The atomic bomb is an extremely lethal weapon, which is not easy to use in modern wars because the consequences are unimaginable. Nuclear weapons have unique destructive power such as strong shock wave, optical radiation, early nuclear radiation, radioactive contamination and nuclear electromagnetic pulse. At present, American Militia 3 has an equivalent of almost 500,000 tons. Imagine the explosion of 500 thousand tons of TNT explosive. After the explosion, there were all kinds of nuclear radiation pollution. For a long time, nothing grew in that place.

1In August, 945, the atomic bomb (code name "Little Boy") dropped by the United States in Hiroshima, Japan, adopted a gun structure, weighing about 4 100 kg, with a diameter of about 7 1 cm and a length of about 305 cm. The nuclear charge is uranium 235, and the explosive power is about 14000 tons TNT equivalent. Finally, let's take a look at the moment when the "little boy" threw himself into Hiroshima.

The atomic bomb is mainly composed of detonation control system, explosive, reflecting layer, nuclear components composed of nuclear charge, nuclear ignition components and shell. Detonation control system is used to detonate explosives in time, and it is the energy to push and compress the reflective layer and nuclear components. The reflective layer is made of beryllium or uranium -238 to reduce neutron leakage; The nuclear charge is mainly uranium -235 or uranium-239; The nuclear ignition assembly is used to provide "ignition" neutrons to trigger the chain reaction of nuclear fission; Shell casings are used to fix and assemble parts.

1 kg uranium -235 releases nearly 20,000 tons of TNT explosive after fission (the picture is incorrect)! If you pull by train, you need more than 340 carriages, and the train is 5.2 kilometers long!

According to the different initiation mechanism of atomic bombs, atomic bombs can be divided into "gun type" and "convergent type (implosion type)". Modern atomic bombs usually combine the characteristics of these two structures to improve the utilization rate of nuclear charges and enhance the destructive power.

Uranium is a heavy metal element. There are three isotopes in natural uranium, arranged by mass number. They are uranium-238, uranium-235 and uranium-234, which constantly radiate α, β and γ rays to the outside world. The abundance of isotope uranium 235 in natural uranium is only 0.72%, which must be increased to more than 90% according to the design requirements of atomic bombs. Uranium 235 with particle size over 95% has

But this atomic bomb the size of a grain of rice will not explode, because the prerequisite for the atomic bomb explosion is that the quality of uranium metal is large enough. The volume of each piece of uranium is less than the critical volume (the volume of uranium 235 is not less than the critical volume, which is another necessary condition for chain reaction), so it usually does not explode.

Nuclear power charges for several hours and is small in size. If the generated neutrons do not hit other nuclei, they may run out of the nuclear charge and interrupt the chain reaction, and the energy released by nuclear fission of a single uranium atom is very small. Only when a large number of uranium nuclei continue to fission, which is commonly called chain reaction, can a large amount of energy be obtained.

In other words, an atomic bomb the size of a grain of rice is just a radioactive metal block, which can't meet the explosion standard, but it is radioactive enough to make people close to it sick and die. Uranium is a heavy metal with obvious nephrotoxicity. The enriched uranium used to make atomic bombs is 90%, so it can't be approached or directly contacted.