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Cross Section Libraries and Sources of Nuclear Data
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
Most of the thermal neutron cross sections that we have used so far are based on a specific assumption regarding the shape of the thermal neutron flux. When fast neutrons eventually become thermal neutrons, the number of them that are available to react at a particular energy E becomes a function of only the neutron temperature T. If n is the number of thermal neutrons per cubic centimeter, then these neutrons will populate the thermal energy range between about E = 0 and E = 1 eV according to a statistical probability distribution that is known as the Maxwell–Boltzmann probability distribution. The reader was first introduced to the shape of this distribution in Chapter 4, and some additional information regarding it was provided at the time. The basic shape of this distribution is shown in Figure 5.3, and the equation that governs the probability distribution of the thermal neutrons that it contains is
Bifurcation Analysis of Spatial Xenon Oscillations in Large Pressurized Heavy Water Reactors Using Multipoint Reactor Kinetics with Thermal-Hydraulic Feedback
Published in Nuclear Science and Engineering, 2021
Abhishek Chakraborty, Suneet Singh, M. P. S. Fernando
In PHWRs, the coolant and the moderator are separated, the coolant being at high temperature and pressure and the moderator being at low temperature and pressure.22 Most of the neutrons are in thermal equilibrium with the moderator temperature. When the coolant temperature is increased, the thermal neutron temperature also increases inside the coolant and fuel henceforth hardening the neutron energy spectrum. The coolant temperature coefficient of reactivity is negative for a fresh core and positive for an equilibrium core.21 Hence, for a given reactor core size, the fuel and coolant temperature coefficients of reactivity are a function of burnup and hence change with the operation conditions, and the stability of the spatial xenon oscillations has to be analyzed.