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«  IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM  »

«  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

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«  IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM  »

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  1. « 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 inducestrong modifications on the microstructure, chemical composition, atomic and crystallographic structure • with resulting :Significant Hardening and Embrittlement • Possible loss of dimensional stability • ·Critical issues : thestructural 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 PROGRAMME : « IRRADIATION EFFECTS IN MARTENSITIC STEELS UNDER NEUTRON AND PROTON MIXED SPECTRUM » 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 2002. PIE will start on beginning 2003. Experiments in HFR and BR2 are in progress. STIP I and STIP II irradiations in SINQ are finished. PIE in progress.

  3. 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 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 theJülich compact cyclotron. • Implantation temperatures (Timpl) used: 150-550°C. • He content: 600-5000 appm. • Materials: 9Cr1Mo (EM10) and 9Cr1MoVNb(T91) steels. • He effects on tensile properties are strongly dependant on the implantation temperature. • For Timpl = 250°C => Very important hardening, Dsy > 500MPa (for 5000 He appm), • Complete loss of ductility for He ≥ 2500appm. • 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 Timpl > 250°C => Ductility loss is much less pronounced. 5000 He appm Ttest =25°C Total elongation versus He content Brittle intergranular fracture mode From J. Henry, P. Jung, IWSMT-5, Charleston, SC, USA, May 2002

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