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In this work, thermal ageing of the reduced activation ferritic/martensitic steel CLF-1 with a nitrogen content of 0.025% has been performed at temperatures of 823 K and 873 K for 6000 h. Mechanical properties (hardness, tensile and Charpy impact) and microstructure characterisation has been carried out. After thermal ageing treatments, the steels showed similar values of hardness and tensile properties and a slight deterioration of impact properties were observed. After long term thermal ageing, the M23C6-type precipitation coarsens and agglomerates along lath and grain boundaries. Compared with steels that have lower nitrogen content, the coarsening and agglomeration of M23C6 in the steels with higher nitrogen content is much lower and the steel shows higher microstructural stability. (C) 2013 Elsevier B. V. All rights reserved.

Beryllium and tungsten have been selected as the plasma facing materials of the ITER first wall (FW) and divertor chamber, respectively. China, as a participant in ITER, will share the manufacturing tasks of ITER first-wall mockups with the European Union and Russia. Therefore ITER-grade beryllium has been developed in China and a kind of vacuum hot-pressed (VHP) beryllium, CN-G01, was characterized for both physical, and thermo-mechanical properties and high heat flux performance, which indicated an equivalent performance to U.S. grade S-65C beryllium, a reference grade beryllium of ITER. Consequently CN-G01 beryllium has been accepted as the armor material of ITER-FW blankets. In addition, a modification of tungsten by TiC dispersion strengthening was investigated and a W–TiC alloy with TiC content of 0.1 wt.% has been developed. Both surface hardness and recrystallization measurements indicate its re-crystallization temperature approximately at 1773 K. Deuterium retention and thermal desorption behaviors of pure tungsten and the TiC alloy were also measured by deuterium ion irradiation of 1.7 keV energy to the fluence of 0.5–5 × 10 18 D/cm 2 ; a main desorption peak at around 573 K was found and no significant difference was observed between pure tungsten and the tungsten alloy. Further characterization of the tungsten alloy is in progress.

Tungsten was coated on a W/Cu functionally graded material (FGM) by chemical vapor deposition technique (CVD), and then the tungsten coated tile was brazed on the CuCrZr heat sink with a cooling channel. The thickness of CVD-W was 2 mm deposited by a fast rate of about 0.7 mm/h. The features of the CVD-W coating including morphology, element composition and thermal properties were characterized. A tungsten coating with high density, purity and thermal conductivity is achieved. The bonding strength between the CVD-W layer and FGM was measured using bonding tensile tests. Thermal screening and fatigue tests were performed on the CVD-W mock-ups under fusion relevant conditions using an electron beam device. Experimental results showed that the CVD-W mock-up failed by melting of Cu beneath the tungsten layer under a high heat load of 14.5 MW/m2 and 30 s pulse duration. Thermal fatigue tests showed that the CVD-W mock-up could sustain 1000 cycles at a heat load of 11.7 MW/m2 absorbed power density and 15 s pulse duration without visible failure.

The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwestern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

Vacuum plasma sprayed tungsten coating on graphite and copper substrates has been prepared. VPS-W coated graphite has multilayered silicon and tungsten interface pre-deposited by physical vapor deposition (PVD) and VPS-W coated copper has graded transition interlayer. VPS-W coating was characterized, and then the high heat flux properties of the coating were examined. Experimental results indicated that both VPS-W coated graphite and VPS-W coated copper could endure 1000 cycles without visible failure under a heat flux of approximately 5 MW/m 2 absorbed power density and 5 s pulse duration. A comparison between the present VPS-W coated graphite and VPS-W coated carbon fiber composite (CX-2002U) with Re interface made by Plansee Aktiengesllshaft was carried out. Results show that both Re and Si are suitable as intermediate layer for tungsten coating on carbon substrates.

The hydrogen embrittlement behavior of a V4Cr4Ti alloy (NIFS-Heat 2) has been studied using tensile tests, impact tests and J integral tests. Hydrogen in the alloy was high up to 310 wppm by exposures in a hydrogen atmosphere. The alloy showed different sensitivities to the hydrogen embrittlement in the tests. Hydrogen-induced solid solution hardening occured but caused slight loss in the ductility of the alloy before 215 wppm H in the tensile test. However, the impact toughness, J 1c and the tearing modulus ( T mat ) decreased largely with increasing hydrogen concentration, indicated that the critical hydrogen concentration required to embrittle the alloy might be lower than 130 wppm. The fracture characteristics varied a lot for the different specimens. All these differences were thought being resulted from the stress concentration and the stress assisted hydrogen diffusion in the compact tension specimen and in the necking area of a tensile specimen.

A pulsed electron beam test was used to simulate the thermal response of plasma facing materials under high heat loads during plasma disruptions, particularly for relatively 'long' duration off-normal events such as plasma vertical displacement events. The erosion and erosion products of purified tungsten made by powder metallurgy (PM-W), W and B 4 C plasma sprayed coatings on CFC or copper and C/C composite were investigated. The time evolution of the target current indicates that the erosion products or screening clouds partly or completely shield the incident electron beam, leading to a reduction of the target current and changes in the target current profile. The weight loss of PM-W is smaller than that of the tungsten coating or C/C composite, which is in agreement with the erosion behavior. Erosion products indicate that evaporation is a major erosion mechanism of PM-W, and exfoliation and particle emission are the dominant erosion mechanisms of carbon-based materials and W plasma sprayed coatings.

Experiments were performed using copper electrodes inserted into the wall of a perfectly insulated duct to simulate insulator coating flaking or cracking. The results show that surface electric potential U and MHD pressure drop Δ P exhibit a non-monotonic behavior with increasing V 0 , while the magnetic field B 0 is held constant. Additional experiments were also performed keeping all external experimental conditions fixed while measuring the change of U , V 0 , B 0 , and Δ P with increasing time. It was found that while all external experimental conditions were kept constant, the system changed by itself and U , V 0 and Δ P exhibited a non-monotonic behavior with increasing time. The results seem contrary to the law of Δ P ∝ V 0 B 0 n , but are consistent with conservation of energy, which implies that the change is due to some inherent feature of the system, or possibly instabilities, which may occur due to insulator coating imperfections.

In the last decade, liquid metal (LM) blanket-related key issues, such as the magnetohydrodynamics due to reactor off-normal shutdown, LM velocity two-dimensional effect, manifold three-dimensional effect, insulator coating imperfection effect, and so on, have been investigated in experiments and theoretic analysis in Southwestern Institute of Physics (SWIP). Some results were first observed such as the two-dimensional effect and the instabilities due to insulator coating imperfection in this field. These results also related to the advanced limiter-divertor plasma system. In this paper, we review the progress made by SWIP in this research field.

Several V–Cr–Ti–Al–Si alloys were studied or reviewed of their mechanical properties after their exposure to oxygen, hydrogen and neutron irradiation environments. The results showed that the oxidation kinetic of V4Cr4Ti alloy exhibited parabolic behavior in a flowing argon gas with low partial pressure oxygen over the temperatures from 450 to 600 °C. Most of the alloys showed ductility losses with the increasing oxygen concentration with an exception of V4Ti3Al. Strong sensitivity to hydrogen embrittlement was found for the alloys with the combination of high oxygen concentration and high mechanical strength. It was found that the effect of hydrogen and neutron irradiation on the uniform deformation capability caused by their hardening are equivalent with that of the strain hardening. Fine grain was recommended for the alloys to improve their properties against hydrogen embrittlement and neutron irradiation induced ductility loss.

Standard and Ti- and Nb-modified 316 SS specimens were irradiated with electrons in a high voltage electron microscope (HVEM) up to a dose of 40 dpa at 823 K. Void growth and carbide precipitate processes during irradiation were observed in situ and photographed. The experiment showed that 0.53% Ti-modified 316 SS had good resistance to void swelling, which is due to the small void size and low growth rate. The cold work did not increase the void swelling. In contrast, 0.49% and 0.78% Nb-modified 316 SS showed much higher void swelling than the others studied. However, the cold working of Nb-modified steels suppressed void swelling.