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The reaction energy (the "Q-value") is positive for exothermal reactions and negative for endothermal reactions, opposite to the similar expression in chemistry. On the one hand, it is the difference between the sums of kinetic energies on the final side and on the initial side.
A positive void coefficient means that the reactivity increases as the void content inside the reactor increases due to increased boiling or loss of coolant; for example, if the coolant acts predominantly as neutron absorber. This positive void coefficient causes a positive feedback loop, starting with the first occurrence of steam bubbles ...
A reaction with a negative Q value is endothermic, i.e. requires a net energy input, since the kinetic energy of the final state is less than the kinetic energy of the initial state. [1] Observe that a chemical reaction is exothermic when it has a negative enthalpy of reaction, in contrast a positive Q value in a nuclear reaction.
It is the reaction which occurs when a neutron enters a nucleus and a proton leaves the nucleus simultaneously. [1] For example, sulfur-32 (32 S) undergoes an (n,p) nuclear reaction when bombarded with neutrons, thus forming phosphorus-32 (32 P). The nuclide nitrogen-14 (14 N) can also undergo an (n,p) nuclear reaction to produce carbon-14 (14 C).
A positive value of U is due to a repulsive force, so interacting particles are at higher energy levels as they get closer. A negative potential energy indicates a bound state (due to an attractive force). The Coulomb barrier increases with the atomic numbers (i.e. the number of protons) of the colliding nuclei:
The mass excess of a nuclide is the difference between its actual mass and its mass number in daltons.It is one of the predominant methods for tabulating nuclear mass. The mass of an atomic nucleus is well approximated (less than 0.1% difference for most nuclides) by its mass number, which indicates that most of the mass of a nucleus arises from mass of its constituent protons and neutrons.
A table or chart of nuclides is a two-dimensional graph of isotopes of the elements, in which one axis represents the number of neutrons (symbol N) and the other represents the number of protons (atomic number, symbol Z) in the atomic nucleus. Each point plotted on the graph thus represents a nuclide of a known or hypothetical chemical element.
When certain components or parameters change the reactivity of a nuclear reactor, the changes may be calculated as their reactivity worth. A control rod and a chemical reactor poison both have negative reactivity worth, while the addition of a neutron moderator would generally have a positive reactivity worth. Reactivity worth can be measured ...