A particular nuclide is characterized by its atomic number Z (the number of protons) and its nucleon number A (the total number of protons and neutrons). The isotopes of an element have the same atomic number but different numbers of neutrons.
The mass density of all nuclei is approximately the same The radius of a nucleus is
r = r0A1/3
(29-4)
where r0 = 1.2 × 10-15 m = 1.2 fm
(29-5)
The binding energyEB of a nucleus is the energy that must be supplied to separate a nucleus into individual protons and neutrons. Since the nucleus is a bound system, its total energy is less than the energy of Z protons and N neutrons that are far apart and at rest.
EB = Δmc2
(29-8)
In any nuclear reaction, the total electric charge and the total number of nucleons are conserved.
An unstable or radioactive nuclide decays by emitting radiation.
The absorbed dose is the amount of radiation energy absorbed per unit mass of tissue, measured in grays (1 Gy = 1 J/kg) or rads (1 rad = 0.01 Gy).
The quality factor (QF) is a relative measure of the biological damage caused by different kinds of radiation. The biologically equivalent dose in rem is
Biologically equivalent dose (in rem) = Absorbed dose (in rad) × QF
(29-29)
A large nucleus can release energy by splitting into two smaller, more tightly bound nuclei in the process called fission. The energy released in a fission reaction is enormous—typically around 200 MeV for the split of a single nucleus.
Nuclear fusion combines two small nuclei to form a larger nucleus. Fusion typically releases significantly more energy per nucleon than fission.
