EERA is an official part of the EU SET-Plan. Innovative ferritic-martensitic steels for future Gen IV systems: challenges and JPNM work-programme First ESNII+ Workshop on Joint Programming 22 and 23 October 2015, Brussels. Marta Serrano (CIEMAT)

Contents Introduction Enhanced F/M Oxide dispersion strengthened, ODS Creep Strength Enhanced Ferritic/Martenistic Steels, CSEF Research in SP2 Summary

INTRODUCTION Innovative high temperature resistant steels – Nuclear Fuel cladding tubes 3 Diameter mm, Thickness mm, Several meters long Swelling Creep Coolant RIS Hardening 100 MPa h. Sodium, HLM Up to 750ºC Up to 180 dpa Max 750ºC Up to 180 dpa Max 750ºC

INTRODUCTION: Why F/M steels? Better than Austenitic stainless steels: Swelling resistance - Irradiation Thermal fatigue - lower thermal expansion coefficient (at least 30% lower) and higher thermal conductivity

INTRODUCTION: Improvement of F/M steels To solve the F/M limitations: Low creep strength at high temperature Low temperature radiation embrittlement Oxide dispersion strengthened (ODS) Dispersion of Y-Ti-O nanoparticles Nano-grained microstructure Creep strength enhanced ferritic (CSEF) steels Dispersion of fine MX carbonitrides, Usually VN and Nb (C,N) One of the most effective ways for improving the creep properties is to uniformly distribute fine precipitates with long-term stability at elevated temperatures in the microstructure Irradiation resistance

INTRODUCTION: Improvement of F/M steels To solve the F/M limitations: Low creep strength at high temperature Low temperature radiation embrittlement Oxide dispersion strengthened (ODS) Dispersion of Y-Ti-O nanoparticles Nano-grained microstructure Creep strength enhanced ferritic (CSEF) steels Dispersion of fine MX carbonitrides, Usually VN and Nb (C,N) One of the most effective ways for improving the creep properties is to uniformly distribute fine precipitates with long-term stability at elevated temperatures in the microstructure Irradiation resistance Other limitation to be explored SP1/SP2 Plastic flow localization Cyclic softening Compatibility (coating)

INTRODUCTION: Enhanced F/M Thermo-mechanical treatment Standard HT (tempered at 760ºC) Non-std. HT (tempered at 650ºC) Thermo mechanical treatment

INTRODUCTION: Enhanced F/M Chemical composition – To be optimised for nuclear use Additions of Mn, N, V, Co, B, W… Decrease of C and Nb 9Cr–3W–3Co–0.2V–0.05Nb steels with 0.08C–0.008N–0.014B (MARBN: Martensitic 9Cr steel strengthened by boron and MX nitrides) developed by the National Institute for Materials Science (NIMS)

INTRODUCTION: ODS The good qualities of ODS alloys in terms of resistance to irradiation and high performance at high temperatures result from their characteristic microstructure: homogenously distributed nano- particles in a nano-metric structure

ODS steels ODS cladding tubes are fabricated by powder-metallurgy Anisotropy: texture and grain morphology

Main challenges The main challenges for both ODS & CSEF at different levels, among others: “Innovative “ First ODS patent 1974 CSEF in the fossil industry for decades Production: Cost Reproducibility Industrial supplier Fabrication Welding Inspections Irradiation Thermal stability A complete knowledge of deformation mechanisms, microstructure stability, and more scientific issues &

EERA JPNM SP2 Research within SP2 is focused on enhance swelling and creep resistance of candidate metallic materials for long term Gen IV prototypes and reactors Participants – Total effort 50 py/y 16 Members: CEA, CIEMAT, CNR, CNRS, CVR, ENEA, HZDR, JRC-IET, KIT, KTH, NCBJ, NRG, PSI, SCK-CEN, UKERC, VTT, 7 Associates: Aalto Univ., CSM, EDF, MPA, NNL, RATEN, STUBA : Focus on ODS activities partially funded by EU FP7 GETMAT ( ), MATTER ( ), MATISSE ( )

Research in SP2 ( ) Monitoring national programmes European activities on ODS/Enhanced creep alloys “Catalogue” of European ODS heats ODS fabrication, characterization and welding (FP7/GETMAT) Extruded bar and plates Tensile, Charpy, Fracture toughness, LCF, Small punch, creep. Explosive, FSW, EMPT and conventional TIG/EB joining techniques Irradiation campaign

Research in SP2 ( ) Exploring ODS new fabrication routes: (FP7/MATTER) Improvement of powder metallurgical process and optimization of final thermo- mechanical treatment Conventional steel making techniques (introducing the oxide particles in the melt) Spark plasma sintering techniques ODS cladding tubes characterization (FP7/MATISSE, FP7/GETMAT follow-up) Microstructural stability under high temperature and irradiation Anisotropy studies (biaxial mechanical testing) Screening activities under accidental scenario SPS - CEA MATISSE Cladding tubes (EDF) SPS-HZDR Low energy milling CSM MATISSE Cladding tubes Small punch CIEMAT

Next period ODS: Improvement of production routes Deep analysis of deformation mechanisms (brittle and high temperature) and fracture Stability of the microstructure under long term exposure at high temperature and irradiation, including recrystallization (abnormal grain growth) studies Creep-Strength-Enhanced F/M steel: Optimization of microstructure and treatments to balance the improvement of creep and minimal loss of toughness Microstructure stability under deformation, high temperature and irradiation Compatibility Alumina forming Alloys EERA JPNM Pilot Projects Proposal AFROS FRACTO (SP1-SP2) PROMETEUS CREMAR ALCORE (SP1-SP2)

Research in SP2 16 GETMAT ( ) (~1.5 M€ / 50%) ODS fabrication & characterisation MATTER ( ) (~0.5 M€ / 50%) Optim. fabrication route MAtISSE ( ) (~450 k€ / 50% k€ in-kind) Clad. tube characterisation EERA JPNM Pilot Projects ( ) FRACTO: Fracture toughness (SP1_SP2) ALCORE: Alumina forming steels (SP1_SP2) CREMAR: Creep Strength Enhanced Ferritic (CSEF) AFROS: Alternative ODS production routes PROMETEUS: Micro-plasticity EERA PPs ( ) (~5.6 M€)

Summary Research within SP2 is focused on enhance swelling and creep resistance of candidate metallic materials for long term Gen IV prototypes and reactors ODS alloys Enhanced F/M steels Alumina forming Alloys No activities on Ni-based alloys R&D partially funded by EURATOM FP7 (GETMAT, MATTER, MATISSE) Pilot Projects proposals for the next period ( ) Fracture behavior (ODS, F/M) – Small specimens & Industrial partners Radiation resistance (ODS) –Ion irradiation inc. He/H New fabrication routes for ODS – High Temperature & Industrial partners Creep-enhanced F/M steels – High Temperature & Industrial partners Alumina forming alloys – Pb Compatibility & Industrial partners

Thank you for your attention