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Iteration Methods with Multigrid in Energy for Eigenvalue Neutron Diffusion Problems
Published in Nuclear Science and Engineering, 2019
Luke R. Cornejo, Dmitriy Y. Anistratov, Kord Smith
The phase-space of neutron transport problems has high dimensionality. It includes the spatial position of the particle, its energy, and the direction of particle motion. In general, it is a six-dimensional space. To reduce the dimensionality of the problem and complexity of neutron transport simulations, various approximate methods have been developed. One group of neutron transport models is based on the P1 equations that belong to the family of the method of spherical harmonics also known as the PN method.2 In neutron transport theory it is common to formulate the Boltzmann equation for the neutron angular flux, which is the product of the distribution function and the particle speed. The P1 equations are defined for the first two moments of the neutron angular flux and hence of the distribution function. The moment equations are closed assuming that the angular flux linearly depends on the direction of particle motion. The P1 equations can be reduced to the neutron diffusion equation for the zeroth angular moment of the angular flux.