To create an atomic bomb, the critical mass must be reduced and the power of the explosion must be improved. This requires that the atomic bomb must use a fast neutron fission system, the charge must be a high concentration of fission substance, and the charge amount must be greatly exceeded by the critical mass, so that the proliferation coefficient k is much larger than that of the greater than that of the proliferation coefficient k

So far, the three fission substances that can be obtained in large quantities and can be used as atomic bomb charges are limited to 235239 and 233.

The main charge of the 235 atomic bomb. It is not easy to obtain a high concentration of 235, because the natural 235 content is very small, about 140 has 1 235 atom, while the remaining 139 are 238 atoms; especially the isotopes of the same element of 235238, their chemical properties are almost no different, and the relative mass difference between them is also very small. Therefore, it is impossible to separate them by ordinary chemical methods; it is useless to separate light element isotopes.

In order to obtain a high concentration of 235, the 235 subs is about 1.3% lighter than the 23 atoms. Therefore, if these two atoms are allowed to be in a gas state, the 235 atoms will move slightly faster than the 238 subs, and the two atoms can be slightly separated. The gas diffusion method is based on this slight mass difference between 235 subs and 238 subs.

This method first requires conversion to gaseous compounds. So far, hexachloride is the only suitable gaseous compound. This compound is solid at room temperature and pressure, but is easily volatile, and is sublimated into gas at 56.4. Compared with hexachloride molecules of 235, the mass difference between the two is less than one percent, but it turns out that this difference is enough to separate them.

The hexachloride gas is forced to pass through a porous diaphragm under pressure. It contains 235 molecules and passes through the porous diaphragm a little faster, so every time it passes through a porous diaphragm, the oil content of 235 will increase slightly, but the increase is very small. Therefore, to obtain an almost pure 235,::
Chapter completed!