Nuclear Fusion Research and Development

4-2

Manufacturing of ITER Divertor Prototype－ First Step toward Manufacturing of Actual ITER Divertor －（a）（b）

Inner vertical target(EU)
Outer vertical target(JA)

Dome(RF)〜3.5 mIn
the high heat flux test, a heat
加熱試験では上の写真の黄色枠の部
22 for 1000 cycles
fluxof 20
MW/m
分に20MW/mの熱負荷で1000回のwasappliedto theした
tungsten armor
繰り返し加熱を実施(bounded by yellow).

Cassette body(EU)

Fig.4-4 ITER divertor (cassette structure)
The ITER divertor has a cassette structure. High heat
flux components, such as the inner vertical target, outervertical target, and dome, are installed in the cassettebody. There are 54 cassettes in the tokamak.

The Japan Atomic Energy Agency (JAEA), designatedas the Japanese Domestic Agency (JADA), is currently
manufacturing various components for ITER construction.
The ITER divertor components are being manufactured bythree parties (the European Domestic Agency (EUDA), theRussian Federation Domestic Agency (RFDA), and JADA).
The JADA is responsible for manufacturing the outer verticaltarget shown in Fig.4-4.
The divertor exhausts impurities that come from the plasma.
The divertor plate is subjected to a high heat flux from theimpact of the impurities. To withstand the high heat flux,
the surface of the divertor plate is covered with refractorymaterials. The inner target and outer target, which are subject
to severe heat flux, are covered with carbon fiber composite,
and the other components are covered with tungsten. Thesearmor materials are metallurgically bonded to the copper
alloy (CuCrZr) cooling tubes to achieve a high heat removal
capability. Unique technologies that have been independently
developed by the three parties are used to bond the armor
materials and the cooling tubes. The JADA currently uses
a brazing technology for the bonding. In the ITER project,
qualification of the manufacturing process for the divertor

Fig.4-5 Appearance of prototype PFU and tungsten armor(a) Test frame with four PFUs.
(b) Tungsten armor tiles after high heat flux test. Tungsten has
recrystallized. However, no degradation of the heat removal
capability was found through 1000 cycles at 20 MW/m2.

must be demonstrated by each party to validate its technicalcapability. The parties manufacture prototype componentsthat consist of the same materials that will be used for the realcomponents and perform a high heat flux test to demonstrate
the durability of the prototype components.
The JADA manufactured the first set of plasma-facing
units (PFU#1) as a first step in manufacturing the divertor, as
shown in Fig.4-5. PFU#1 has been transported to the RFDA
for a high heat flux test in the RFDA’s facility. Before themanufacturing of PFU#1, the JADA conducted qualification
activities, such as mechanical and nondestructive testing of
the braze joints and welding joints. In addition, the brazing
process was formally witnessed by the ITER organization
during the manufacture of PFU#1. In the high heat flux testin the RFDA, PFU#1 showed excellent durability against arepetitive heat flux of 20 MW/m2 for 1000 cycles with nodegradation of the heat removal capability and no surface
crack initiation.
The second high heat flux test campaign in the RFDA isscheduled for autumn 2013. After that, the manufacturing of
the real divertor components will begin.

Reference
Suzuki, S. et al., Development of the Plasma Facing Components in Japan for ITER, Fusion Engineering and Design, vol.87, issues 5-6, 2012, p.845-852.

JAEA R&D Review 201351