01Dp03
液体リチウム鉛回転流動場における機能性セラミックス被覆の共存性試験
Compatibility tests of functional ceramic coatings with liquid lithium-lead under rotating flow
赤星 江莉加1, 八木 重郎2, 向井 啓祐2, 小西 哲之2, 菱沼 良光3, 田中 照也3, 近田 拓未1Erika Akahoshi1, Juro Yagi2, Keisuke Mukai2, Satoshi Konishi2,
Yoshimitsu Hishinuma3, Teruya Tanaka3, Takumi Chikada1
1

静岡大学，2京都大学，3核融合科学研究所
1Shizuoka Univ., 2Kyoto Univ., 3NIFS

1. Introduction
Tritium permeation through structural
materials in fusion reactor blanket systems is acritical issue from the perspectives of fuel lossand radiological safety. Ceramic coatings havebeen investigated as a tritium permeation barrier
andshown
highpermeation
reduction
performance. In liquid blanket concepts, however,corrosion of the coatings by liquid tritium
breeders such as lithium-lead (Li-Pb) is anunavoidable concern. Recently, the Li-Pb
corrosion resistance of the single-layer andmulti-layer coatings was investigated in static
conditions [1,2]; however, a limited number ofreports investigating in flowing conditions areavailable. Therefore, in this study, the Li-Pb
exposure tests under rotating flow wereconducted using the coatings with various layer
structures to investigate the effect of layer
structure on the compatibility with flowing Li-Pb.
2. Experimental
Reduced activation ferritic/martensitic steel
F82H (Fe-8Cr-2W, F82H-BA07 heat) plates wereused as substrates. The coating procedure including
formation of chromium oxide (Cr2O3) on thesubstrate, dip-coating of the coating precursors,
drying, pre-heat treatment, and heat treatment is
described in detail in Ref. [2]. The layer structuresof the coatings are summarized in Fig. 1. The heattreatment was performed every time after preparing
each layer for crystallization.
Li-Pb exposure tests under rotating flow wereperformed using a rotating apparatus at 550 ºC for
100-500 h with a rotating speed of 200 rpm. The
samples were fixed to the rotating blades bystainless steel wires so that the flow velocity on thesamples is calculated to be approximately 0.37 and0.57 m/s. Surface and cross-sectional observationsof the exposed samples were conducted by scanningelectron microscopy (SEM) with energy dispersive
X-ray spectroscopy.
3. Results and discussion
A difference in surface morphology dependingon the flow velocity was confirmed after theexposure test for 100 h, while was not after the testfor 500 h. After the test for 500 h, cracks wereobserved in Samples A and C. In Sample B,
swelling of the coating was observed, and ironoxide was detected under the swelled coating. Fromthese results, an acceleration of corrosion caused byLi-Pb flowing was confirmed. Moreover, it was
found that the oxygen was supplied to the substrate
through the ZrO2 coating to a certain depth underflowing conditions. To improve Li-Pb compatibilityof the coating under flowing conditions, it isnecessary to take into consideration oxygen supply
to the substrate through the coating in addition toflow-accelerated corrosion.

Iron oxide

Coating10 µm
Fig. 2 Surface SEM image of Sample B after Li-Pbexposure test under rotating flow at 550 ºC for
500 h with flow velocity of 0.37 m/s.

Reference[1] M. Matusnaga et al., J. Nucl. Mater. 511 (2018)534-543.
[2] E. Akahoshi et al., Fusion Eng. Des. 160 (2020)
111874.
Fig. 1 Layer structure of coating samples.