D. Hamaguchi

D. Kato

H. Iwakiri

K. Kikuchi

N. Yoshida

S. Kawamura

T. Muroga

National Institute for Fusion Science (NIFS-Repository)

Trapping behavior of deuterium in F82Hferritic/martensitic steelIwakiri, H. (Univ. Ryukyus), Hamaguchi, D. (JAEA), Kikuchi,K (JAEA) Kawamura, S (Kyushu Univ.) Yoshida, N. (KyushuUniv.), Muroga, T., Kato, D.For the development of fusion reactor materials, thecharacterization of trapping and releasing behavior ofhydrogen and its isotopes is one of the key issues consideringthe influences on plasma parameters and tritium inventory.Low activated F82H ferritic/martensitic steel is one of acandidate alloys for the first wall of fusion reactors as well asfor the beam window of spallation target for ADS. In thisstudy, trapping behavior of deuterium in F82H under lowenergy helium irradiation was studied by means of thermaldesorption spectrometry (TDS) and TEM in order tocharacterize the trapping behavior of deuterium on irradiatedmaterials.The reduced activated F82H ferritic/martensitic steel used inthis study was IEA-heat 4-20 prepared for Japanese fusionreactor material program. The samples with a dimension of6�10mm were mechanically cut to the thickness of around2mm. Then the surfaces of the samples were mechanicallypolished up to buff polishing with 0.03�m colloidal silica forlow energy ion irradiations. Some samples were preparedfrom a tempered material at 790 ºC for 30 minutes in order toreduce the influence of deuterium trapping by dislocations forcomparison with the normalized materials. The temperingcondition was estimated form former studies.Low energy helium and deuteron irradiations were performedat Research Institute for Applied Mechanics, KyushuUniversity. The specimens were first irradiated with 5keV He+ions at 600ºC followed by the additional irradiations with0.5keV D2+ ions at RT. The deuteron irradiation energy of0.5keV is that without any introduction of displacementdamage into Fe-based alloys.After the irradiations, thermal desorption of D2 and He underheating with a ramping rate of 1 K/s were measured with highresolution quadruple mass spectrometer. This high resolutionspectrometer enables to distinguish slight differences in themass between He (m=4.0026) atom and D2 (m=4.0282) gas.The desorption rates of He and D2 were quantitativelycalibrated by using standard He leak with specific relativeionization efficiency. At the same time, the samples for themicrostructural study by TEM were prepared using focusedion beam system (FIB) from the same specimens.Thermal desorption spectra of deuterium from tempered andnormalized specimens are given in fig.1. Note that thedeuterium ion irradiation was carried out with very low energyof 0.5keV, where no displacement damage will be introducedin Fe-based alloys. The microstructures for these specimensare shown in fig.2. There were two desorption stages fordeuterium observed for F82H. One appears between thetemperatures from 350K to 500K and the other from around800K to 1000K. These stages were seen on both tempered andnormalized specimens. Desorption stage at lower temperatureis typical for Fe-Cr based alloy. This stage is assumed to be arelease of deuterium mainly trapped on dislocations, since thestage also appears on the cold worked Fe-9Cr alloy though itdisappears after annealing. On the other hand, the stage athigher temperature is unique to F82H. From themicrostructural observations, growth of the grins and reductionin dislocation density was observed after tempering at 790ºCfor 30 minutes. In addition, the density of carbides decreasedrapidly after tempering. Since the stage at higher temperatureappears on both tempered and normalized specimens and totaldesorption decreased to about half on tempered specimens,this stage at higher temperature is mainly attributed to thedeuterium trapped by the carbides.Fig.1. Comparison of the D2 desorption spectra betweennormalized specimen and tempered specimen without He+irradiations.Fig.2. Microstructures of the normalized and tempered F82H.256§11. Trap in  B vior of Deuterium in F82H Fe ri rtensitic St elakiri, H. (Univ. Ryukyus), Hamaguchi, D. (JAEA), ikuchi, . (JAEA), Kawamura, S. (Kyushu Univ.), Yoshida, N. (Kyushu Univ.), Muroga, T., Kato, D.

Trapping Behavior of Deuterium in F82H Ferritic/martensitic Steel

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