AbstractThe efficient use of nodal methods for three-dimensional two-group reactor calculations requires homogenization over large volumes or nodes. This homogenization removes the internal structure of the nodes. On the other hand, accurate pinwise power distributions are indispensable for light water reactor design. A homogenization and dehomogenization procedure called the simplified equivalence theory (SET) has been proposed, which allows the accurate and inexpensive determination of pinwise power distributions of fresh reactor cores. The SET procedure is extended to burnup and parameter dependencies. For the case of fuel assembly homogenization and dehomogenization, this extension is validated by a procedure that allows assessment of the accuracy of the method, referring exclusively to the spectral geometry of the assembly. For the validation of the equivalent reflector model, a nodal reactor test problem is set up which shows that this model is adequate to describe core/reflector interactions under burnup conditions.