Fuel retention in plasma facing materials of the JET ITER-like wall

This thesis, presents results from the Joint European Torus (JET), beryllium ITER-like wall. Isotopic hydrogen retention is investigated at three microstructurally unique sites: erosion zones, co-deposition zones, and melted material, found across the reactor at the inner and outer wall limiters and dump plate tiles. The techniques applied to these novel inservice materials were: Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX), Raman Spectroscopy; Focused Ion Beam (FIB) 3D milling; Scanning Transmission Electron Microscopy (STEM) with Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive X-Ray (EDX); Atom Probe Tomography and Thermal Desorption Spectroscopy (TDS). Clustering of deuterium (D) with beryllium deuteride (BeD2) was found at the outer eroded material, whilst not at the inner. BeD2 was present at the core of D clusters up to 8 at%. Co-deposition at the outer limiter tile was governed by beryllium oxide (BeO), whilst at the inner it was governed by Be with D. EUROFusion samples produced from High Power Impulse Magnetron Sputtering (HiPIMS) returned similar EELS results to JET samples; presenting a reasonable model. Melted material produced highly oxidised zones devoid of metallic impurities from marker layers in spatially optimum sites, surrounded by grains produced via high temperature material mixing. Several types of beryllium deuteroxide (BeOD) with varying stoichiometries were presented Retention is lowest at the inner wall eroded zone, increasing at the outer wall eroded zone, and increasing further between inner to outer wall codeposits. Melted material, remains an outlier. Overall total retention, in melted materials was similar to outer wall co-deposit, however composed of over 77% H. Material mixing was suggested the cause due to beryllium/nickel alloying seen in melted materials.