Runaway electrons (REs) are known to be a significant threat to the integrity of Plasma Facing Components [1]. For this reason, predictive modelling of wall damages induced by REs is crucial for the safe operation of future tokamaks. Recent modelling work using the JOREK [2] code has assessed the RE load distribution on the ITER first wall [3], yielding detailed information on the incidence angle and the energy of the REs for a given wall element. Based on these simulations, the volumetric energy deposition from REs in the material for localized regions of the ITER first wall [4] has been studied. To model RE impacts, [4] uses a two-step approach: Monte Carlo (MC) simulations of the energy deposition in the material, which in turn provide the volumetric source for heat transfer simulations, using the Geant4 and MEMENTO codes. The combination of large tangential scales with very high in-depth resolution makes the Geant4 simulations computationally demanding. Moreover, the MEMENTO simulations also require high in-depth resolution to resolve steep gradients in the volumetric source and erosion of the free surface due to vaporization. For studies of wall regions where melting is expected, the computational cost is fully justified, however for first estimates of the full 3D wall temperature distribution to identify damaged vessel areas, a cheaper simulation tool is needed. Here we propose a new surrogate model that approximates high-fidelity wall damage simulations while preserving essential physical accuracy: FIREWALL (Fast Integrated Runaway Electron WALL loads) [5]. The model relies on a simplified workflow consisting of first interpolating the energy deposition profile from a Geant4 simulations database and then solving a one-dimensional heat equation for the temperature evolution within a wall element. The FIREWALL tool allows for a quick assessment of the danger of incoming RE beams to the wall structures by providing full in-vessel temperature distribution up to the melting point. For example, a typical run for a complete ITER simulation takes a few minutes on a typical computing node. That implies that with FIREWALL many different disruption scenarios can be easily scanned to guide future reactor vessel design studies. [1] S. Ratynskaia et al 2025 Plasma Phys. Control. Fusion (Accepted). https://doi.org/10.1088/1361-6587/ae1c6c [2] M. Hoelzl et al 2021 Nucl. Fusion 61 065001. https://doi.org/10.1088/1741-4326/abf99f [3] Hannes Bergström et al 2024 Plasma Phys. Control. Fusion 66 095001. https://doi.org/10.1088/1361-6587/ad5fb5 [4] S. Ratynskaia et al 2026 Plasma Phys. Control. Fusion 68 025024. https://doi.org/10.1088/1361-6587/ae41e5 [5] VJ. Svensson et al 2026 (In preparation)