CO3-1

Development of In-reactor Observation System Using Cherenkov Light (VII)T. Takeuchi, K. Yamamoto, N. Otsuka, H. Shibata,
H. Nakano, N. Takemoto, K. Tsuchiya, T. Sano1,
H. Unesaki1, Y. Fujihara1, Y. Takahashi1
and K. Nakajima1
Neutron Irradiation and Testing Reactor Center, JAEA
1
Research Reactor Institute, Kyoto University
INTRODUCTION: On-line surveillance system which
can visualize and quantitatively evaluate reactor statuses
will contribute to reactor operation management. Development of an on-line reactor core imaging system using
Cherenkov light was started in 2009. Previously, the total
reactor power of the KUR was successfully estimatedfrom RGB brightness components of the Cherenkov lightat the core using a commercial CCD camera[1]. On theother hand, significant difference of changing rate ofbrightness with total reactor thermal power was observed
between the TC and D2O side of a fuel element[2]. In thisstudy, in order to assess of applicability of Cherenkov
light to acquisition of the reactor thermal power distribution, the image brightness of the Cherenkov light fromseveral fuel elements was compared to the thermal powercalculated by SRAC code system[3].
EXPERIMENTS: The CCD camera (AEC-100ZL, Q·I
Inc.) has been inserted into core-observation pipe of KUR
during increasing the reactor power thermal from 1 to 5
MW. The output of the CCD camera has been collected
as a movie file by a video recorder. Figure 1 shows theCCD camera image of the core of KUR. The Cherenkov
light from the fuel elements of the 3rd to 7th column at
the “Ho” row[4] has been analyzed. Since the G and B
brightness components have caused halation at the higherreactor thermal power than about 1 MW, the R component has been used to correct the total image brightness.

brightness of the Cherenkov light with the thermal power
calculated from the SRAC code system. The comparison
was performed at 1 and 5 MW of the total reactor thermalpower. From the results, for the “Ho”-3, 4, and 5 fuelelements, the thermal power evaluated from Cherenkov
light was almost the same as the one calculated from
SRAC code. On the other hand, for the “Ho”-6 and 7 fuelelements, about 15 % and 35% differences were observed,respectively. The possible causes were that shadow of theequipment around the core and/or anisotropic emission of
Cherenkov light affected on the brightness of the CCD
images. In order to improve the estimation accuracy, installation of a number of cameras at various positions andanalysis of the image brightness with taking account ofemission angle of Cherenkov light.
CONCLUSION: As part of the development of thevisible on-line core surveillance system, the thermal
power estimated by brightness of Cherenkov light wascompared with the one calculated by the SRAC code
system. The results indicate that installation of a numberof cameras at various positions and analysis of the image
brightness with taking account of emission angle of Cherenkov light are required to precisely obtain the distribution of the thermal power by analysis of Cherenkov light.
REFERENCES:[1] N. Ohtsuka, et al., KURRI Progress Report 2013(2015), P. 215.
[2] T. Takeuchi, et al., KURRI Progress Report 2014(2015), P. 108.
[3] K. Okumura, et al., JAEA-Data/Code 2007-004(2007), P. 313.
[4] Kyoto University Research Reactor Institute,
http://www.rri.kyoto-u.ac.jp/KURdiv/info_kur.html.
(in Japanese)

RESULTS: Table 1 shows the comparison of the thermal power of the fuel elements estimated from the“Ho”-3“Ho”-4“Ho”-5“Ho”-6“Ho”-3 “Ho”-4“Ho”-5“Ho”-6 “Ho”-7“Ho”-7

Reactorthermalpower
[MW]
1.0
5.0
1.0
5.0
1.0
5.0
1.0
5.0
1.0
5.0

Thermal power of fuel Cherenkov
element [kW]light
Cherenkov
SRAC
SRAC
light
34.3
35.7
0.96
175.2
178.0
0.98
41.2
40.8
1.01
200.0
203.3
0.98
44.8
41.3
1.09
196.7
205.4
0.96
31.9
38.40.83
164.9
190.8
0.86
21.2
31.1
0.68
100.3
154.6
0.65

Table 1. Comparison of the thermal power of thefuel elements estimated from the brightness of theCherenkov light with the thermal power calculated
from the SRAC code system.

Fig. 1. The CCD camera image of the core of KUR.
The fuel elements of the 3rd to 7th column at the “Ho”
row were indicated by a red box.

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