Author Archives: sidefive

Understanding Radiation: Scientific Basis of Nuclear Explosions – Thermal Radiation

The observed phenomena associated with a nuclear explosion and the effects on people and materials are largely determined by the thermal radiation and its interaction with the surroundings. It is desirable, therefore, to consider the nature of these radiations somewhat further. Thermal radiations belong in the broad category of what are known as “electromagnetic radiations.” These are a kind of ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Time Scale of a Fission Explosion

An interesting insight into the rate at which the energy is released in a fission explosion can be obtained by treating the fission chain as a series of “generations.” Suppose that a certain number of neutrons are present initially and that these are captured by fissionable nuclei; then, in the fission process other neutrons are released. These neutrons, are, in ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Thermonuclear Fusion Reactions

Energy production in the sun and stars is undoubtedly due to fusion reactions involving the nuclei of various light (low atomic weight) atoms. From experiments made in laboratories with charged-particle accelerators, it was concluded that the fusion of isotopes of hydrogen was possible. This element is known to exist in three isotopic forms, in which the nuclei have mass numbers ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Fission Products

Many different initial fission product nuclei, i.e., fission fragments, are formed when uranium or plutonium nuclei capture neutrons and suffer fission. There are 40 or so different ways in which the nuclei can split up when fission occurs; hence about 80 different fragments are produced. The nature and proportions of the fission fragment nuclei vary to some extent, depending on ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Fission Energy

The significant point about the fission of a uranium (or plutonium) nucleus by means of a neutron, in addition to the release of a large quantity of energy, is that the process is accompanied by the instantaneous emission of two or more neutrons; thus, __________________________________________________________ Table 6-1. Neutron + uranium-235 = fission fragments + (or uraniurn-233) 2 or 3 neutrons ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Critical Mass for a Fission Chain

Although two to three neutrons are produced in the fission reaction for every nucleus that undergoes fission, not all of these neutrons are available for causing further fissions. Some of the fission neutrons are lost by escape, whereas others are lost in various nonfission reactions. In order to sustain a fission chain reaction, with continuous release of energy, at least ... Read More »

Understanding Radiation: Scientific Basis of Nuclear Explosions – Attainment of Critical Mass in a Nuclear Weapon

Because of the presence of stray neutrons in the atmosphere or the possibility of their being generated in various ways, a quantity of a suitable isotope of uranium (or plutonium) exceeding the critical mass would be likely to melt or possibly explode. It is necessary, therefore, that before detonation, a nuclear weapon should contain no piece of fissionable material that ... Read More »

Understanding Radiation: Residual Radiation

The residual radiation hazard from a nuclear explosion is in the form of radioactive fallout and neutron-induced activity. Residual ionizing radiation arises from: Fission Products These are intermediate weight isotopes which are formed when a heavy uranium or plutonium nucleus is split in a fission reaction. There are over 300 different fission products that may result from a fission reaction. ... Read More »

Understanding Radiation and Fallout

Fallout is simply the dirt and dust which falls to the ground following a nuclear explosion. It will “charged” with radiation and will eventually “burn” itself out – a process that will take several days. Radioactive fallout will fall in a manner similar to that following a volcanic eruption. It will be flaky in appearance and its size may reduce ... Read More »

Understanding Radiation: Initial Radiation

About 5% of the energy released in a nuclear air burst is transmitted in the form of initial neutron and gamma radiation. The neutrons result almost exclusively from the energy producing fission and fusion reactions, while the initial gamma radiation includes that arising from these reactions as well as that resulting from the decay of short-lived fission products. The intensity ... Read More »