Chapter 1
Energy Release in Nuclear Reactions,
Neutrons, Fission, and Characteristics
of Fission
While this book is not intended to be a history of nuclear physics, it will be helpful
to set the stage by reviewing some relevant discoveries. To this end, we first explore
the discovery of the enormous energy release characteristic of nuclear reactions,
research that goes back to Ernest Rutherford and his collaborators at the opening of
the twentieth century; this is covered in Sect. 1.2. Rutherford also achieved, in 1919,
the first artificial transmutation of an element (as opposed to this happening naturally,
such as in an alpha-decay), an issue we examine in Sect. 1.3. Nuclear reactors and
weapons cannot function without neutrons, so we devote Sect. 1.4 to a detailed
examination of James Chadwick’s 1932 discovery of this fundamental constituent of
nature. The neutron had almost been discovered by Irène and Frédéric Joliot-Curie,
who unfortunately misinterpreted their own experiments. They did, however, achieve
the first instance of artificially induced radioactive decay, a situation we examine in
Sect. 1.5; this section also contains a brief summary of events leading to the discovery
of fission. In Sects. 1.6–1.11 we examine the process of fission, the release of energy
and neutrons during fission, and explore why only certain isotopes of particular heavy
elements are suitable for use in fission weapons. Before doing any of these things,
however, it is important to understand how physicists notate and calculate the energy
liberated in nuclear reactions. This is the topic of Sect. 1.1.
1.1 Notational Conventions for Mass Excess and Q-Values
On many occasions we will need to compute the energy liberated or consumed in a
nuclear reaction. Such energies are known as Q-values; this section develops convenient notational and computational conventions for dealing with such calculations.
Any reaction will involve input and output reactants. The total energy of any
particular reactant is the sum of its kinetic energy and its relativistic mass-energy,
mc
2 . Since total mass-energy must be conserved, we can write
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
B. C. Reed, The Physics of the Manhattan Project,
https://doi.org/10.1007/978-3-030-61373-0_1
1
Energy Release in Nuclear Reactions,
Neutrons, Fission, and Characteristics
of Fission
While this book is not intended to be a history of nuclear physics, it will be helpful
to set the stage by reviewing some relevant discoveries. To this end, we first explore
the discovery of the enormous energy release characteristic of nuclear reactions,
research that goes back to Ernest Rutherford and his collaborators at the opening of
the twentieth century; this is covered in Sect. 1.2. Rutherford also achieved, in 1919,
the first artificial transmutation of an element (as opposed to this happening naturally,
such as in an alpha-decay), an issue we examine in Sect. 1.3. Nuclear reactors and
weapons cannot function without neutrons, so we devote Sect. 1.4 to a detailed
examination of James Chadwick’s 1932 discovery of this fundamental constituent of
nature. The neutron had almost been discovered by Irène and Frédéric Joliot-Curie,
who unfortunately misinterpreted their own experiments. They did, however, achieve
the first instance of artificially induced radioactive decay, a situation we examine in
Sect. 1.5; this section also contains a brief summary of events leading to the discovery
of fission. In Sects. 1.6–1.11 we examine the process of fission, the release of energy
and neutrons during fission, and explore why only certain isotopes of particular heavy
elements are suitable for use in fission weapons. Before doing any of these things,
however, it is important to understand how physicists notate and calculate the energy
liberated in nuclear reactions. This is the topic of Sect. 1.1.
1.1 Notational Conventions for Mass Excess and Q-Values
On many occasions we will need to compute the energy liberated or consumed in a
nuclear reaction. Such energies are known as Q-values; this section develops convenient notational and computational conventions for dealing with such calculations.
Any reaction will involve input and output reactants. The total energy of any
particular reactant is the sum of its kinetic energy and its relativistic mass-energy,
mc
2 . Since total mass-energy must be conserved, we can write
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
B. C. Reed, The Physics of the Manhattan Project,
https://doi.org/10.1007/978-3-030-61373-0_1
1