Chapter 3 - Building Block Fluxes for the General Equation Set

Abstract

This chapter focuses on the building blocks required to describe the nuclear and physicochemical processes in the general equation set. The building block equation needed to construct the general equation set is familiar to all nuclear engineers. Its form is the same no matter which dependent variable is being balanced, so it is illustrated using abbreviated ferrite layer variables. All activation reactions could be described with a single production cross-section and a thermal neutron flux. This was done in an attempt to minimize the amount of user-defined inputs that would be required to describe the nuclear processes within the reactor over the entire lifetime of the problem simulation. To accomplish this, the nuclear modeling of the ORIGEN computer program was selected because it allows the user to create an effective thermal neutron production cross-section using three flux shaping parameters. Using this system, the user only need specify the three flux shaping parameters and the thermal neutron flux for every part of the hydraulic flow path where there is a significant neutron activating flux. Generally, these inputs are only needed for parts of the hydraulic circuit that are inside the reactor vessel.