Present fluid based 3D models for describing runaway electrons (REs), e.g. in M3D-C1 and JOREK, capture the mutual interaction of the REs onto the MHD modes, but do not resolve the RE phase space dynamics, orbit shifts and the transport in stochastic fields accurately. For this reason, a hybrid fluid-kinetic model in JOREK[^1] describes the REs with a full-f relativistic particle in cell (PiC) approach using either full-orbit[^2] or drift kinetic RE descriptions[^3]. Previously, the 3D kinetic avalanche source was implemented for this model consisting of a relativistic large-angle collision operator along with periodic resampling of the markers to limit their number even though the number of REs grows exponentially. This implementation was benchmarked[^4] against analytical expressions from literature[^5] and good agreement was found when applying the same cut-off momentum for the large-angle collisions. In continuation of this work, a first physically relevant 3D application is presently progressing by simulating an RE beam termination scenario in JET with the large-angle collision operator switched on such that a direct comparison to results without the collision operator are possible. At this stage, simulations are extremely expensive, making it challenging to cross even the comparably short time scale of the termination event. Future optimizations and GPU porting will therefore be needed. As simulations can cross large time scales during which the flux surfaces are nearly intact, a lower dimensional treatment in space is being considered to reduce the computational costs where possible. Additional work is currently invested in improving the resampling algorithm to ensure accurate momentum and energy conservation. Further work will account for collisions with bound electrons and the implementation of the primary nuclear sources. [^1]: [M. Hoelzl, G. T. Huijsmans, S. J. Pamela et al.](https://iopscience.iop.org/article/10.1088/1741-4326/abf99f/meta), Nuclear Fusion, vol. 61, no. 6, 2021 [^2]: [Hannes Bergström, Shi-Jie Liu, Vinodh Bandaru et al.](https://iopscience.iop.org/article/10.1088/1361-6587/adaee7), Plasma Physics and Controlled Fusion, vol. 67, no. 3, 2025 [^3]: Shi-Jie, Liu, [contribution at this meeting](https://ft.nephy.chalmers.se/?p=abstract&id=180) [^4]: F. Wouters, [Master thesis](https://research.tue.nl/en/studentTheses/implementation-and-validation-of-the-avalanche-source-for-a-3d-ki), 2024 [^5]: [P. Aleynikov and B. N. Breizman](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.155001), Physical Review Letters, vol. 114, no. 15, 2015