Enhancements in the structural integrity assessment of plasma facing components

Enhancements in the structural integrity assessment of plasma facing components

Enhancements in the structural integrity assessment of plasma facing components 150 150 UKAEA Opendata
UKAEA-CCFE-CP(19)25

Enhancements in the structural integrity assessment of plasma facing components

The preferred design of the ITER divertor target component is the monoblock, comprising a tungsten armour block through which passes a CuCrZr cooling pipe which is joined to the tungsten via a copper interlayer. This construction currently looks to be one of the favoured designs for DEMO. Ideally this structure can be assessed for structural integrity by finite element (FE) analysis using the ITER structural design code for in vessel components (SDC-IC). However, the multiple materials used in monoblock construction introduces a number of factors causing difficulties in the direct application of SDC-IC. The factors include residual stress, dissimilar material joints, the interaction of plasticity in the pipe and interlayer, the effects of irradiation hardening and the possibility of tungsten recrystallization. This presentation discusses some of the FE simulation methodologies that can be employed to overcome these issues as follows. The effects of residual stress (caused be the differential contraction during manufacture) can be factored into the stress assessment by using elasto-plastic methods and the addition of a simulation step representing the manufacturing cycle. The effects of dissimilar joints (which create stress/strain singularities) can be avoided by modified joint design or hot spot methods. The effects irradiation hardening can be simulated directly by applying modified material stress/strain characteristics within an elasto-plastic simulation. The interaction in pipe/interlayer plasticity (which can cause ratcheting) can be catered for by separating material from structural ratcheting and the effects of tungsten recrystallization can be included in analysis by appropriate modification of material characteristics and the assessment of plastic strain above and below the materials DBTT. Using these methodologies, analysis results can be assessed against the current list of SDC-IC failure mechanisms, allowing an improved assessment of structural integrity to be made. These methodologies have been developed to aid the development of a divertor component design analysis procedure for EUROfusion known as the Plastic Analysis Procedure. It is intended that they can be applied in the analysis of all types of multi-material plasma facing components. It is intended that the subject material of this presentation will be published independently of the SOFT proceedings via Fusion Engineering and Design.

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30th Symposium on Fusion Technology (SOFT), Giardini Naxos, Messina, Sicily, 16-21 September 2018
Published date:
05/12/2021