10.13. A commercial operating reactor requires refueling every year or so in accordance with plans made a year or more in advance. In-core fuel management is concerned with the design of such fuel reload packages. Generally, the objective is to minimize the utility’s energy generation cost while staying within a number of safety-related design constraints and materials limitations. However, we will see that the task is challenging, not only because of the large number of design parameters that require attention, but also as a result of changes in constraints made from year to year as the technology improves. Thus, earlier designs are useful only as general guides.

10.14. For the reload core design, a neutronic model is needed of each assembly covering the operating cycle from fuel loading to removal. Con­
tributing to the model are core thermal-hydraulics and reactivity effects. Also relevant is the operating economics of the electric utility generating system. Hence, the picture is complicated. Our purpose here is to provide an initial understanding of both the design challenge and current practice with emphasis given to light-water reactors, particularly the pressurized — water reactor concept.