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To improve tritium permeation resistance and toughness of Al2O3 coating, a new graphene oxide (GO)-alumina (Al2O3) composite coating as tritium permeation barrier was designed in this paper. GO was added into Al2O3 to prepare the composite coating of GO-Al2O3 by a sol-gel method. The results showed that the deuterium permeation reduction factor (PRF) of 0.5 wt% GO-Al2O3 coating was higher than that of the pure Al2O3 coating at 500 ℃. It was related to the GO nanosheets blocking the diffusion of deuterium atoms in the Al2O3 coating and reducing the permeability. Meanwhile, the toughness of the 0.5 wt% GO-Al2O3 coating was enhanced by about 40 % than the pure Al2O3 coating. The reason can be speculated that GO nanosheets can prevent the cracks propagation in the composite coating of GO-Al2O3. This study could provide a new material of tritium permeation barrier for fusion reactors.

This paper highlights the results of a study on the high cycle fatigue strength and fracture mechanism of China Low Activation Martensitic (CLAM) steel. The high cycle fatigue test results showed that the fatigue strength of CLAM steel decreased with the temperature, and the condition fatigue strengths ( N = 10 7 ) were 275 MPa and 235 MPa at 723 K and 823 K, respectively. The fractograph results indicated that the fractures were mainly initiated from the surface of the specimen.

Dissimilar welding between China low activation martensitic (CLAM) steel and 316L austenitic stainless steel was investigated to achieve the reliable connection between test blanket modules (TBMs) and piping system in the international thermonuclear experimental reactor (ITER). The dissimilar joints were welded by tungsten inert gas (TIG) welding process with a filler material type-309. In order to stabilize the microstructure and improve the strength and toughness, post-weld heat treatments (PWHTs) of tempering at 740 °C, 780 °C and 820 °C, respectively, for 2 h were performed. The microstructure observation showed that tempering at 740 °C for 2 h was the preferable PWHT rule in this work. After the treatment, the hardening in heat affected zone (HAZ) on the CLAM steel side decreased remarkably. The tensile strength of the joint was roughly the same as that of the base metal. The impact toughness of HAZ on the CLAM steel side was 77% of that of the base metal. The absorbed energy of HAZ of 316L steel decreased by 93 J, and that of weld metal (WM) was 110 J after the treatment.

The dual functional lithium lead blanket is chosen as one of the candidate blankets for China fusion reactor, for its advantages of tritium breeding and good heat exchange performance. As one of the most important components of the blanket, the first wall (FW) is assembled with China low activation martensitic (CLAM) rectangular tubes and plates by hot isostatic pressing (HIP)–diffusion bonding (DB). In this work, the rectangular tube fabrication and FW assembly were carried out in order to verify the feasibility of the FW fabrication scheme. The mechanical property and dimensional accuracy of CLAM rectangular tubes were tested, the microstructure observation and non-destructive detection revealed the sound of the FW mock-up, and the reliability of the FW mock-ups is under evaluation.

The low cycle fatigue (LCF) property of welded joint is a key issue of fusion reactor blanket safety. In this study, LCF behavior of China low activation martensitic (CLAM) steel joint welded by electron beam was investigated under different strain amplitudes. The experimental results showed that the LCF life of the welded joint was lower than that of the base metal. Both the base metal and the welded joints exhibited continuous cyclic softening. However, the welded joint revealed a lower cyclic peak stress compared to that of the base metal. The welded joint failed in the welded zone at the strain amplitude of 0.3% and failed in the base metal at the strain amplitudes of 0.5%, 0.7% and 1.0%, respectively. The welding inclusion or defect in the surface could be the source of fatigue crack and the fatigue crack propagated in welded metal and heat affected zone with a transgranular fracture mode.

The microstructure of China Low Activation Martensitic steel (CLAM) and its influence on mechanical properties were investigated. The tensile test showed that the strength of CLAM (HEAT 0603A) was higher than that of HEAT 0408B at room temperature, and the reverse results were obtained at elevated temperatures. The results indicated that the microstructure was composed of dispersived carbide particles and lath martensite with high dislocation density. The main precipitation phases were Cr-rich M 23 C 6 carbides precipitated mainly along the lath boundaries and prior-austenite grain boundaries and Ta-rich MX particles precipitated mainly in the laths and lath boundaries. The finer lath was the main reason for the higher strength of HEAT 0603A compared with HEAT 0408B at room temperature; contrasted with the lower strength at high temperature. Heavier hot forging deformation degree was considered as the main possible reason for the decrease of martensite lath width in HEAT 0603A.

The first wall (FW) of China dual functional lithium lead-test blanket module (DFLL-TBM) for International Thermonuclear Experimental Reactor (ITER) contains rectangular helium flow channels, which will be fabricated by hot isostatic pressing (HIP)-diffusion welding with China low activation martensitic (CLAM) steel plates and rectangular tubes. Study on the rectangular tube fabrication process are being conducted. Rectangular tubes of 15 mm × 20 (inter dimensions of cross section) mm × 2.2 (wall thickness) mm × 1500 (length) mm were produced by hot piercing and cold rolling, and its dimensional deviation met the requirement of TBM assembly. The effects of tube rolling and heat treatment on microstructure and mechanical properties of CLAM rectangular tube were analyzed. It is found that soft annealing heat treatment after tube piercing was a suitable way to improve the ductility of the CLAM steel. The elongation should be less than 15% at every tube rolling step, and the favorable tempering temperature to release the stress caused by tube rolling was 800 °C.

The China Low Activation Martensitic (CLAM) steel is being developed in ASIPP (Institute of Plasma Physics, Chinese Academy of Sciences) under wide collaboration with many institutes and universities. A heat of 1.2 tons was fabricated and tested. The tested main compositions are eligible and without segregation. The tensile, Charpy impact and fracture toughness tests showed that its mechanical properties were similar to those of small ingots of CLAM steel. Also, joining techniques such as Electron Beam Welding (EBW), Hot Isostatic Pressing–Diffusion Welding (HIP–DW) and fabrication techniques of rectangular tube with CLAM steel were studied in details. And a 1/3 scaled mockup of Test Blanket Module (TBM) by P91 are being fabricated to explore TBM fabrication technology.

Aluminum oxide Al 2 O 3 coatings on China Low Activation Martensitic (CLAM) steel substrates were prepared with atmospheric plasma spray (APS) method. Corrosion experiments of the coating specimens in static liquid LiPb were carried out in DRAGON-ST capsule for 5000h at 550°C. The results showed that there is no obvious thinning of external layer Al 2 O 3 after 5000 h exposure. The γ phase Al 2 O 3 in external layer and the dissolution of Ni in liquid LiPb from the edge of the internal layer Ni-Cr were the possible reasons for the corrosion of coatings. .

In the design of liquid–metal fusion blankets, Al 2 O 3 ceramic is one of the most promising coating materials. In this study, functionally graded FeAl/Al 2 O 3 coatings were deposited on China Low Activation Martensitic (CLAM) steel substrates with vacuum plasma spraying (VPS) method. The SEM investigation revealed that the adhesion between adjacent layers in the coatings was sound. X-ray diffraction showed that stable alpha alumina dominated in the top alumina layers, while γ-Al 2 O 3 and β-Al 2 O 3 were also detected. The coating/substrate adhesive tensile strength test showed that adhesive strength of graded coatings was about 2.5 times that of duplex FeAl/Al 2 O 3 coatings. Thermal shock resistance test indicated that the graded coatings could tolerate more thermal shock cycles than duplex coatings.

The first generation of TCAP hydrogen isotope separation process has been in service for tritium separation at the Savannah River Site since 1994. To prepare for replacement, a next-generation TCAP process has been developed. This new process simplifies the column design and reduces the equipment requirements of the thermal cycling system. An experimental twelve-meter column was fabricated and installed in the laboratory to demonstrate its performance. This new design and its initial test results were presented at the 8th International Conference on Tritium Science and Technology and published in the proceedings. We have since completed the startup and demonstration the separation of protium and deuterium in the experimental unit. The unit has been operated for more than 200 cycles. A feed of 25% deuterium in protium was separated into two streams each better than 99.7% purity.

Fabrication techniques for Test Blanket Module (TBM) with CLAM are being under development. Effect of surface preparation on the HIP diffusion bonding joints was studied and good joints with Charpy impact absorbed energy close to that of base metal have been obtained. The mechanical properties test showed that effect of HIP process on the mechanical properties of base metal was little. Uniaxial diffusion bonding experiments were carried out to study the effect of temperature on microstructure and mechanical properties. And preliminary experiments on Electron Beam Welding (EBW), Tungsten Inert Gas (TIG) Welding and Laser Beam Welding (LBW) were performed to find proper welding techniques to assemble the TBM. In addition, the thermal processes assessed with a Gleeble thermal-mechanical machine were carried out as well to assist the fusion welding research.

The effect of the size and distribution of non-metal inclusions on mechanical properties of the China low activation martensitic steel (CLAM) was investigated. The tensile and Charpy V-notch impact tests showed that electroslag remelting improved the tensile properties and reduced the ductile brittle transition temperature (DBTT). Inclusion detection of CLAM by optical microscopy and scanning electron microscope showed that both the dimensions and quantities of the alumina inclusions decreased and their distributions became more uniform after remelting. The better refinement and distribution uniformity of alumina inclusions were considered as the main possible reasons for the improvement of the mechanical properties of CLAM steel after remelting.

China low activation martensitic steel (CLAM), which is one of the RAFMs and under development in ASIPP, is considered as the primary candidate structural material for blankets in FDS series fusion reactors and will be in contact with the liquid breeder LiPb, so its corrosion behavior is of significance for its successful application. In the thermal convection LiPb loop DRAGON-I, the corrosion experiment of CLAM in flowing LiPb at 480 °C was performed up to about 2500 h to evaluate the corrosion behavior of CLAM in LiPb. The exposed samples were observed and analyzed, respectively, by metallography and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy after 500, 1000, 1500, 2000 and 2500 h corrosion experiments, respectively. The results show that the corrosive attack started with the dissolution of the passivated oxides formed during the heat treatment on the surface of CLAM steel. Then the corrosive attack continued further into the steel matrix. The weight loss was about 0.38 mg/cm 2 after 2500 h exposure.

Preliminary Hot Isostatic Pressing (HIP) diffusion bonding experiments on China Low Activation Martensitic (CLAM) steel have been performed. A few approaches such as dry turning, grinding and mechanical-polishing, etc. were used to prepare the samples’ surfaces. Different capsule sealing techniques were used as well. The HIP parameters are 140 MPa/3–4 h/1323–1423 K. Then post-HIP heat treatment (PHHT) was done. The tensile properties of HIPed joints of 1373 K and 1423 K with dry-turned or ground joining surface are identical to those of the base material. But the Charpy impact absorbed energy of the joints is a little low and further research is needed to increase it.

The liquid metal LiPb blanket design is one of the most promising designs for future fusion power reactors and under wide research in the world. The first liquid metal LiPb loop in China named DRAGON-I was built in 2005 in order to do research on characteristics of liquid metal LiPb such as its corrosion to structural materials of the blankets and so on. The first corrosion experiment in flowing LiPb with a speed of 0.08 m/s at 480 °C for 500 h was done in October 2005 on CLAM (China low activation martensitic) steel and 316L stainless steel for comparison. The weights and compositions, etc. of the specimens before and after corrosion experiment were tested and analyzed, the microstructures of the specimens were also inspected by SEM. The results show that the corrosion of CLAM steel is relatively slight, while that for 316L is obvious and very serious. Further study on corrosion behavior of CLAM for longer time experiment in liquid LiPb at different temperatures and flow speeds will be carried out in the near future.

Using V–4Cr–4Ti as structural material in a V–Li blanket offers the blanket to operate at 350–750 °C with high thermal efficiency. This paper investigates ways to strengthen V–4Cr–4Ti and the thermal stability of the strengthening. Results show that the alloy could be greatly strengthened in a proper ageing process, with insignificant loss of ductility or even higher static tensile fracture toughness. Cold rolling is found to be another approach for higher strength. Both strengthening are thermally stable at not more than 500 °C. At higher temperature, the alloy in the sate of complete recrystallization shows better thermal stability than the alloy in solid solution state. For high performance of the V–Li blanket with good economic feature, the design of the blanket should consider to use V–4Cr–4Ti in various thermo-mechanical states in terms of the operation temperature.

LiPb auxiliary system is an important external loop equipment of test blanket module (TBM) for liquid LiPb blanket design. According to the requirement of testing strategy of DFLL (dual functional lithium lead) TBM, which could demonstrate the technology of the SLL (single-coolant lithium lead) and the DLL (dual-coolant lithium lead) blankets, a conceptual design of the LiPb ancillary system is done, which could serve to achieve the dual functions. The auxiliary system can be used to achieve the recovery of tritium, heat rejection, monitoring of impurity in LiPb, LiPb purification and so on. It consists of detritiation unit, LiPb to He heat exchanger, plugging indicator, LiPb purification system and pumping system, etc.