The nuclear reactions that are used for energy production are also used for military purposes. Nuclear weapons utilize both the fusion reaction and the combination of the fusion and fission reactions.

In the fission bomb (better known as the atomic bomb), the unregulated fission of 235U (Eq. (6.21)) or another fissile, plutonium, takes place. The fissile is placed in pieces, each containing less fissile than the critical mass. The chain reaction is ignited by a chemical explosion, which causes the addition of the pieces so that the mass will become more than the critical mass. During the unregulated chain reac­tion, the very high energy of the fission reaction releases in a very short time, caus­ing another explosion. As mentioned in Chapter 1, the first two nuclear bombs were exploded at the end of World War II in Japan. On August 6, 1945, a bomb known as “Little Boy” was exploded in Hiroshima; the fission of 235U took place in the bomb. On August 9, 1945, the “Fat Man” bomb was detonated in Nagasaki; the fissile in this bomb was plutonium.

The combination of the fusion and fission reactions is the thermonuclear or hydrogen bomb. The first hydrogen bomb was developed in 1952. The high tem­perature needed for the ignition of the fusion reaction of hydrogen isotopes (deute­rium and tritium; see Eqs. (6.47) through (6.50)) is provided by a fission reaction; that is, by an atomic bomb. The fusion fuel is tritium, deuterium, or lithium deuter — ide. As mentioned in Section 6.2.4, the ignition temperature is the lowest for the 2H—3H reaction; so the most favorable fusion reaction is the 2H—3H reaction. The production of tritium, however, is expensive, and in addition, its half-life is 12.4 years. For this reason, lithium deuteride is frequently used. From lithium, tritium is produced in the reaction (6.17) under the effect of neutrons formed in the fission reaction.

Recently, fission—fusion—fission bombs have been developed. In these bombs, there is an outer mantle, and the fission reaction takes place. In the so-called salted bombs, the nuclear weapon is surrounded by a substance such as cobalt or gold, from which radioactive isotopes are formed via the nuclear reactions initiated by neutrons that are produced in the fission reactions. These bombs can be considered “dirty bombs” because of their high radioactive contamination.

A special type of thermonuclear weapon is the neutron bomb, in which the fis­sile has low critical mass (e. g., californium). The fusion fuel is the mixture of deu­terium and tritium. The bomb is surrounded by a substance that has a very low level of neutron absorption. In this way, the main destructive impact is caused by the escaping neutrons. The mass of the neutron bombs is only a few kilograms, and therefore it can be transported very easily. Because of the small quantity of fissile, the radioactive contamination is relatively low.

Further Reading

Choppin, G. R. and Rydberg, J. (1980). Nuclear Chemistry, Theory and Applications. Pergamon Press, Oxford.

Friedlander, G., Kennedy, J. W., Macias, E. S. and Miller, J. M. (1981). Nuclear and Radiochemistry. Wiley, New York, NY.

Lieser, K. H. (1997). Nuclear and Radiochemistry. Wiley-VCH, Berlin.

McKay, H. A.C. (1971). Principles of Radiochemistry. Butterworths, London.

Prawitz, J. and Rydberg, J. (1958). Composition of products formed by thermal neutron fission of 235U. Acta Chim. Scand. 12:369—377.

Vajda, N. (1994). Atomreaktorok futoelmeinek ellencSrzeise uj analitikai mcidszerek segitsegevel (Analysis of nuclear fuel elements by new methods). Candidate’s Thesis. Budapet Technical University, Budapest.

European Nuclear Society, 2003. Nuclear power plants, world-wide. < www. euronuclear. org/info/encyclopedia/n/nuclear-power-plant-world-wide. htm (IAEA, August 2011). > (accessed 25.03.12.)