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China Low Activation Martensitic (CLAM) steel as one of 9%Cr ferritic-martensitic steels was designed as the structural materials for fusion reactors and lead-based Reactor in China. The long-term thermal stability of precipitated phases in CLAM steel at 550 °C was systematically studied in this paper, including coarsening kinetics, number density and shape stability. Based on large data statistics, the coarsening kinetics of M 23 C 6 carbide, MX carbonitride and Laves phase were analyzed to develop a coarsening model of each precipitated phase, respectively. The results showed that the coarsening rate of Laves phase was about 100 times than that of M 23 C 6 carbide after aging for 20,000 h at 550 °C. The number density of precipitated phases increased firstly and then decreased with increasing of aging time due to a dynamic equilibrium process of the precipitation and dissolution of precipitated phase. The results will help to deep understand degradation mechanisms after thermal aging. [ABSTRACT FROM AUTHOR]

Reduced-activation ferritic-martensitic (RAFM) steel is considered as the primary candidate structural material for blankets of ITER, CFETR and DEMO. Several RAFMs have been developed in China (CN-RAFMs) such as CLAM, CLF-1, modified RAFMs and oxide dispersion strengthened RAFMs (ODS-RAFMs). The mechanical properties, irradiation behaviors, additive manufacturing and joining technologies of structural materials have been comprehensively studied. Qualifications of CN-RAFMs are on-going for ITER-TBM fabrication, with emphasis on material property databases and standardization. A new neutron irradiation program is being carried out for a series of fusion materials e.g. RAFMs and ODS-RAFMs with doses up to 40 dpa. Joining technologies (e.g. electron beam welding, tungsten inert gas welding, laser beam welding and diffusion welding, etc.) and advanced additive manufacturing are performed to overcome the big challenges of the blanket fabrication before ITER, CFETR and DEMO. The databases and standards for CLAM and CLF-1 were established respectively, and the specification and qualification of them are underway for ITER-TBM. In this paper, the latest development and strategy on fusion energy in China are briefly introduced, and the progresses of R&D activities on CN-RAFMs aiming for the engineering applications are reviewed. [ABSTRACT FROM AUTHOR]

China Low Activation Martensitic (CLAM) steel is selected as the candidate structural material in Fusion Design Study (FDS) series fusion reactor conceptual designs. The creep property of CLAM steel has been studied in this paper. Creep tests have been carried out at 823 K and 873 K over a stress range of 150–230 MPa. The creep curves showed three creep regimes, primary creep, steady-state creep and tertiary creep. The relationship between minimum creep rate ( ε ̇ min ) and the applied stress ( σ ) could be described by Norton power law, and the stress exponent n was decreased with the increase of the creep temperature. The creep mechanism was analyzed with the fractographes of the rupture specimens which were examined by scanning electron microscopy (SEM). The coarsening of precipitates observed with transmission electron microscope (TEM) indicated the microstructural degradation after creep test. [ABSTRACT FROM AUTHOR]

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe 2 Al 5 layer was formed on CLAM substrate by pack cementation process with Fe 2 Al 5 donor powder and NH 4 Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe 2 Al 5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe 2 Al 5 as a function of processing parameters. The Wagner’s equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al. [ABSTRACT FROM AUTHOR]

Abstract: The liquid metal and solid ceramic pebble breeder blankets have become the most promising blankets for ITER-TBMs or DEMO reactors in China and the world due to their potential advantages. In recent years the corresponding research work on fusion reactor materials mainly focuses on structural materials, plasma facing materials and the functional materials for the blanket such as breeder, coating and flow channel insert etc. for the successful application of fusion energy in the near future. The R&D on those materials in the two kinds of blankets is being carried out widely in China, including fabrication and manufacturing techniques, physical/mechanical properties assessment before and after irradiation, joining techniques for structural materials, compatibility evaluation, and the development and verification of the criteria for fusion material designs. The progress on main R&D activities of fusion reactor materials in China is introduced and prospected in the paper. [Copyright &y& Elsevier]

Abstract: A series of fusion reactors (named FDS series) have been designed and assessed in China, with four types of liquid lithium lead blankets including the RAFM steel-structured He-cooled quasi-static LiPb tritium breeder (SLL) blanket, the RAFM steel-structured He–LiPb dual-cooled (DLL) blanket, the RAFM steel-structured refractory material thermally-insulated high temperature LiPb (HTL) hydrogen production blanket and the RAFM steel or optionally the austenitic stainless steel-structured He–LiPb dual-cooled high level waste transmutation (DWT) blanket. To demonstrate and validate the feasibility of the candidate blankets for fusion energy application, the three-phases-strategy of TBM (test blanket module) development, i.e. material R&D and out-of-pile experimental mockup, EAST-TBM and ITER-TBM have been proposed. A brief overview of the four types of LiPb blanket designs and their goals are given. Material technology requirement and development strategy are also presented in this paper. [Copyright &y& Elsevier]

Abstract: In this paper, we report some new progress on plasma facing materials in University of Science and Technology Beijing (USTB), China. They include fabrication of tungsten coating with ultra-fine grain size by atmosphere plasma spraying; fabrication of tungsten with ultra-fine grain size by a newly developed method named as resistance sintering under ultra-high pressure; using the concept of functionally graded materials to join tungsten to copper based heat sink; joining silicon doped carbon to copper by brazing using a Ti based amorphous filler and direct casting. [Copyright &y& Elsevier]

Thermal aging experiment is an effective method to evaluate the thermostability of structure materials which serve in high temperatures. But it difficult to acquire the aging data throughout service term, because it would take a long time. Hence, an accelerating thermal aging model of China low activation martensitic (CLAM) steel was built in this paper to shorten the time of the thermal aging experiment. The microstructure analysis and Charpy impact tests were conducted on CLAM steel after thermal aging with different temperatures. The results showed that raising temperature could accelerate the grain coarsening process and the main factor of ductile-to-brittle transition temperature (DBTT) increasing was grain coarsening after aging for less than 8000 h which were analyzed by fracture model. Hence, the activation energy of grain coarsening with a value of 47.4 kJ/mol could be regarded as the activation energy of thermal aging. Then a model of accelerating thermal aging was built by using Arrhenius formula to evaluate the properties degradation during thermal aging. This strategy could be used to accelerate thermal aging process of CLAM steel through raising aging temperature and it could save time and cost for aging experiment. [ABSTRACT FROM AUTHOR]

Abstract: Research and development (R&D) on fusion nuclear technologies in China are reviewed in this paper. Our objective is to present the main achievements and key issues regarding plasma facing materials (PFMs) and plasma facing components (PFCs) in China in the past 2years, which include the properties of doped-tungsten powders obtained via wet chemical method, mechanical alloying (MA), and sintered pure and doped-tungsten by spark plasma sintering (SPS), resistance sintering under ultra high pressure (RSUHP). Results show that the superfine powders of W-La2O3 and W-TiC prepared by wet chemical method have more uniform size and good dispersion than MA. And the fabricated W-TiC powders had particle sizes ranging from 50 to 1000nm. In addition, two sintering methods of SPS and RSUHP are investigated to fabricate tungsten blocks with high densities. We also discuss the effect of rolling and swaging on the crystal size and mechanical properties of tungsten. For PFCs, joining of tungsten to copper was conducted by low pressure plasma spray (LPPS), air plasma spray (APS), cold spray, chemical vapor deposition (CVD), and electro-deposition from molten salt, in which the maximum thickness of tungsten coatings by electro-deposition was 1255μm with no voids and cracks. [Copyright &y& Elsevier]

Abstract: Several types of reduced activation ferritic/martensitic (RAFM) steel have been developed over the past 30years in China, Europe, India, Japan, Russia and the USA for application in ITER test blanket modules (TBMs) and future fusion DEMO and power reactors. The progress has been particularly important during the past few years with evaluation of mechanical properties of these steels before and after irradiation and in contact with different cooling media. This paper presents recent RAFM steel results obtained in ITER partner countries in relation to different TBM and DEMO options. [Copyright &y& Elsevier]