S1-3
Wプラズマ対向材料－He冷却ダイバータ機器の開発
Development of He-Cooled Divertor System and W Plasma Facing Material横峯健彦1)、上田良夫2)、徳永和俊3)、結城和久4)、秋吉優史5)、佐竹 信一6)、伊庭野健造2)、
大原 健1)、Minami Yoda7), Adrian S. Sabau8), Lance Snead8), Yutai Katoh8), Said I. Abdel-Khalik7)
Takehiko Yokomine1), Yoshio Ueda2), Kazutoshi Tokunaga3), Kazuhisa Yuki4), Masafumi
Akiyoshi5), Shin-ichi Satake6), Kenzo Ibano2), Ken Oohara1), Minami Yoda7)、Adrian S. Sabau8),
Lance Snead8), Yutai Katoh8), Said I. Abdel-Khalik7)
1)京大、2)阪大、3)九大、4)山口東京理科大、5)大阪府大、6)東京理科大、7)Georgia Tech.、8)ORNL1)
Kyoto Univ., 2)Osaka Univ., 3)Kyushu Univ. 4)TUT, Yamaguchi, 5)Osaka Pref. Univ., 6)TUT,
7)
Georgia Tech., 8)ORNL

were performed at H/D less than that of HEMJ
reference design. In the case of H/D = 0.25, thecooling performance increased by ~20% from thevalue for H/D = 0.5 when the jet temperature wasless than 100 o C. By contraries, the cooling
performance was degraded by max. 15% withincrease in jet temperature higher than 200 oC in theH/D = 0.25 case as shown in Fig. 1 (b). The
degraded cooling performance with increasing jet
temperature is attributed to the laminarization due
to highly accelerated flow near cooling surface. Thecooling performance degradation is possible forHeat
Impingement wall
H

62.4

52.3

D (Center hole)
R15
R2.3
φ12.9
φ11.1
φ9.5
φ16.0
φ25.4

[mm]

Fig 1. Cross-sectional view and inner cartridge ofHEMJ test section
H/D0.5 0.25200NuOur task, Task 1 of the PHENIX projectfocuses on characterizing the heat transfer inHe-cooled W armor divertor concepts. The research
objectives of this task are to (1) determine howchanges in material properties due to neutron
irradiation and T retention will affect theperformance and safety margins for PFCs andarmor materials such as W; and (2) establish thethermal-hydraulic performance of such divertor
concepts. The major experimental facilities
involved in this study are the High Heat Flux test
station at the Plasma Arc Lamp facility at ORNL
for measuring the thermal properties of armor
materials, including irradiated specimens, and theHe loop at the Georgia Institute of Technology forheat transfer test for the HEMJ test section shownin Fig. 1. The first 3 years of this task have focusedon understanding heat transfer, due mainly toimpinging-jet cooling using high-temperature andhigh-pressure He gas and high heat fluxes up to 6.6
MW/m2. The latter half of this project will use thisunderstanding, and the numerical models andanalyses developed during the first half, to evaluate
heat transfer through structural materials. The
results from Tasks 2 and 3 regarding how thethermal properties of structural materials areaffected by neutron irradiation, and possibly T
retention, will be used to evaluate how suchchanges affect heat transfer and affect the cooling
performance of He-cooled divertor concepts.
For heat transfer test, the correlation ofNusselt number Nu (heat transfer coefficient) with
the non-dimensional gap width H/D was established
for the design under the condition that H/D was0.4-0.9 and the temperature of He was up to 300 oC.
According to the correlation, removable heat flux
for divertor prototypical conditions was optimized
as 9.4 MW/m2 at He temperature of 700 °C. To
improve the cooling performance, heat transfer tests

15030oC
100ooC
200oC
250oC
300 C

100010000

20000

30000

40000

ReFig 2. Effect of non-dimensional gap width onheat transfer performance of HEMJ

H/D = 0.5 and more wider spacing cases, because
the temperature levels of both cooling surface andcoolant become much higher in an actual divertor.
By changing the jet configuration, the mitigation ofhighly accelerated flow region is required as well as
development of turbulence model to predict thelaminarization.
Assessing the effect of neutron irradiation ofplasma-facing materials has been challenging due
both to technical and radiological challenges. Inan effort to address the radiological challenges, anew high-heat flux facility based on water-wall
Plasma Arc Lamps (PAL) was developed at ORNL.
In the first three years of the PHENIX program, theincident heat flux levels from PAL were limited to3.3 MW/m2. Following a reflector upgrade, theheat flux levels will be increased to 16 MW/m2. As
shown in Figure 1a, the use of PAL allowed the heatsource to be separated from the test chamber,
simplifying the safe testing of low activity level
irradiated articles and materials under high-heat
flux. The enhancement in the radiation safety
during testing of irradiated specimens wasaccomplished by employing an additional, smaller
hemispherical cap chamber, rated for high-vacuum
systems, enclosing the cooling rod, specimen holder,
and irradiated specimen as shown in Fig. 3.
However, the high radioactivity of W and high costof irradiation experiments limit the size of capsules
used in fission test reactors and hence the geometry
and size of neutron-irradiated specimens to several
mm in thickness and less than 1cm in diameter.
We called these specimens, small-and-thin material
specimens (STMS). STMS specimens of vacuum
plasma-sprayed (VPS) tungsten on F82H low
activation steel were tested under high-heat flux
using a PAL facility. Specifically, specimens werebolted onto a refractory metal holder that is attached
to a water-cooled copper alloy rod. The effect ofspecimen bolting on the state of stress anddeformation is not trivial for STMS, as the bolted
area is not directly exposed to high-heat fluxes,
resulting in possible non-uniform temperature
distribution
withinthespecimen.
A
thermo-mechanical model for the simulation of theenergy transport and stress evolution for all thecycles during a HHFT was developed. The
calculated temperatures for the top surface of thespecimens and the back surface of the F82H are
shown in Figure 1c for the first 24 HHF cycles of
10 s duration and absorbed heat fluxes of 1 to 1.41
MW/m2.
Future studies include the evaluation of thethermo-mechanical effects during HHF testing forSTMS. It is very important to quantify the stress

distribution within the specimen during HHF
testing in order to understand the materials science
phenomena leading to changes in material
properties due to HHF exposure. The state ofstress-strain during HHF is also important for
accurate material characterization of exposed
surfaces, such as cracking and/or blistering.
In the remainder of the PHENIX program,neutron-irradiated W/SiC, W, W-K doped, and W-K
doped +3 Re specimens will be tested at HHF of
10-16 MW/m2. The W specimens will have agrain orientation perpendicular or parallel to the topsurface. The properties of specimens will be fully
characterized before and after HHFT in order tounderstand the materials science of the damage
induced by the combined effects of neutron
irradiation and HHF exposure.

(a)

(b)
Fig. 3. Main components of the PAL HHFT: (a)PAL reflector focusing the energy onto the testchamber, (b) setup of main test chamber andspecimen

Fig. 4. Calculated temperatures for a thermal
contact conduction per unit area between the F82Hand Cu washer of 4,000 W/m2K