Radiation Hardened By Design (RHBD) SRAM-based FPGAs are getting more and more appealing for space applications, since they embed mitigation techniques in the device itself, masking their complexity to the end-user. However, over a certain LET, this kind of devices could not guarantee hardening against radiation. It is thus necessary to perform a robustness analysis even for this kind of device. Computing the Single Event Upsets (SEU) sensitivity of the FPGA by means of the device cross-section is very pessimistic. So, we propose and validate a static analysis approach to asses the application-oriented cross-section, providing evidence on a soft processor core. The analysis is performed in a modular fashion, reporting the sensitivity of the different modules that compose the processor. Finally, results for a real environment and mission are reported, presenting the benefits of the proposed approach.