Journal of Nuclear Science and Technology

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Radiation Blistering of Vanadium 4

Irradiated with 40keV He Ions a

a

a

Kimio HAYASHI , Nobuharu IIDA , Shiori ISHINO & Yoshitsugu MISHIMA

a

a

Department of Nuclear Engineering , University of Tokyo , Hongo, Bunkyo-ku, Tokyo Published online: 15 Mar 2012.

To cite this article: Kimio HAYASHI , Nobuharu IIDA , Shiori ISHINO & Yoshitsugu MISHIMA (1977) 4

Radiation Blistering of Vanadium Irradiated with 40keV He Ions, Journal of Nuclear Science and Technology, 14:10, 765-767, DOI: 10.1080/18811248.1977.9730835 To link to this article: http://dx.doi.org/10.1080/18811248.1977.9730835

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Vol. 14, No. 10 (Oct. 1977)

SHORT NoTE (K. Okamoto; K. Hayashi et al.)

Yamanaka of Osaka University and Prof. A. Miyahara of Nagoya University for their helpful discussions and advice. He is also very grateful to Dr. W.B. Lewis of Los Alamos Scientific Laboratory for providing unpublished numerical values of the HartreeFock wave functions of the uranium atom.

(5) (6) (7) (8)

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---REFERENCES--MoRITA, M.: Progr. Theoret. Phys., 49, 157-! (1973). (2) 0TOZAI, K.: Butsuri, (in Japanese), 30, 273 (1975). (3) 0TOZAI, K., ARAKAWA, R., MoRITA, M.: Progr. Theoret. Phys., 50, 1771 (1973). (4) OKAMOTO, K. : Paper presented at the 4th Int. Workshop on "Laser Interaction and Related

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(101 (11)

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Plasma Phenomena" at Rensselaer Polytechnic lnst., Troy, New York, 8-12 Nov. 1976. MAZAKI, H., SHIMizu, S.: Phys. Lett., 23, 137 (1966). Neve de MEVERGNIES, M. : ibid., 328, 482 ( 1970). CuLLER, B.E.B.: LBL-221, (1971). McGowAN, F.K., BEMIS, C.E., Jr., MILNER, W.T., FoRD, ].C.L., Jr., RoBINSON, R.L., STELSoN, P.H.: Phys. Rev., toe, 1146 (1974). LEWIS, W.B., MANN, J.B., LIVERMAN, D.A., CROMER, D.T.: ]. Chem. Phys., 53, 809 (1970). Numerical values of the wave functions were kindly provided by Dr. Lewis. RuDGE, M.R.H. : Rev. Mod. Phys., 40, 564, Eq. ( 4.5)' (1968). GoLDANSKII, V.E., NAMIOT, V.A.: Phys. Lett., 628, 393 (1976). HoRA, V.H., LocHTE-HOL TGREVEN, W. : Atomkernenergie, 25, 53 (1975).

Journal of NucLEAR SciENCE and TEcH:>:OLOGY, 14(10), pp. 765-767 (October 1977).

SHoRT NoTE

Radiation Blistering of Vanadium Irradiated with 40 keV 4He Ions Kimio HAYASHI, Nobuharu IIDAt, Shiori ISHINO and Yoshitsugu MISHIMA

Department of Nuclear Engineering, University of Tokyo* Received May 23, 1977

KEYWORDS: radiation effects, blisters, controlled thermonuclear reac· tors, first wall, annealing, scanning electron microscopy, flaking, hole, critical doses, irradiation, helium ions

Radiation blistering can be an important erosion process of first wall material of a future controlled thermonuclear reactor (CTR). Many studies have been made on He irradiated Nb and Moe!). But few, except Bauer & Thomas's studyC 2 Jcal, have been made on V, especially for low He energies. The present work deals with the blistering of V irradiated

with 40 ke V 'He ions at room temperature and subsequently annealed at high temperature. Most of the publications so far have dealt with radiation blistering at high temperatures, whereas the present experiment concerns with radiation blistering at low temperature and anneal-blistering at high temperatures, the results of which are of interest in comparison with those of radiation blistering at high temperatures. Polycrystalline vanadium wafers, 14 mmx 9 mmx0.1 mm, were used. Main impurities of the specimens were 0.05% 0, 0.01% N, 0.005% C, 0.04% Fe, 0.025% Cr, 0.015% Al and 0.01% Si. The targets were first mechanically polished, and annealed at 9oo·c in a vacuum of 2x 10· 6 Torr for 90 min. followed by electropolishing. Irradiations were done at ambient temperature with mass-analysed beams of 40 keY 'He ions from a 200 kV Cockcroft accelerator. Fluxes of 3"-6X 10 14 He/cm 2 ·sec were used, and the vacuum in the target chamber was kept 2x 10· 6 Torr during the irradiations. The temperature of the targets was risen to 80"'

* Hongo, Bunkyo.ku, Tokyo. t

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Present address: Japan Nuclear Utility Service, Chiyoda-ku, Tokyo.

766

SHORT NoTE (K. Hayashi et al.)


220'C by beam heating. The targets were annealed after the irradiations at 400, 700 and 1,000'C in a vacuum of 2x 10-s Torr for 1 or 2hr. Photography l(a) shows a scanning electron micrograph (SEM) of the specimen irradiated with 4 He to a dose of 2X 10 18 He/cm 2 at room temperature. Large-scale flaking at the surface is observed. Photography l(b) shows a SEM structure of the same target as Photo. 1(a) but annealed at 1,000'C for 1 hr. There have appeared a number of holes all over the flake skins.

]. Nucl. Sci. Techno/.,

bubbles nearby coalesced again to form the latter, large blisters, while the specimen was annealed. In this note the former are referred to single blisters, the latter coalescent blisters. Some of the coalescent blisters are found to be broken off, probably due to the pressure of the implanted He gas in the blisters.

Photo. 2 Optical micrograph of V irradiated with 40 keV 4He ions to a dose of 2 x 10 17 He/cm 2 at room temperature and subsequently annealed at 700'C for 2 hr

In Photo. 3, typical blisters, approximately round in shape and rv5 p.m dia., are observed. Blisters are found to be dense in one grain, but scarcely found in another grain. All over the surface a number of holes are found, especially on the grain boundaries the holes being seen to be larger.

Photo. 1 Scanning electron micrograph of V irradiated with 40 keV 4He ions to a dose of 2 x 10 18 He;cm 2 at room temperature (a), and annealed thereafter at 1,000'C for 1 hr (b)

In Photo. 2, some of the blisters are seen to be small and round in shape, whereas others are large and have irregular shapes. It seems that the bubbles of the implanted He ions coalesced to form the former, small blisters, and that some close blisters together with

Photo. 3 Scanning electron micrograph of V irradiated with 40 keV 4 He ions to a dose of 2 x 10 17 He;cm 2 at room temperature and subsequently annealed at 1,000'C for 1 hr

The observed flakes, blisters and holes are similar in shape to those reported in Bauer & Thomas's studyc 2 )ca) of radiation blistering of

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Vol. 14, No. 10 (Oct. 1977)

767

SHORT NoTE (K. Hayashi et al.)

Table 1 Conditions of irradiations and subsequent annealings and results of surface observations of V irradiated with 40 keY 4He ions Annealing after irrad. temp. time (•C) (hr) As irrad. (80-220)

400


700

2

2

1,000

o:

Observed,

Dose (He/cm

Critical dose

Blister 2)

Flake

Hole

X X

X X X

Single

Co ales

5 X 10 16 2 X 10 17 2 X 10 18

X X X

X X X

5 X 10 16 2 X 1017 2 X 10 18

X X X

X X X

5 X 10 16 2 X 10 17 2 X 1018

X

X

X

X

0

0

X

X X

5 X 10 16 2 X 10 17 2 X 10 18 x: Not observed,

X X

0 0

!:::,

X

X

!:::,

0

0

X

0 0

!:::,

!:::,

2 X 10 17 -2 X 10 18

X X X

!:::,

!:::,

6:

0

(He;cm 2 )

0

" 5 X 10 16 -2 X 10 17

"

Observed only at a part of the surface

V at high temperature. But holes around blisters or those over the flake skins have not been observed by them in V or by other authorsc 1 ' in Nb and Mo at high temperature. It appears that those holes have been formed by re-emission of He gas from small bubbles distributed over range straggling region of implanted He ions near the surface of the specimen around blisters or in flake skins. Table 1 summarizes the conditions of irradiations and subsequent annealings together with the results of surface observations of the V specimens. It has been known that there is a critical dose for appearance of blisters. One sees from Table 1 that for V as irradiated or subsequently annealed at 4oo·c the critical dose is between 2X 10 17 "-'ZX 1018 He/cm 2 • But for the specimen annealed at 700 or 1,000"C after the same irradiations the critical dose decreases to between 5x 1016 "-'ZX 1017 He/cm 2 • The decrease in the critical dose with increasing temperature is consistent with previous

studies on radiation blistering0 ' and with Bauer & Thomas's study of He re-emission during 300 keV He implantationc 2 '. The authors would like to thank Dr. N. Terasawa, Dr. T. Ozaki and Dr. M. Shimada of Research and Development Center, Toshiba Electric Co. Ltd. for the use of the accelerator. They are also indebted to Mr. M. Adachi for SEM observations. ---REFERENCES---

e.g. DAs, S.K., KAMINSKY, M.: J. Nucl. Mater., 53, 115 (1974) ; RoTH, ]., et al.: ibid., 53, 147 (1974) ; McCRACKEN, G.M., MAPLE, J,C.: Brit. ]. Appl. Phys., 18, 919 (1967). (2) BAUER, W., THOMAS, G.J,: Proc. Int. Conf. Defects and Defect Clusters in b.c.c. Metals and Their Alloys, (ed. R.J, ARSENAULT), 255 (1973) ; Nucl. Met. 18, 225 (1973). (3) THOMAS, G.]., BAUER, W.: ]. Nucl. Mater., 53, 134 (1974). (1)

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