Overall neutron balance

The neutron source referred to above is a normal component of a nuclear reactor core, which produces a stream of neutrons, 5, per second per m of core, independent of the operating power of the reactor. Such a source is included both to initiate the chain reaction at first start-up and to ensure that the neutron flux detectors will always have a recognizably valid signal to detect even when the reactor is shut down. 

using the definition of reactivity given in equation (21.9), the rate of change of neutron density is  

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Although atoms contain electrically charged particles, the atoms themselves are electrically neutral (they have no overall electric charge). This is because atoms contain equal numbers of electrons and protons. For example, the diagram in Figure 3.3 represents the atom of the non-metallic element helium. The atom of helium possesses two protons, two neutrons and two electrons. The electrical charge of the protons in the nucleus is, therefore, balanced by the opposite charge of the two electrons. 

To demonstrate the importance of the golden ratio it is assumed that protons and neutrons occur in the nucleus on three-dimensional spirals of opposite chirality, and balanced in the ratio Z/N = r, about a central point. The overall ratio for all nuclides, invariably bigger than r, means that a number of protons, equal to Z — Nt, will be left over when all neutrons are in place on the neutron spiral. These excess protons form a sheath around the central spiral region, analogous to the valence-electron mantle around the atomic core. The neutron spiral is sufficient to moderate the coulomb repulsion while the surface layer of protons enhances the attraction on the extranuclear electrons. 

Prove that the overall reaction and the three outcome reactions are balanced for protons and neutrons. 

The core or nucleus of the atom consists of protons and neutrons with electrons travelling in orbits around the nucleus Figure 24.1). Elements normally have no overall charge since the number of protons is matched by an equal number of electrons. However, it is possible to upset this balance by removing either a proton or an electron resulting in the atom carrying a charge when it is said to be ionised. 

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