Fusion Programme - ENEA - Fusione

Fusion ProgrammeFig. 3.21 - X-ray survey of calibrated sample of the ringFig. 3.22 - Stainless steel ring: mechanical designThe first option analysed is astainless-steel ring designconsisting of two coaxial andinterrupted rings (fig. 3.22).The hoop-force flows fromthe inner ring to the outerand back to the innerthrough a series of verticalkeys. To avoid current loopsthe keys are insulated by a thinalumina film or by interposing athin insulation sheet between thekey and the keyway.Some local stress exceeds what isallowable, but it can be contained by theplastic behaviour of the material. Ring stiffnessand the small elongation due to the lower strain allowedmakes the requirements of assembly accuracy more stringent. Ring machining and assembly are simpleand straightforward. The rolling procedure of the raw material needs specific experience and equipmentthat have not yet been found within the EU, but there might be competent companies in the USA andRussian federation.Fig. 3.23-ITER full-scalering-testing equipment2007 Progress ReportThe second solution is a spiral ring concept based on the possibility of realising a ring by winding on aspool a 3-mm-thick metallic strip insulated by 1 mm of glass fibre. The winding should then beimpregnated following the standard vacuum impregnation techniques already developed for magnetmanufacture. The spiral ring design produces unacceptable stresses in the insulation material and metalsheets, but the problem can be mitigated by[3.11] C. Neri et al. The in-vessel 3D inspection system forITER, Presented at the 22 nd IEEE/NPSS Symposiumon Fusion Engineering (Albuquerque 2007)54