Retention Principles Of Deuterium In Chinese Reduced Activation Ferritic/Martensitic Steels

Reduced Activation Ferritic/Martensitic (RAFM) steels have been considered as the most promising candidate structural materials for a fusion reactor. In the recent decade, two new types of domestic RAFM steels, called China Low Activation Martensitic (CLAM) steel and China Low-activation Ferritic (CLF-1) steel, have been developed. In the real condition, structural materials will be faced with strong neutron radiation, high heat load and tritium inventory. Hydrogen retention generated embrittlement and helium decayed by tritium embrittlement or damage should be considered. As a substitute of tritium, deuterium is used to investigate the transport behavior of hydrogen isotopes and mechanical performances.The gas evolution permeation technique has been used to investigate diffusive transport parameters of deuterium through CLAM and CLF-1 over the temperature range 623-873K at deuterium pressure of 105Pa. The resultant transport parameters are:Φ(mol·m-1·s-1·Pa-1/2)= 5.40×10-8exp(-46.8(kJ-mol-1)/(RT)), D(m2·s-1)=3.81 × 10-7exp(-24.0(kJ·mol-1)/(RT)) and 5(mol·m-3·Pa-1/2)=1.42×10-1exp(-22.8(kJ·mol-1)/(RT)) for CLAM; whileΦ(mol·m-1·s-1·Pa-1/2) = 1.76×10-8exp(-43.9(kJ·mol-1)/(RT)), D(m2·s-1)=1.02×10-7exp(-16.9(kJ·mol-1)/(RT)) and S(mol·m-3·Pa -1/2)=1.73×10-1exp(-27.0(kJ·mol-1)/(RT)) for CLF-1. The results show that both RAFM steels possess one or two magnitudes of higher deuterium diffusivities, several times of lower deuterium solubilities and one magnitude of higher deuterium permeabilities than 3xx types of austenitic stainless steels; CLAM is slightly more permeable than CLF-1 resulting in relatively easier removal of the deuterium retained in the metal.Hydrogen damage effect on the mechanical properties is also investigated with tensile performance determination. The shrinkage rates of hydrogen induced reduction of area of CLAM steel and CLF-1 steel are 18.65% and 45.98%, respectively, which shows poorer resistance to hydrogen embrittlement compared to the 3xx types of austenitic steels. And the mechanism of even more sensitive to hydrogen damage for CLF-1 steel is probably due to its lower Cr content caused poorer trap and higher Ta content caused strongly trap to hydrogen interstitials, and the structure of temper martensite in lath structure together with more grain boundaries for entrapping hydrogen atoms. Thus CLF-1 possesses stronger capability to retain hydrogen isotopes as a result of more severe degradation of the mechanic performance than CLAM.