Two places where Japan's atomic bomb exploded

1945 On August 6th, Ainola Gay, a B-29 super robotech bomber piloted by Paul Tibbets, dropped 3 1000 feet (9000m) over Hiroshima. At 8: 00 a.m. 15 local time in Japan, it exploded at a height of 1 1,800 feet (550 meters). More than 200,000 people were killed or injured; On August 9, the second "fat man" was cast in Nagasaki.

The explosion of nuclear weapons not only releases huge energy, but also the nuclear reaction process is very rapid and can be completed in microseconds. Therefore, extremely high temperature is formed in a small area around the explosion of nuclear weapons, and the surrounding air is heated and compressed to expand rapidly, resulting in high-pressure shock waves. Nuclear explosions on the ground and in the air will also form fireballs in the surrounding air, giving off strong optical radiation. Nuclear reaction will also produce all kinds of rays and radioactive material fragments; The intense pulse rays radiated outward interact with the surrounding substances, causing the process of current growth and disappearance, resulting in electromagnetic pulses. These characteristics, which are different from the explosion of chemical explosives, make nuclear weapons have unique destructive effects such as strong shock wave, optical radiation, early nuclear radiation, radioactive contamination and nuclear electromagnetic pulse. The emergence of nuclear weapons has had a great impact on the strategy and tactics of modern warfare.

The atomic bomb is mainly a weapon that uses the huge energy released by nuclear fission to kill. It is based on the same nuclear fission chain reaction as a nuclear reactor. It stands to reason that since the reactor can realize chain reaction, as long as its neutron multiplication coefficient k is greater than 1, the scale of chain reaction will become larger and larger without control, and eventually an explosion will occur. In other words, the reactor can also become an "atomic bomb". Actually, it's the same. If the multiplication coefficient k is greater than 1, the reactor will indeed explode without control. The so-called super-criticality accident reactor is such a situation. The reactor weighs 100 tons and can't be used as a weapon. Moreover, in this case, the utilization rate of fissile materials is very low and the explosive power is not great. To make an atomic bomb, we must first reduce the critical mass and at the same time improve the explosive power. This requires that the atomic bomb must use a fast neutron fission system, the charge must be high-concentration fissile material, and the charge must greatly exceed the critical mass, so that the multiplication coefficient K is much greater than 1.

The explosive quantity of an atomic bomb can be obtained in large quantities, and the explosive quantity that can be used as an atomic bomb is limited to three fissile materials: uranium 235, plutonium 239 and uranium 233. Uranium 235 is the main charge of the atomic bomb. It is not easy to obtain high concentration of uranium -235, because the content of natural uranium -235 is very small. About 140 uranium atoms only contain 1 uranium -235 atoms, while the rest 139 are all uranium -238 atoms. In particular, uranium 235 and uranium 238 are isotopes of the same element, with almost the same chemical properties and little relative mass difference.