ABSTRACT To delineate the effect of Radiation Induced Surface Activity (RISA) on boiling phenomenon, surface wettability in high-temperature environment or Leidenfrost condition and critical heat flux (CHF) of oxide metals irradiated by gamma rays were investigated. When the temperature of the heating surface reaches the wetting limit temperature, water-solid contact vanishes because of a stable vapor film between the droplet and the metal surface, i.e., a Leidenfrost condition. The wetting limit temperature increased with integrated irradiation dose. The CHF of oxidized titanium was improved up to 100% after 800 kGy 60 Co gamma ray irradiated. Radiation Induced Boiling Enhancement (RIBE) phenomenon was firstly confirmed through the experiments

Kaichiro Mishima

Koji Okamoto

Tatsuya Koga

Tomoji Takamasa

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Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/27/2019 Terms of Use: Proceedings of ICONE10
International Conference on Nuclear Engineering
Arlington, VA, USA, April 14-18, 2002
Proceedings of ICONE10
10th International Conference on Nuclear Engineering 
Arlington, VA, April 14-18, 2002
 
 
ICONE10-22746
              ICONE10-22746RADIATION INDUCED SURFACE ACTIVITY PHENOMENON 
(2nd report: Radiation Induced Boiling Enhancement) 
 
 
 Tatsuya KOGA,  
Tokyo University of Mercantile Marine,  
2-1-6 Etchujima, Kotoku, Tokyo 135-8533, Japan 
E-mail: tkoga@ipc.tosho-u.ac.jp 
 
Yasuyuki IMAI, 
Tokyo University of Mercantile Marine,  
2-1-6 Etchujima, Kotoku, Tokyo 135-8533, Japan 
E-mail: imai@popnews1.phys.tosho-u.ac.jp 
 
Tomoji TAKAMASA, 
 Faculty of Marine Science,  
Tokyo University of Mercantile Marine 
2-1-6 Etchujima, Kotoku, Tokyo 
135-8533, Japan 
E-mail: takamasa@ipc.tosho-u.ac.jp 
Koji OKAMOTO, 
 Nuclear Engineering Research 
Laboratory, University of Tokyo 
2-22, Shirakata, Tokai-mura, Ibaraki 
319-1106, Japan 
E-mail: okamoto@tokai.t.u-tokyo.ac.jp 
Kaichiro MISHIMA,  
Research Reactor Institute, Kyoto 
University 
Noda, Kumatori, Sennan, Osaka 
590-0494, Japan 
E-mail: mishima@rri.kyoto-u.ac.jp  
ABSTRACT 
To delineate the effect of Radiation Induced Surface 
Activity (RISA) on boiling phenomenon, surface wettability in 
high-temperature environment or Leidenfrost condition and 
critical heat flux (CHF) of oxide metals irradiated by gamma 
rays were investigated. When the temperature of the heating 
surface reaches the wetting limit temperature, water-solid 
contact vanishes because of a stable vapor film between the 
droplet and the metal surface, i.e., a Leidenfrost condition. The 
wetting limit temperature increased with integrated irradiation 
dose. The CHF of oxidized titanium was improved up to 100% 
after 800 kGy 60Co gamma ray irradiated. Radiation Induced 
Boiling Enhancement (RIBE) phenomenon was firstly 
confirmed through the experiments. 
 
Keywords: Radiation Induced Boiling Enhancement (RIBE), Metal 
oxides, Critical heat flux, Leidenfrost condition  
 
INTRODUCTION 
Improving the limit of boiling heat transfer or critical heat 
flux requires that the cooling liquid can contact the heating 
surface, or a high-wettability, highly hydrophilic heating 
surface, even if a vapor bubble layer is generated on the 
surface. From this point of view, investigation on surface 
wettability was performed by use of metal oxides irradiated 
gamma ray. In our previous study, contact angle, an indicator of 
macroscopic wettability, was measured by image processing of 
the images obtained by a CCD video camera. Oxidation on the 
surfaces was carried out by plasma jetting for 40 seconds. The 
results showed that the surface wettability on metal oxide 
pieces of titanium, zircalloy No. 4, SUS-304 and copper 
improved significantly by Radiation Induced Surface Activity (RISA) phenomenon. Highly hydrophilic conditions on the test 
pieces were achieved after 500 kGy irradiation of 60Co gamma 
ray. The contact angle decreased linearly with integrated 
irradiation. The RISA effect was lost, and the wettability 
decreased, after the end of irradiation [1].  
In this study, the wetting limit temperature and life of a 
water droplet on the heated surface of a metal oxide pieces 
were investigated. 
 
EXPERIMENT FOR LEIDENFROST CONDITION 
The experiments were conducted using a lead-bismuth pot 
and a high-speed video camera to check the wettability under 
high-temperature conditions (Fig. 1). Titanium, SUS-304, 
zircalloy No. 4 and copper plates of 20×20 mm in surface area 
and 0.5 mm in thickness were used as the test pieces. Oxidation 
on the surfaces was carried out by plasma jetting for 40 
seconds. An X-ray photoelectron spectroscopy study confirmed 
that a rigid oxide coating, e.g., rutile TiO2 for titanium, exists 
on the metals. The test pieces were irradiated by 60Co gamma 
rays with set radiation intensity and period. Gamma-ray 
facilities in the University of Tokyo and Kyoto University, with 
radiation intensities varing in range of 0.1-20 kGy/hr, were 
used in the experiment. 
Figure 2 shows the phenomena map of the droplet on the 
surface of oxide-titanium before and after 250 kGy irradiation. 
When the surface temperature 360oC, the droplet keeps to be 
spherical and stable film condition is achieved for both before 
and after irradiation conditions. When 300 oC, the droplet on 
the test piece after irradiation loses stable film condition . When 
260 oC, the droplet on irradiated condition splashes into small 
ones and the temperature for irradiated test piece is already  Copyright © 2002 by ASME                                                     Copyright © 200  by ASME 
http://www.asme.org/about-asme/terms-of-use
Downloaunder the limit wetting temperature [2]. When 235 oC, the 
droplet on the irradiated condition contacts the surface and no 
splashes, contrary to non irradiated test piece. The phenomena 
map shows that the criteria temperature or Leidenfrost 
temperature increases about 50 oC after gamma ray irradiation. 
When the temperature of the heating surface reaches the 
wetting limit temperature, water-solid contact vanishes because 
of a stable vapor film between the droplet and the metal 
surface, i.e., a Leidenfrost condition. The wetting limit 
temperature increased with integrated irradiation dose, as 
shown in Fig. 3-4. The temperature decreased after the end of 
irradiation , in the same manner as in the room-temperature 
experiment for contact angle measurements. Observation by 
camera showed the droplet on a gamma-ray irradiated surface 
was more stable than that on a non-irradiated surface. 
 
CRITICAL HEAT FLUX EXPERIMENT 
CHF experiment in the pool boiling condition under the 
atmospheric pressure was carried out for the test section was 0. 
2 mm in thickness, 3 mm in height, and 60 mm in length (Fig. 
5). Oxidation on the surfaces was carried out by plasma jetting 
for 40 seconds. 
Figure 6 shows the critical heat flux of oxide titanium 
against integrated irradiation dose. The results showed that 
CHF of oxidized titanium was improved up to 100% after 800 
kGy 60Co gamma ray irradiated. We call this effect “Radiation 
Induced Boiling Enhancement (RIBE)”. In the figure, K is 
defined as Eq. (1) from interfacial stability analysis conducted 
by Zuber, e.g., K=0.13 is derived [3]. 
 
(1) 
 
Before conducting CHF experiment, contact angles of the 
test pieces were measured to show the relationship between the 
wettability and CHF. As shown in this Fig. 7, CHF in the 
present experiment increases with surface wettability in the 
same manner as Liaw and Dhir’s result [4]. 
 
CONCLUSION 
To delineate the effect of Radiation Induced Surface 
Activity (RISA) on boiling phenomenon, surface wettability in 
high-temperature environment or Leidenfrost condition and 
critical heat flux (CHF) of oxide metals irradiated by gamma 
rays were investigated. When the temperature of the heating 
surface reaches the wetting limit temperature, water-solid 
contact vanishes because of a stable vapor film between the 
droplet and the metal surface, i.e., a Leidenfrost condition. The 
wetting limit temperature increased with integrated irradiation 
dose. The CHF of oxidized titanium was improved up to 100% 
after 800 kGy 60Co gamma ray irradiated. Radiation Induced 
Boiling Enhancement (RIBE) phenomenon was firstly 
confirmed through the experiments. 
( ) 1 42max v lg l v vq h g Kρ σ ρ ρ ρ − = 
 
 Copyright © 2002 by ASME 
 
2
ded From: https://proceedings.asmedigitalcollection.asme.org on 06/27/2019 Terms of UseREFERENCES 
[1] Imai, Y., et al., “Radiation Induced Surface Activity 
Phenomenon”, Proc. of ICONE10, No. 22747 (2002). 
[2] Takata, Y., et al., “Boiling and Evaporation from a 
Superhydrophilic Surface”, Thermal Science and 
Engineering, 8-6 (2000), 33-41. 
[3] Zuber, N., “Hydrodynamic Aspect of Boiling Heat 
Transfer”, Report AECU-4439 (1958). 
[4] Liaw, S. P. and Dhir, V. K., “Effect of Surface Wettability 
on Transitiion Boiling Heat Transfer From a Vertical 
Surface”, Proc. 8th Int. Heat Transfer Conference, vol. 4 
(1986), 2031-2036. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
220
240
260
280
300
320
340
360
 
 
Su
rfa
ce
 T
em
pe
ra
tu
re
, T
W
   
[o C
]
Non irradiated     γ ray irradiated
○ : Stable film boiling
□ : Unstable film boiling
△ : Splash
× : Contact
Fig. 1   Apparatus for Leidenfrost condition 
30
30
Titanium / SUS 304Test piece
Thermocouple
Digital video camera
Micro syringe
HeaterInsulator
Temperature controller
Light
Mirror
Lead/Bismuth
Fig. 2   Phenomena map of Leidenfrost condition (Titanium, 
before and after 250 kGy γ ray irradiation) 2                                                     Copyright © 2002 by ASME 
: http://www.asme.org/about-asme/terms-of-use
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Downloaded  
0ms 
27ms 
54ms 
81ms 
108ms 
Before 
After 1240 kGy γ
ray irradiated 
Titanium 
Fig. 4   Life of droplet on the heated surface 
0 200 400 600 800 1000 1200 1400
260
280
300
320
340
 
 
W
et
tin
g 
Li
m
it 
Te
m
pe
ra
tu
re
, T
W
L  
[o C
]
Integrated Irradiation Dose, X   [kGy]
19.5k Gy/hr γ ray irradiated
   Titanium
   Zircalloy No. 4
Fig. 3   Effect of integrated irradiation dose on wetting limit 
temperature (19.5 kGy/hr)    
 
Copyright © 2002 by ASME 2
 From: https://proceedings.asmedigitalcollection.asme.org on 06/27/2019 Terms of Use 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0 ms 6.7 ms 13 ms 
20 ms 27 ms 33 ms 
Time 
Time 
0 400 800 1200 1600
5.0x105
1.0x106
1.5x106
: Lienhard-Dhir   (Ku = 0.155/Bo1/4)
: Kutateladze   (Ku = 0.16)
H
ea
t F
lu
x,
 q 
   
[W
/m
2 ]
Integrated Irradiation Dose, X   [kGy]
: Critical Heat Flux
Fig. 6   Improvement of CHF by γ ray irradiation (TiO2) 
Fig. 7   Contact angle and CHF 
Fig. 5   Photographs in boiling condition 
Fig. 7   Contact angle and CHF 3                                                     Copyright © 2002 by ASME 
: http://www.asme.org/about-asme/terms-of-use


ICONE10-22746 RADIATION INDUCED SURFACE ACTIVITY PHENOMENON (2nd report: Radiation Induced Boiling Enhancement)

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ICONE10-22746 RADIATION INDUCED SURFACE ACTIVITY PHENOMENON (2nd report: Radiation Induced Boiling Enhancement)

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