1 SPIRE Project coordinated by CEA – Contractors : CEA, CIEMAT, CNRS, NRG, ENEA, PSI, KTH, SCK/CEN, FZK « IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM » ACRONYM : SPIRE BACKGROUND AND PROBLEM  The spallation target structures and the beam window are expected to undergo severe and specific irradiation damage in an ADS environment due to:Displacement per atom (dpa) Spallation elements production (He, H, P, S, Ti, Ca,…)  Irradiation effects induce strong modifications on the microstructure, chemical composition, atomic and crystallographic structure with resulting :Significant Hardening and Embrittlement Possible loss of dimensional stability  Critical issues : the structural integrity and the life-time of the target structures and the beam window First concern : Brittle Fracture 9-12%Cr martensitic steels appeared as the best candidates to resist these irradiation conditions. Several alloys selected: Conventional martensitic steels : 9Cr-1Mo (EM10), 9Cr-1MoVNb (T91) and 12Cr1MoWV (HT9) Experimental alternative steels : 7-9Cr 1-2W V Ta OBJECTIVES OF SPIRE PROJECT in the perspective of an ADS transmutation Demonstrator  Determine relevant properties (tensile, impact, fracture toughness, irradiation creep) of the selected structural steels under irradiation conditions simulating the spallation environment.  Provide the basic mechanisms and modelling for the observed phenomena  Contribute to specify a reference material and give paths for the development of advanced window materials  Provide basic data and guidance for conceptual design purposes

2 SPIRE Project coordinated by CEA – Contractors : CEA, CIEMAT, CNRS, NRG, ENEA, PSI, KTH, SCK/CEN, FZK SPIRE PROGRAMME : « IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM » METALLURGY BEFORE IRRADIATION -Additional characterisation of the selected steels -Specif. and fabrication of steels doped with spallation elements (P, S, Ti) -Physical metallurgy of doped steels NEUTRON IRRADIATION AND POST-IRRADIATION TESTS -BOR60 : Altair experiment, Ti=325°C, 40 dpa max -HFR : Ti=250°C, ~3 dpa, « tailored He production » -BR2: Ti=200°C, 6 dpa max EXPERIMENTAL SIMULATION OF IRRADIATION EFFECTS IN SPALLATION SPECTRUM -Effect of He on tensile properties & microstructure -Effect of Ti, Ca, H on microstructure and hardening -Chemical analysis of clusters and precipitates (3D tomographic atom probe) IRRADIATION UNDER NEUTRON AND PROTON MIXED SPECTRUM AND POST-IRRADIATION TESTS Irradiations performed in SINQ facility: - STIP I (protons: 575MeV), Ti= °C, 12dpa max - STIP II (protons: 575MeV), Ti= °C, 22dpa max NUMERICAL SIMULATION AT ATOM SCALE -Irradiation damage characterisation of the beam window and target structures -Modelling of obstacle forces due to irradiation defects and of associated hardening -Cohesion energy computation of segregated interfaces based on electronic structure -Simulation of defects production and migration rates in FeCr alloys WORKPACKAGE CONTENTS - MAIN OUTPUTS EXPECTED FROM SPIRE SPIRE programme is carried out according to the initial schedule. In particular : The irradiation experiment in BOR60 finished on October PIE will start on beginning Experiments in HFR and BR2 are in progress. STIP I and STIP II irradiations in SINQ are finished. PIE in progress.

3 SPIRE Project coordinated by CEA – Contractors : CEA, CIEMAT, CNRS, NRG, ENEA, PSI, KTH, SCK/CEN, FZK SPIRE PROGRAMME : « IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM » MAIN OUTCOMES Irradiation under neutron and proton mixed spectrum at SINQ (PSI) - The magnitude of hardening and the associated loss of ductility, determined from tensile tests, increases with decreasing irradiation temperature for Ti ≤ 300°C. At Ti = 350°C, a higher ductility is obtained compared to values measured at Ti=300°C, even though the dose and the He-content induced by irradiation are higher. The ductile-brittle transition temperature (DBTT) was determined from small punch tests on 3mm diameter discs for 9Cr1MoVNb (T91) and 9Cr2WTaV(F82H) steels. - An important increase of the DBTT is obtained with the dose for irradiation temperatures Ti ≤ 300°C. It must be noted that the increasing dose is associated to an increasing irradiation temperature and an increasing content of He, which ranges from about 200 He appm (for about 2.5 dpa) up to 600 He-appm for the higher doses. From Y. DAI, IWSMT-5, Charleston, SC, USA, May 2002

4 SPIRE Project coordinated by CEA – Contractors : CEA, CIEMAT, CNRS, NRG, ENEA, PSI, KTH, SCK/CEN, FZK SPIRE PROGRAMME : « IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM » MAIN OUTCOMES (continuation) Experimental simulation of irradiation effects in a spallation spectrum (CEA, FzJ) Helium implantation experiments were performed using the Jülich compact cyclotron. Implantation temperatures (T impl ) used: °C. He content: appm. Materials: 9Cr1Mo (EM10) and 9Cr1MoVNb(T91) steels. He effects on tensile properties are strongly dependant on the implantation temperature. For T impl = 250°C => Very important hardening,  y > 500MPa (for 5000 He appm), -Complete loss of ductility for He ≥ 2500 appm. -Intergranular fracture mode Proposed mechanisms: Yield stress increase is due to a high density of small He bubbles. The intergranular fracture is related to the intragranular hardening and the loss of cohesion energy of grain boundaries in presence of helium. For T impl > 250°C => Ductility loss is much less pronounced. Ttest =25°C Brittle intergranular fracture mode 5000 He appm Total elongation versus He content From J. Henry, P. Jung, IWSMT-5, Charleston, SC, USA, May 2002