Nodal formulation relating assembly power and reactivity

Although nodal methods for light water reactor physics calculations have long been part of the fuel manager's repertoire, most involve computation of the neutron flux given cross-section data as input. Work at the Massachusetts Institute of Technology by a number of students over the past several years has shown that it is sometimes advantageous to formulate nodal relations that directly compute node (e.g., assembly) average power given reactivity as input. For example, since (poison-free) reactivity is, to an excellent approximation, a linear function of burnup, a nodel model of this type is ideally suited as a module in core reload optimization computations, since they typically require many rapid calculations shuttling back and forth between the beginning and end of cycle for a variety of loading patterns. The approach is also particularly useful for teaching purposes