Composites Roadmap – Structure and Priorities (A8.1)

This project has received funding from the Euratom Research and Training Programme under Grant Agreement No. 101165375 Maxime ZABIEGO (CEA-France) –CONNECT-NM’s sub-task 6.4.5.1 leader CEN WS064 PG2 Technical Meeting n°10 –October 23-24, 2025 Composites Roadmap –Structure and Priorities (A8.1) Table of contents •Context & Objectives •Introduction •French Programme •Existing codes & standards •Key features •Applications •French Programme •Key challenges & Technology gaps •Feedback & Philosophy •Damage versus failure •Experimental versus numerical proof •Roadmap for qualification & codification •Components: materials & structures •Characterization & modelling •Design criteria & rules •Conclusion October 24th 2025 CEN WS064 PG2 meeting 1 Context & objectives October 24th 2025 CEN WS064 PG2 meeting Context & Objectives PG2 activity to include Composites in Design Codes •December 2023 meeting: Jacobs, ASME Section III – Division 5 –Graphite in HTR Cores •December 2023 meeting: Thorizon, Composites & Ceramics in Design Codes •October 2024 meeting: NAAREA, Design approach for SiC components •April 2025 meeting: CEA/Framatome,CONNECT-NM task 6.4.5.1 –Roadmap proposal for establishing design rules for ceramic fiber composites Proposal for a White Paper on composites & ceramics in Design Codes (PG2 Action 8.1) Structure proposed by K.F. Nilsson (email, May 25th 2025) for discussion at the June 6th 2025 PG2 meeting Review related activity in the French Programme (cannot ignore ATF activity in the US and, recently, in China, though: 2025 showed major increase in publications) 2 Introduction October 24th 2025 CEN WS064 PG2 meeting Introduction : French Programme CEA research on CMCs (mostly SiCf/SiC) for core components (fuel clad & SA-duct) over the last 20 years :GFR (2005-2012) &ATF for PWRs (Ongoing since 2012, for/with Framatome) •Design,fabrication,characterization &modelling of fuel clad & SA-duct (mixed CMC-metal) for GFR studies •Tentative work to adapt the Ramses-II / RCC-MRx code to CMC clad & SA-duct for GFR → See Cécile Pétesch •Design,fabrication,characterization,modelling &irradiation of fuel clad (mixed CMC-metal) for PWR-ATF studies, for/with Framatome •Normative activity on CMC characterization:NF EN ISO 20323,21971 & DIS 4255 •CONNECT-NM subtask 6.4.5 on codification,modelling &characterization of fuel clad (mixed CMC-metal) for PWR-ATF studies, with Framatome The present core product is the mixed CMC-Metal (alternative to full-ceramic) cladding for ATF in PWRs Patent WO 2011/042406 (A1) Patent WO 2013/017621 (A1) Patent WO 2025/083082 (A1) October 24th 2025 CEN WS064 PG2 meeting Introduction : existing codes & standards •Codes ➢The reference code for PWR fuel elements (Zr-based clad) is RCC-C…but it does not discuss design criteria & rules →Potential interest in the INL approach for SiC claddings & NUREG-2246 (derived from NUREG-0800 - Section 4.2) ? ➢The reference code for design criteria & rules could be RCC-MRx…but it appears complex to adapt to CMCs ➢The ASME BPVC.III.5 code specifically addresses composite (CMC) structures, with asemi-probabilistic approach that could apply to SiCf/SiC claddings…provided that probabilistic approaches can be accepted by European Safety Authorities •Standards ➢Ongoing work on standards pertaining to mechanical characterization of CMC tubes October 24th 2025 CEN WS064 PG2 meeting Introduction : Key features •CMC-based components rely on astructure rather than on amaterial: component dependence is stronger than for metal-based components →fiber / interphase / matrix selection,fibrous architecture,densification process,surface protection…CMCs are intrinsically characterized by orthotropic behaviours imposed by their architecture •Sensitivity to cracking damage: preserves some mechanical strength but raises performance / safety issues regarding leak-tightness,corrosion,thermal conductivity… •Behaviour: ➢Probabilistic vs deterministic quasi-deterministic pseudo-ductile behaviour, with sensitivity to defects controlled by design options ➢Differential evolution in case of materials combination (e.g., mixed CMC-Metal clad), importance of secondary stress &limited acceptable strain •Graceful failure mode preserving component geometry (e.g., prevent ballooning in LOCA scenario limited impact on neighbouring structures / environment), but moderate-to-low toughness and reduction of the resisting section with progressive load transfer to fibers •Resistance to HT scenarios & irradiation (no strengthening &no “ductility” loss): improved performance is acknowledged but somewhat lacks discussion of practical operational limit •Joining:potentially complex issue, with many options but seemingly little consideration for standardized testing allowing to compare them 3 Applications October 24th 2025 CEN WS064 PG2 meeting Roadmap for qualification & codification : French Programme Components: Materials & Structures Identification of relevant structures (application-related components) Identification of relevant constituents: fiber, interphase, architecture & densification “Material”appendix / data sheet: One for each structure !!! Cannot ignore structure effect & implementation for each constituent (fiber, interphase & matrix) would impose likely prohibitive multiscale modelling October 24th 2025 CEN WS064 PG2 meeting Roadmap for qualification & codification : French Programme Characterization and modelling Normative activity to define characterization protocols used for “Material”Appendix Modelling activity to define simulation protocols:macroscopic versus multiscale Non-linear elastic behaviour October 24th 2025 CEN WS064 PG2 meeting Roadmap for qualification & codification : French Programme Design criteria & rules Appear to depend on the considered application, through the notion of acceptable damage (e.g., cracking versus leak-tightness with or without liner) relative to specified functional requirement Amethod of analysis must be identified: experimental and/or numerical (SCT) •Presently, the maturity of SCTs appears too low for fuel cladding simulation •Experimental analysis partly benefits from the fact that SiCf/SiC moderately depends on temperature & irradiation…but not entirely (swelling) Criteria & rules must be defined / justified according to the selected method, which might be easier through ASME’s semi-probabilistic approach (PoF) than with a deterministic one 6 Conclusion & perspectives October 24th 2025 CEN WS064 PG2 meeting Conclusion & perspectives The priority, I think, is to honestly clarify whether there is atrue interest in pursuing the development of CMC components for nuclear use in Europe If this interest exists, an involvement in codification activities is an option,but it would require some degree of open communication on the relevant applications It is not clear to me whether this can be conducted in aunified approach,or whether it will need to account for application specificities (component functional requirements, environments / scenarios…) As regards PWR ATF claddings, the diversity of options clearly lacks the normative framework necessary to compare them on many aspects •Qualification (characterization / testing protocols) is progressively improved by normative activities •Design criteria / rules appear to be a much “wilder” field of investigation, which might require a pragmatic approach:start from RCC-C to clarify requirements and their relationship to damage / failure ? A stepping stone might be offered by exploring the possibility of extending the “Guide for introducing a new material in the RCC-MRx –ACEN/RX.17.006 revA”to CMC structures Thank you! This project has received funding from the Euratom Research and Training Programme under Grant Agreement No. 101165375 [email protected] Who wants to ask the first question ? ☺ 7 Complementary slides October 24th 2025 CEN WS064 PG2 meeting A composite is not a material, it is a (complex) structure Fiber (SiC) +interphase (PyC) +matrix (SiC) +architecture (FW) +densification (CVI) Architecture = type (FW, 2D-W, 3D-B…), fiber fraction, number of layers, angle… Filamentary Winding 2D-Weaving 3D-Braiding April 14th 2025 CEN WS064 PG2 meeting Mechanical behaviour of composites Modelling of damageable behaviour The mechanical response of composites to loading (imposed stress and/or deformation) leads to progressive damage: cracking initiation / propagation / saturation & failure Abrupt change in mechanical response Matrix cracking saturation B C BC A A (PLS) D (UTS) PLS (matrix cracking initiation) UTS (mechanical failure) D A April 14th 2025 CEN WS064 PG2 meeting Experience from previous studies Fully-ceramic cladding : Thermomechanical feedback Mechanical (T-induced loads) & thermal response influence one another Behaviour specific to CMC materials must be specifically addressed L. Duquesne et al., Top Fuel 2018