. The size of these micropores needs to be carefully designed to ensure that gas molecules do not collide with each other as much as possible and can be separated according to differences in molecular weight.
Generally, the pore size of the diffusion membrane should be smaller than the mean free path of molecular motion.
The prepared uranium hexafluoride gas is then flowed under pressure into a device equipped with a diffusion membrane.
Due to molecular thermal motion, the average thermal motion rate of the lighter uranium-235 uranium hexafluoride molecules is slightly faster than that of the slightly heavier uranium-238 uranium hexafluoride molecules, so the uranium-235 uranium hexafluoride molecules have a greater chance of passing through the diffusion membrane.
After passing through the diffusion membrane, two streams are formed, one is a gas flow relatively rich in uranium-235, and the other is a gas flow relatively depleted in uranium-235, thus achieving a certain degree of isotope separation.
However, the separation effect of single-stage diffusion is limited, and the enrichment level of uranium-235 is not high.
In order to increase the enrichment level of uranium-235, multiple diffusion devices need to be connected in series to form a multi-stage diffusion system.
The uranium-235-rich gas flow coming out of the previous stage diffusion device enters the next stage diffusion device for further separation, while the uranium-235-depleted gas flow can be processed according to the situation, such as partially returning to the previous stage for reuse.
After thousands of separations, the concentration of uranium-235 is gradually increased to the required level.
At the outlet of each stage of the diffusion device, uranium-235-rich gas and uranium-235-depleted gas are collected separately.
The uranium-235-rich gas is further processed and enriched to eventually produce a high-concentration uranium-235 product that can be used in nuclear reactors and other fields.
After Zhang Tian finished speaking, he also asked Wang Hui to post the specific steps on the wall in the form of pictures in order.
"If there are no problems, then let's get started."
"The mushroom cloud must be born in our hands."