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Fcc pure metals were irradiated with spallation neutrons (energies up to 500 MeV) at room temperature to a neutron fluence of 1 × 1018 n m−2 at KENS, High Energy Accelerator Research Organization (KEK). Defect clusters induced by large collision cascades were examined using transmission electron microscopy (TEM). In Au, large groups of defects included more than 10 clusters, and the damage zone extended over 50 nm, which was larger than that induced by fusion neutron irradiation ( 10 nm) were identified as vacancy type by the conventional inside–outside contrast method. Because of the low neutron fluence, spatial overlapping of collision cascades was ignored. Large vacancy loops are formed through cooperative reactions among subcascades in a single collision cascade with large recoil energy.

In order to improve the performance of vanadium alloys for fusion reactors, yttrium (Y) was added to reduce the interstitial O in the matrix by enhanced precipitation with Y. Effect of Y on interstitial C, N and O, however, remains to be investigated since they affect mechanical and fracture properties for vanadium alloys by pinning dislocations, such as dynamic strain aging (DSA). In this study, tensile tests were carried out on annealed V–4Cr–4Ti and V–4Cr–4Ti–Y alloys from 473 to 1073 K at strain rates ranging from 6.67 × 10−5 to 6.67 × 10−1 s−1 to investigate the performance of DSA. In the case of high-purity alloys, DSA regime was narrowed due to Y addition and the reduction in O content. In the case of O doped V–4Cr–4Ti alloys, DSA regime was also narrowed. This may be because the enhanced Ti–O precipitation reduced the O level in the matrix. Also, coarse precipitates (

Since the decision of blanket redesign by 2007 ITER design review, the blanket system is being developed in the framework of Blanket Integrated Product Team (BIPT) composed mainly of ITER Organizat...

Excellent high-temperature strength and resistance to radiation damage of 9Cr Oxide Dispersion Strengthened (9Cr-ODS) martensitic steel have been realized by nano-size Y–Ti–O complex oxide particles dispersed in the matrix and a dual phase structure consisting of α′-martensite and δ-ferrite. These are produced by mechanically alloying Fe–Cr–Ti powders with Y 2 O 3 followed by a hot-consolidation process. Therefore, the hot-consolidation process is the issue to be clarified for the formation of nano-size oxide particle and δ-ferrite. The temperature dependence of the formation and development of nano-size oxide particles and δ-ferrite using mechanically alloyed 9Cr-ODS raw powder were investigated applying X-ray Diffraction and Small Angle X-ray Scattering measurement at SPring-8 and by Electron Probe Micro Analysis. In situ heating measurement techniques with XRD and SAXS enabled real-time observation of phase transformations and allowed correlation between formation of nano-size oxide particle and δ-ferrite.

To evaluate the applicability of a functionally gradient technique for the fabrication of the armor tile or the interface of the divertor plate element for next fusion machines such as ITER/FER, SiCC and TiCC functionally gradient materials (FGMs) were prepared and tested using an electron and ion beams test facilities. FGM layer with a thickness of 1.0 mm was produced by CVD process on fine grain graphite. Their thermal resistivities were evaluated under a condition for surface heat fluxes up to 70 MW/m2 for durations up to several seconds. As the results, we confirmed that FGMs are clearly better than non-FGMs from a view point of the reduction of thermal stress. Both FGM layers on the graphite bulk material could withstand a temperature difference as high as 1500 K without cracking or melting, leading us to conceive a promising prospect for the application of the divertor plate.

Reduction of interstitial impurities such as nitrogen (N) and oxygen (O) improves the mechanical properties of V-4Cr-4Ti alloys. Yttrium (Y) addition effectively reduces O content by Y2O3 slag-out on the melting ingot surface. The effects of Y addition on mechanical properties were investigated for V-4Cr-4Ti with N ranging from 0.009 to 0.29 mass% and O ranging from 0.009 to 0.36 mass%. The increase in yield stress (YS) and ultimate tensile stress (UTS) for vanadium alloys was saturated above 0.1 mass% in O content, because Ti precipitates increased with increasing O content regardless of Y addition. Y addition had little effect on YS and UTS of V-4Cr-4Ti alloys at room temperature (RT). However, Y addition improved impact properties of alloys highly doped with O. Y addition did not suppress hardening due to O doping but did increase deformation for crack initiation.