fabrication of an iter middle-scaled shielding blanket module mock-up

Fusion Engineering and Design 39–40 (1998) 765–773

Fabrication of an ITER middle-scaled shielding blanket modulemock-up

Shinichi Sato a,*, Toshio Osaki a, Hirokazu Yamada a, Takeshi Kobayashi a,Satoshi Sato b, Kazuyuki Furuya b, Toshihisa Hatano b, Ikuhide Tokami c,

Toshimasa Kuroda b, Hideyuki Takatsu b

a Nuclear Systems Di6ision, Kawasaki Hea6y Industries, Minamisuna, Koto-ku, Tokyo 136, Japanb Blanket Engineering Laboratory, Naka-JAERI, Naka-machi, Ibaraki-ken 311-01, Japan

c Kumagai Gumi, Onigakubo, Tsukuba-shi, Ibaraki-ken 300-22, Japan

Abstract

In the present ITER shielding blanket design, the first wall (FW) has built-in cooling channels (SS316LN) in acopper layer that is bonded to the shielding structure (SS316LN). The shielding structure is a SS block also withcooling channels that are drilled. For fabricating the shielding blanket and the FW, hot isostatic pressing (HIP) hasbeen proposed as a promising joining method to avoid fusion welds under severe neutron irradiation. To demonstratethe fabricability of the FW/blanket, a middle-scaled mock-up was fabricated. The mock-up consists of FW, shieldingblock, and cooling header, etc. The FW was fabricated using a sandwiched tube technique (DSCu plate and SS316Lcircular tube), which was composed of a 20-mm thick DSCu heat sink containing SS cooling tubes orientedpoloidally. The FW is curved in the poloidal direction corresponding to one of inboard modules (No. 6 module). Thecooling channels of the SS316L shielding block were machined by the drilling method. The FW parts (SS tubes andDSCu plates) and the shielding block were bonded by single-step HIPing. After HIP bonding, microscopicobservations of bonded interfaces using the remnant (edge of the mock-up) were carried out. Also, to confirm theintegrity of pressure boundaries, pressure-resistant and helium leak tests were performed. It has been shown that themiddle-scaled mock-up was successfully fabricated using a sandwich-tube technique by single step HIPing. © 1998Published by Elsevier Science S.A. All rights reserved.

1. Introduction

During the basic performance phase of anITER operation, modularized shielding blanketintegrated with the first wall (FW) will be in-stalled. The shielding blanket/FW has the follow-ing functions:

1. It removes surface heat flux and nuclear heat-ing to keep material temperatures and stresseswithin allowable limits,

2. It reduces the nuclear responses in the super-conducting magnets and vacuum vesselstructure,

3. It contributes to the passive stabilization ofthe plasma.* Corresponding author.

0920-3796/98/$19.00 © 1998 Published by Elsevier Science S.A. All rights reserved.

PII S0920-3796(97)00195-6

S. Sato et al. / Fusion Engineering and Design 39–40 (1998) 765–773766

Fig. 1. Configuration of the ITER shielding blanket module.

Also, the shielding blanket/FW structure mustendure the huge electromagnetic force due to aplasma disruption.

In the present ITER shielding blanket design,the FW has built-in cooling channels (SS316LN)in a copper layer (DSCu: dispersion strengthened

S. Sato et al. / Fusion Engineering and Design 39–40 (1998) 765–773 767

Fig. 2. Isometric view of a middle-scaled shielding blanket mock-up.

copper) that is bonded to the shielding structure(SS316LN). The shielding structure is aSS316LN block with drilled cooling channels.

A middle-scaled shielding blanket mock-uphas been fabricated to investigate the feasibilityof the fabrication techniques and to clarify tech-nological issues. For fabricating the mock-up,simultaneous hot isostatic pressing (HIP) hasbeen applied.

2. Configuration of shielding blanket module

Fig. 1 by Furuya [1] shows an isometric viewof the ITER blanket module (a) and a cross-sec-tional view of the midplane module (b). In thisconcept, modularized shielding blanket inte-grated with the FW will be installed. A FW hasbuilt-in cooling channels in a copper layer thatis bonded to the shielding structure. Beryllium is


Fig. 3. Horizontal cross-section of the mock-up.

used as armor material facing plasma and DSCuas heat sink material as noted in the IAEA de-sign report [2] and Sato [3].

For ITER machine fabrication, one of the keyissues is to establish the fabrication procedure ofcurved blanket module and to confirm thesoundness of some different joints, i.e. Cu–Cu,Cu–SS and SS–SS.

3. Detail of a middle-scaled mock-up

3.1. O6erall configuration

Fig. 2 shows an isometric view of a middle-scaled shielding blanket mock-up. FW is curvedin the poloidal direction corresponding to one ofinboard modules (No. 6 module). The main di-mensions are as follows:

800H×412−521W×329−361T (mm)

The radius of the curvature is :1300 mm in thepoloidal direction, and straight in the toroidaldirection. In the top/bottom FW corner, the ra-dius of curvature is :50 mm. The FW is inte-grated with the shielding block. Coolant headers

for FW and the shield block are arranged insidethe mock-up. On the back wall surface, inlet/out-let coolant pipes are installed.

3.2. FW cooling channel construction

A horizontal cross-section of the mock-up isshown in Fig. 3. The FW total thickness is 20mm, with 21 circular SS tubes of 12 mm in theouter diameter and 1 mm in thickness embeddedin the copper layer.

Also in the mock-up, the pitch of the FWcooling channel varies from the top to the bot-tom. The FW cooling channel pitch is :23.3mm at the top part of the mock-up and :20.7mm at the bottom. Fig. 4 shows the FW cross-sections at the top of FW (a) and the bottom ofFW (b).

FW armor (Be) is not incorporated for thismock-up fabrication.

3.3. Shielding block cooling channel construction

The shielding block is cooled by water in thepoloidal direction. As shown in Fig. 3, the mockup has five rows of cooling channels oriented


poloidally. The dimension of shield cooling chan-nel is 24 mm in diameter (two rows near the FW)and 40 mm in diameter (three rows near the backwall). In this mock-up, cooling channels inclinesfrom the top to the bottom as if FW aremachined.

4. Materials

As DSCu, Glidcop® AL-25 LOX grade plates(declad) was applied. These declad plates werecross rolled (transverse to the extrusion direction)to the appropriate width, and finally straight-rolled (in extrusion direction). As circular tubematerial, SS316L tubes were applied, which wereprovided following the Japan Industrial Standard(JIS).

SS316L forged block also following JIS wasapplied to the shielding block material. Materialof the other parts of the mock-up, i.e. inlet/outlettube and flange is SS304, was provided in JIS.

5. Fabrication procedure

5.1. FW parts fabrication

Fabrication procedure of FW parts is shown inFig. 5. On the surface of DSCu plates, semicircu-lar grooves were machined. The diameter of thegroove was 13 mm to fit SS circular tubes of 12mm in diameter into the groove. This groovedimension was based on the results of a prepara-tory investigation. The circular tubes and DSCuplates were bent at room temperature by a three-point bending method. After bending, the surfaceof the circular tubes and DSCu plate was polishedby buffing. Then, the circular tubes were sand-wiched by the two DSCu plates and assembled.Roughness of the surface to be bonded, whichwas one of the most important parameters forHIPing, was less than 2 mm, Rz.

5.2. Shielding block fabrication

The fabrication procedure for shielding theblock is shown in Fig. 6. At the first step, somedrill holes were machined in the poloidal directionby a radial drilling machine. The drillings wereperformed from both sides of the shielding block.

Next, the drilled shield block was bent in thepoloidal direction (R=1273 mm) at room tem-perature. A three-point bending method was ap-plied. In order to prevent the drill holesdeforming during bending, aluminum alloy barswere inserted into the drill holes. The pressingcapacity of the radial bending machine used was10000 ton.

After the bending, solution heat treatment com-bined with the melting of aluminum alloy barswas performed. The shielding block was annealedunder the air atmosphere at 1010–1054°C for 670min and cooled by water.

Next, at the edge region of the shielding block,the coolant header area were machined and theFig. 4. Cross-sectional view of the first wall.


Fig. 5. Fabrication procedure of first wall parts.

lids were jointed by tungsten inert gas (TIG)welding. The lids’ material is SS316L, and thethickness is 3 mm.

After welding, a penetration test (PT) was per-formed to confirm the soundness of the weldedjoints. No indications of cracks were found, thussound weldability was confirmed. The surface ofthe shielding blanket was finally machined andpolished by buffing. Surface roughness was lessthan 2 mm, Rz.

5.3. Mock-up fabrication by HIPing

The appearance of the assembled mock-up isshown in Fig. 7. Assembled gaps between eachpart of FW and the shielding block were less than2 mm. After assembling the FW parts and shield-ing block that were machined by the above

method, a single-step HIPing was performed. Be-fore HlPing, in order to form a vacuumboundary, a SS304 can was welded by TIG weld-ing. After canning, outgassing was performedwhile the mock-up was heated in air atmosphere.The heating temperature was :500°C. The pres-sure at the interface to be HIPed after outgassingwas less than 10−5 Torr.

The adopted HIP condition is shown in Fig. 8.The HIP temperature was 1050°C, holding timewas 2 h, and the pressure by argon gas was 150MPa. The temperature during the HIP processwas maintained within 910°C. The final appear-ance of the middle-scaled mock-up is shown inFig. 9. The final accuracy (outward form) afterthe mock-up fabrication was within 90.8 mm,and the total thickness of FW (DSCu) was 19.1–19.3 mm.


Fig. 6. Fabrication procedure of shielding block.

Fig. 7. Assembly of the middle-scaled mock-up.

6. Mock-up inspections

6.1. Pressure-resistant and He leak tests

Pressure-resistant and He leak tests were con-ducted after the mock-up fabrication to confirm

the soundness of the HIP bonded parts and pres-sure boundary. For the pressure-resistant test, thetest pressure was 6 MPa and the holding time was30 min. No decrease of pressure was observed.Also, from the He leak test results, the leakquantity was less than 10−9 Torr 1 s−1.


6.2. Metallurgical obser6ation of HIP bondedparts

In order to confirm the soundness of the HIPbonded parts, a metallurgical observation wasperformed after HIP bonding using the remnant(edge of the mock-up). One of macro-structuresof the bonded interfaces is shown in Fig. 10.

In Fig. 10, HlP-bonded parts of SS316L circu-lar tubes/DSCu, DSCu/DSCu and SS316 plate/DSCu at the curved region of the mock-up areshown. A little deformation of the SS316L circu-lar tube diameter was observed. This deforma-tion of the tube diameter is caused at the tubebending, and due to the assembling gap betweenthe circular tube and the DSCu plates beforeHIPing.

An example of the micro-structure of HIPbonded parts is shown in Fig. 11. By metallurgi-cal observation, no defects (voids) were observedat the bonded interface. Also, a re-crystallizationstructure of DSCu was not observed. Thus, goodbondability by HIPing can be concluded.

7. Conclusion

To demonstrate the fabricability of the FW/blanket, a middle-scaled mock-up was fabricatedby single step HIPing. The following conclusionshave been obtained.

Fig. 9. Final appearance of the middle-scaled mock-up.

A middle-scaled ITER shielding blanket mod-ule with a curved FW in which circular tubeswere embedded in a DSCu plates was success-fully fabricated.

Fig. 8. HIP condition.Fig. 10. Cross-sectional view of FW (cut from the edge of themock-up).


Fig. 11. Micro-structure of HIPed interface (DSCu/SS circular tube).

will be performed to evaluate the integrity of theHIP bonded interfaces.

References

[1] K. Furuya, S. Sato, T. Kuroda, H. Miura, T. Kurasawa,I. Tokami, T. Hatano, H. Takatsu, Fabrication of Small-scaled Shielding Blanket Module and First Wall Panel forInternational Thermonuclear Experimental Reactor,Proc. 19th Symp. Fusion Technology, Lisbon, 1996.

[2] IAEA, Technical basis for the ITER interim design re-port, Cost Review and Safety Analysis, ITER EDA Doc-umentation Series, 7, 1996.

[3] S. Sato, T. Hashimoto, T. Kurasawa, T. Kuroda, K.Furuya, I. Togami, H. Takatsu, Mechanical Property ofHIP Bonded Materials for Fusion Experimental ReactorBlanket, Proc. ICFRM-7, Obninsk, 1995.

The simultaneous HIP bonding of SS316L/DSCu, SS316L/SS316L, DSCu/DSCu was suc-cessfully conducted and no injurious defects(voids) were observed.

For fabricating FW, a sandwich technique wasused, and its applicability was demonstrated.

Engineering data, such as HIP condition, as-sembling accuracy, deformation after HIPing,were obtained for the fabrication of the blanketmodules by HIP bonding.

After the fabrication, pressure-resistant test, Heleak test and metallurgical observation were per-formed to confirm the soundness of the mock-up.From these test results, there were no injuriousdefects observed.

Using this mock-up, thermo-mechanical tests

.

fabrication of an iter middle-scaled shielding blanket module mock-up

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