Fusion Programme - ENEA - Fusione

3. Technology Programme2007 Progress ReportFig. 3.43 – Back-plate nearly constantradius profile22.5°88 mm128 mmBack-platethe two approaches turnedout to be insignificant from thefluid-dynamic aspect. Thesecond proposal, whichpresents a continuouscurvature change as illustratedin fig. 3.43, seems better. Theproposed fluid-dynamicprofiles are adaptable to boththe European and theJapanese back–plates and willbe extended to the inlet nozzleas well. An important cause ofback-plate damage is theneutron irradiation effect on thestructural material. To betterunderstand the damagedistribution on the component,a neutron damage calculation(fig. 3.44) was performed. It isclear that even if a maximumvalue of 58 dpa/year isreached in the centre of thefootprint, the periphery of thecomponent, where the delicatetightness system is located, isaffected by less than1 dpa/year. This result pavesthe way for the application ofthe bayonet-type back-plate.R482R465Calculationcells345678910369 mmNozzle22.5°55mm356 mm566 mmdpa/yN fluxn/cm 2 s3.10×10 115.22×10 118.40×10 111.09×10 121.05×10 128.29×10 115.01×10 112.80×10 11 1.43×10 -22.43×10 -23.89×10 -25.11×10 -24.95×10 -23.95×10 -22.39×10 -21.31×10 -2 Li flow300 mmy1.3×10 1dpa/y200 mmBeamfootprint58 dpa/yFig. 3.44 - Preliminary calculations of neutron damagedistribution of IFMIF back-platexAn important degrada tion factor of the IFMIF back-plate is represented by theErosion/corrosion erosion/corrosion effect due to the flow of lithium at high velocity (15 to 20 m/s). Inof the target order to experimentally study these effects, the LIFUS III loop (fig. 3.45) wasback-platecommissioned and operated for the first test campaign of 1000 h in 2007. Firstresults at 16 m/s showed there was an enhanced damaging effect with respect tosimple corrosion. The effect of Li velocity on the base-material removal rate appeared very intense for bothAISI 316 and EUROFER 97. A further increase in damage was discovered at the inlet of the corrosionorifice, where the fluid turbulence is higher than in the straight channel. Figure 3.46 shows the increasederosion of the specimen at its inlet side.65