Neutron Bomb

The Mark 17 hydrogen bomb: the largest bomb ever made by the United States. Over 24 feet long, 42,000 pounds, and with an explosive power of 15-20 megatons (equivalent to over 1,000 Hiroshima size bombs). This one is on display at the National Atomic Museum. CLUI photo
Neutron Bomb
    Neutron bombs, more formally referred to as "enhanced radiation (ER) warheads", are small thermonuclear weapons in which the burst of neutrons generated by the fusion reaction is intentionally not absorbed inside the weapon, but allowed to escape.
    Neutron bombs differ from other thermonuclear weapons in that a deuterium-tritium gas mixture is the only fusion fuel. There are 2 reasons: the D-T thermonuclear reaction releases 80% of its energy as neutron kinetic energy, and it is also the easiest of all fusion reactions to ignite. This means that only 20% of the fusion energy is available for blast and thermal radiation production, that the neutron flux produced consists of extremely penetrating 14.7 Mev neutrons, and that a very small fission explosion (250-400 tons) can be used for igniting the reaction. The more typical lithium deuteride fuel would produce much more blast and flash for each unit of neutron flux, and would require a much larger fission explosion to set it off. The disadvantage of using D-T fuel is that tritium is very expensive, and decays at a rate of 5.5% a year. Combined with its increased complexity this makes ER warheads more expensive to build and maintain than other tactical nuclear weapons. To produce a 1 Kt fusion yield 12.5 g of tritium and 5 g of deuterium are required.
    The U.S. developed and produced three neutron warheads, a fourth was cancelled prior to production. All have been retired and dismantled.
    The Soviet Union, China, and France are all known to have developed neutron bomb designs and may have them in service. A number of reports have claimed that Israel has developed neutron bombs which, though they could be valuable on an armor battleground like the Golan Heights, are difficult to develop and require significant testing. This makes it unlikely that Israel has in fact acquired them.