![]() Two hemispheres which are explosively forced into contact can produce a bomb such as the one detonated at Hiroshima. This leads to an almost instantaneous buildup of the chain reaction, creating a powerful explosion before the pieces can fly apart. Then the pieces must be forced together quickly and in such a geometry that the generation time for fission is extremely short. Once the required mass is obtained, it must be kept in two or more pieces until the moment of detonation. This enrichment is an exceptionally difficult task, a fact that has helped control the proliferation of nuclear weapons. First you must obtain enough uranium which is highly enriched to over 90% U-235, whereas natural uranium is only 0.7% U-235. That is not to say that this is an easy task to accomplish. Using the energy release from the nuclear fission of uranium-235, an explosive device can be made by simply positioning two masses of U-235 so that they can be forced together quickly enough to form a critical mass and a rapid, uncontrolled fission chain reaction. Analysis of the radioactive fallout from this bomb revealed it to be a fission-fusion-fission weapon, a "hydrogen bomb" with an outer sheath of natural uranium to increase the yield. It had a fireball 4.8 km in diameter and created a huge characteristic mushroom-shaped cloud. exploded a 15 megaton fusion bomb on March 1, 1954. The Soviet Union detonated a fusion bomb in the megaton range in August of 1953. The first hydrogen bomb was detonated on Novemat the small island Eniwetok in the Marshall Islands. Then the deuterium-tritium fusion reaction could take place.īecause the thermonuclear explosive devices used hydrogen isotopes, ( deuterium-tritium fusion), the resulting bombs were often called "hydrogen bombs". In the process, the lithium was bombarded with neutrons, breeding tritium. The only way which was found to produce the ignition temperature was to set off a fission bomb such that it would heat and compress the lithium hydride. To obtain the two parts of the fuel, pellets were made from lithium hydride, LiD, made with the deuterium isotope. This led to the term "hydrogen bomb" to describe the deuterium-tritium fusion bomb. ![]() This is typically done with the isotopes of hydrogen, deuterium and tritium. A thermonuclear explosion can be created only by producing the required temperature, about a hundred-million Kelvins, and by forcing the material together so quickly that it will fuse rapidly. Because of the high temperatures required to initiate a nuclear fusion reaction, such devices are often called thermonuclear devices.
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