Finite element analysis (FEA) is widely used in engineering to accurately model physical systems. FEA enables multi-physics investigations to be undertaken efficiently and increases the cohesiveness of interdisciplinary engineering assessments. Thanks to the recent implementation of the FEA Unstructured Mesh capability (UM) into MCNP6, radiation transport is now able to contribute more effectively to such multi-physics investigations. Furthermore, the use of UM in MCNP allows complicated components to be modelled more accurately since it does not have the geometrical limitations of the alternate Constructive Solid Geometry method (CSG), leading to more accurate simulations and inherent results. The ITER Electron Cyclotron-Upper Launcher (EC-UL) M3 Mirror is a complex component currently under design that had required various engineering assessments that utilise FEA such as mechanical and thermohydraulic. Therefore, this neutronics assessment took advantage of the UM capability of MCNP6.2 to be consistent with the other assessments. The peak volumetric nuclear heating for this component was found to be 3.76 ± 22.0% W/cm3 by this method. The total integral nuclear heating was found to be 6595.1 ± 0.6 W, an increase of 9.3% on the previous design but with a slightly different deposition distribution. Crucially, the total integral nuclear heating of the CuCrZr reflector was determined to be 142.92 ± 0.07 W, a decrease of 69% from the previous mirror design allowing the fulfilment of the mechanical code and standards.