The design of modern BWR assemblies is governed by general requirements such as safe and reliable performance, optimal fuel utilization and cycle length, and a high degree of flexibility in reactor operation. These requirements are fulfilled via the use of increased enrichments, high gadolinium loadings and part-length fuel rods, which lead to very heterogeneous assembly designs, causing not only large variations in the power density of individual fuel pins, but also strong radial and azimuthal gradients in reaction rate distributions within the pins themselves. The invasive technique of activation foils (depleted uranium) is applied and the experimental results are compared with calculations performed using the deterministic code CASMO-4 as well as the stochastic code MCNP