An apparatus generating a graphical image of a core of a boiling water reactor (BWR) using at least one data set of channel deformation data including: a computer system including a display device for presenting the graphical image and a processor generating the graphical image using the at least one data set; the graphical image of the core includes symbolic representations of control blades arranged in the core, indicia identify each control blade, and indicia regarding deformation of channels adjacent each control blade, and a viewer software tool executed by the processor which accesses the at least one data set and determines a location in the core of the control blades and channels, and correlates the deformation data with the channels for display on the graphical image.