Radiochemical Measurement of Photonuclear Reaction Yields
for Photon Activation Analysis

Y. Oura, N. Shirai, S. Shibata1 and S. Sekimoto1
Graduate School of Science and Engineering,Tokyo Metropolitan University
1
Research Reactor Institute, Kyoto University
INTRODUCTION:
An instrumental activation
analysis method is one of a nondestructive   and highest
sensitive
method.
Amongactivation
analysis,
instrumental neutron activation analysis (INAA) using (n,γ) reaction are mainly used because it is easy to use
reactor neutons.
Photon activation analysis (PAA) method using (γ, n)reaction by bremsstrahlung from an electron accelerator
is a complementary method to INAA and PAA can determine some elements which INAA can not detemine.
At the present, however, PAA is not used well like NAA.
Main reason of a little use is probably that a machinetime of an electron accelerator is not sufficient for PAA
because an electron accelerator is used by many users ina variety of fields. Furthermore, the other reason isguessed that it is not easy to refer reaction yield values of(γ, n) reactions for calculation of induced radioactivity as
cross section values of (n, γ) reactions. In many
textbooks on photonuclear reaction, a figure of systemtic
relation between reaction yield in mole-1R-1 and target
atomic number by Kato et al. are inserted. But values inmole-1R-1 are practically not easy to calculate induced
activity, therefore values in barn/eq.q. are desired.
In this study a final goal is that absolute reaction yieldvalues in barn/eq.q. of (γ, n) reactions are determined for
usefulness to PAA. Since measurement of absolute fluxof bremsstrahlung is difficult now, relative reaction
yields are determined in the immediate future.
EXPERIMENTS: Target nuclides in this year wereNa, 52Cr, 55Mn, 59Co, 66Zn, 85Rb, 87Rb, 89Y, 127I, 133Cs,
and 197Au, which produce radionuclides with half-life of
more than 1 week by (γ, n) reaction. About 100 mg ofhigh purity powder reagent (metal, oxide, or chloride) is
wrapped in aluminum foil to be formed a disk (8 mmφ) except for Au. For Au, about 12 mg of a foil (8 mm φ)
was used. The disks were placed in a quartz tube together
with Ni monitor foils. Irradiations were performed for 60
min with bremsstrahlung beam of maximun end-point
energy (E0) of 30 MeV from KURRI-LINAC.
After irradiation, a target disk was taken out from aquartz tube and was put into a polyethelne bag.
Gamma-spectrometry by a Ge detector was performed atradioisotpe research facilty, Tokyo Metropolitan
University, after appropriate cooling. To reduce truecoincidence effect a sample was placed at 30 cm far
from a detector.

RESULTS: Relative reaction yields normalized with
one of 58Ni(γ, n)57Ni reaction were obtained. Observed
relative yields (γ, n) reaction at E0 = 30 MeV are shownby closed circles in Fig.1 and relative yields of (γ, 2n)reactions for 58Ni and 85Rb are also shown by open circles. Open triangles present relative yield values of 58Ni(γ,n)57Ni reaction by using Ni powder and the values were1.00 ± 0.06 and 1.01 ± 0.06. These yields confirm that
correct yield values were obtained by using different typeof target and monitor, that is, a powdered target and a Ni
foil monitor in this study.
As shown in Fig.1, relative yields of (γ, n) increasesmoothly with increasing target mass. However, yield of
58
Ni(γ, n) is found to be not consistent with the trend andthe yield value is about 3 times smaller than the trend.
The trend observed in this study can help an estimationof (γ, n) reaction yields for various elements.
Yields of (γ, n) reaction producing a radionuclide withhalf-life of less than 1 week and at E0 = 20 MeV will be
determined in next year.

102

101

Relative Yield

CO2-1

100

10-1

23

10-2

(γ, n)(γ, 2n)

10-3

0

50

100
150
Target Mass

200

250

Fig. 1. Target mass yield for (γ, n) and (γ, 2n) reactions at E0 = 30 MeV. Yield values normalized with ayield of 58Ni(γ, n)57Ni are shown.

光量子放射化分析のための光核反応収率の測定	
 採択課題番号 24071	
 （首都大・理工）大浦泰嗣、白井直樹、和田彩佳	
 （京大・原子炉）柴田誠一、関本俊	
 

共同通常	
 

CO2-2 Precise Measurements for Epi-Thermal Neutrons Using Two Different Scintillators

National Metrology Institute of Japan, National Instituteof Advanced Industrial Science and Technology
1
School of Engineering, Nagoya University
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Evaluation of neutron dose equivalent for the epi-thermal neutron region is very importantin work places with neutron sources or nuclear fuels aswell as irradiation fields in a boron neutron capture therapy. A new calibration method for the response of neutron dosimeters has been developed using a pulse white
neutron beam[1]. On the other hand, it is not easy tomeasure precisely the neutron fluence for epi-thermal
neutrons in an irradiation field, although a gold activation
method is usually used in a thermal neutron region, andan elastic neutron scattering reaction with hydrogen atoms is adopted in a fast neutron region to measure precise neutron fluence. In the present study, we have developed a measurement method for epi-thermal neutrons
using a 6Li6natGd10B3O9:Ce+ (LGB) and an NaI(Tl) scintillators. We also developed an epithermal neutron
camera consisting of GEMs and resonance filters forneutrons up to 10 keV.
EXPERIMENTS: A typical experimental setup is
shown in Fig. 1. A neutron beam through collimators
was obtained by the photoneutron reaction using a water-cooled tantalum target at the KURRI Linac [2]. The
50 mm-diameter and 5-mm thick LGB scintillator was set
at the center of the neutron beam.
The 76.2
mm-diameter and 76.2 mm thick NaI(Tl) was set out ofneutron beam. When the LGB scintillator detects neutrons by the 10B(n,) reaction, 478 keV monoenergetic
gamma rays are produced and subsequently detectedwith the NaI(Tl) scintillator. In the coincidence measurements, the neutron capture reaction rate in the LGB
scintillator is obtained without detection efficiencies of
the LGB and the NaI(Tl) scintillators. Moreover, theabsolute neutron fluence is determined by measuring
gamma rays from the 10B(n,) reaction with the NaI(Tl)scintillator in setting a thick 10B total absorption sample
in front of the LGB scintillator. The detection systemwere experimentally tested using the neutron beam froma neutron source with the photoneutron reaction bymeans of the TOF method. Fig.2 shows the pulse heightspectra of the LGB scintillator with and without the coincidence measurements. In the LGB scintillator, neutrons are detected by the 10B(n,) reaction as well as the6
Li(n,)T reaction and the Gd(n,) reaction. In Fig. 2, apeak around 150 channel is caused by the 10B(n,) reaction. The counts due to the 6Li(n,)T reaction and theGd(n,) reaction are successfully rejected by the coincidence measurements.
Characteristics of a prototype of epithermal neutron
imaging camera were also measured using the TOF
method. The prototype detector consists of a silver
plate as a resonance filter, a B4C thermal neutron absorber, and a GEM with a neutron converter of 10B. The difference in observed counts from each readout electrodeof GEMs between the measurements with and without
the resonance filter gives the epithermal neutron image.

Fig. 1 Typical experimental setup

105

Counts/Channel

T. Matsumoto, H. Harano, A. Masuda, T. Kobayashi, Y.
Yamamoto, H. Tomita, J. Kawarabayashi, T. Iguchi, A.
Uritani, K. Watanabe, J. Hori, Y. Sakurai

10

10

4

B(n,)Without coincidence
measurement
With coincidence
measurement

103
102
101
100

0

1000
Channel2000

Fig.2 Pulse height spectra of the LGB scintillator withand without the coincidence measurements with the
NaI(Tl) scintillator.

REFERENCES:[1] T. Masumoto et al., KEK proc. 2011 (8), 218-225(2012).
[2] K. Kobayashi et al., Annu. Rep. Res. Reactor inst.
Kyoto Univ. 22, 142 (1989).

熱中性子フルエンス率の測定の高度化とその国際標準化に
共同通常
関する研究
（産総研）原野英樹、松本哲郎、増田明彦（名大）井口哲夫、瓜谷章、河原林順、渡辺賢一、
富田英生、小林拓矢、山本洋輔（京大・原子炉）堀順一、櫻井良憲
採択課題番号 24074

Measurements of Neutron Capture Cross Section
for 74Se, 76Se and 77Se at KURRI-LINACINTRODUCTION: Selenium-79 is one of the mostimportant long-lived fission products in the transmutation
study. However, there is no experimental data of neutron-capture cross sections for 79Se because it is difficult
to prepare its sample. Therefore, we have started a systematic measurement of neutron capture cross sections
and gamma-ray spectra of stable Se isotopes in order toimprove the evaluated neutron capture cross sections of
79
Se. In this work, we measured the neutron capture crosssections for 74Se, 76Se and 77Se in the neutron energy
range from 0.01 eV to 10 keV.
EXPERIMENTS: The measurements have been performed by the neutron time-of-flight (TOF) method using
the 46-MeV electron linear accelerator at the Research
Reactor Institute, Kyoto University (KURRI-LINAC).
The neutron capture gamma-rays emitted from sample
were detected by a total absorption spectrometer consisting of twelve Bi4Ge3O12(BGO) scintillators, which wasplaced at a distance of 12.7 m from the photo-neutron
source of the KURRI-LINAC. Since base line fluctuations of signals from the BGO spectrometer were causedby the strong bremsstrahlung (gamma flush) synchronized with the accelerator pulse, a data taking system
based on digital signal processing (DSP) technique was
employed to correct them. A data set of TOF and pulse
height (PH) was obtained by analyzing of waveform of
the signals. Relative cross sections for 74Se, 76Se and 77Se
were obtained from the TOF spectra discriminated by the
PH spectra and the incident neutron flux on the capture
sample determined by the 10B(n, ) standard cross section, and then normalized by the evaluated value of capture cross section at the thermal neutron energy in
JENDL-4.0[1].
RESULTS: Figures 1 to 3 show the neutron capture
cross sections for 74Se, 76Se and 77Se with previous
experimental data and evaluated data[2, 3] in JENDL-4.0,
respectively.
In Fig. 1, present results agree with previous results forkeV neutrons and new resonances of 74Se were found at 6,
123 eV. In Fig. 2, present results are smaller thanprevious results by about 10% for keV neutrons and there
are large difference between present results and thevalues of JENDL-4.0. In Fig. 3, present results are
smaller than previous results by about 10% for keVThis work
JENDL-4.0
Igashira et al.

1000

Cross section[b]Research Reactor Institute, Kyoto University
1
Nuclear Science and Engineering Directorate, Japan
Atomic Energy Agency

10000
neutrons.

100
10
1
0.1
0.01
0.01

0.1

1

10

100

1000

10000

100000

Neutron energy [eV]Fig. 1 Neutron capture cross section for 74Se.
103

This work
JENDL-4.0
Igashira et al.

102

Cross section[b]H. Yashima, J. Hori, Y. Takahashi and S. Nakamura1

101

100

10-1

10-2

10-3
0.01

0.1

1

10

100

1000

10000

100000

Neutron energy [eV]Fig. 2 Neutron capture cross section for 76Se.
1000

This work
JENDL-4.0
KAMADA et al.

100

Cross section[b]

CO2-3

10

1

0.1

0.01
0.01

0.1

1

10

100

1000

10000

100000

Neutron energy [eV]Fig. 3 Neutron capture cross section for 77Se.
This work is supported by JSPS KAKENHI (22226016).
REFERENCES:[1] K. Shibata et al., JENDL-4.0: A New Library for Nuclear
Science and Engineering, J. Nucl. Sci. Technol. 48(1) (2011)
1-30.
[2] M. Igashira et al., Systematic study on keV-neutron capture
reaction of Se isotopes, J. Korean Phys. Soc., 59(2) (2011)1665-1669.
[3] S. Kamada et al.,Measurements of keV-neutron capture
cross sections and capture gamma-ray spectra of 77Se, J. Nucl.
Sci. Technol. 47(7) (2010) 634-641

採択課題番号 24076
Se 安定同位体の中性子捕獲断面積測定に関する研究（京大・原子炉）堀 順一、八島 浩、高橋 佳之（原子力機構）中村 詔司

共同通常Measurement of Gamma Ray and Neutron Spectrum of Curium Isotope

INTRODUCTION:
The yield ratio of higher energy (>3.5MeV) gamma ray
to neutron in a spent fuel pond, (G/N), is linearly related
to the sub-critical multiplication factor ksub [1]. In thepond, (G/N) for ksub=0 is determined by the radioactive
decay of Curium (Cm) isotopes. In order to estimate ksub
by a measurement of (G/N), spectra and intensities of theradiations from the Cm isotopes are essential. However,no data are reported for the gamma ray and only a few
data are done for the neutron [2]. For the reason, measurements of them are launched in KUR-LINAC.
NEUTRON MEASUREMENTS:
The Cm sample was electrodeposited on stainless steel
disk (0.17mm in thickness) and enclosed in a cylindricalfission chamber made of aluminum. The mass ratio of
isotopes, 244Cm / 246Cm / 248Cm = 0.00057 /11.1 / 258. Its neutron source intensity was expected
1.07x104s-1. Neutrons from the sample were measured
with an NE213 scintillator of 5.08cm in thickness and5.08cm in diameter, which is set at 5.2cm from the sample. Pulse heights of the neutrons are calibrated in theelectron light unit with 241Am-Be and 60Co gamma ray
sources. Neutron events counted in the detector wereidentified by the pulse shape discrimination (PSD) technique. Neutrons from a 252Cf source were also measured.
The measured pulse height spectrum for the Cm sample(No-coin.) is found very similar to that of 252Cf as shownin Fig 1. We also performed coincidence measurementsof a fission fragment and a neutron. In the case (coin),count rate of lower energy neutron decreases as shown in
Fig. 1. In the lower energy region, PSD spectra of neutron and gamma ray are slightly overlapped so somegamma ray events are included in the neutron pulse
height spectrum. The decrement of the count rate by thecoincidence might be due to discrimination of lower
energy gamma rays from short lived nuclides generated
by neutron absorptions. To clarify the decrement, a timeof flight measurement of neutron is required.
GAMMA RAY MEASUREMENTS:
In order to measure higher energy gamma rays withhigher efficiency and higher resolution, a BGO scintillator of 7.62cm in diameter and 7.62cm thick and HP-Ge
detector of the 20% relative efficiency were employed.
To reduce direct interactions of neutron in the scitillator,
polyethylene blocks of 25cm thickness was set between
the Cm sample and detectors as shown in Fig. 2. The
gamma ray pulse height spectra in the detectors for theCm sample are also similar to those of 252Cf as shown in
Fig.3. In addition to the 2.2MeV peak of H(n,γ) reaction,
continuum spectra from 3 to 5.5MeV are observed for theCm sample and 252Cf. In the BGO spectra, some bump
structures are found in 6-10MeV region. They might be
attributed to some neutron induced reactions such as
56
Fe(n,γ) in the iron plate or 73Ge(n,γ) in detectors, although peak spectrum is not identified in the HP-Ge. We
shall perform another experiment to identify whether
such bumps are caused by gamma rays directly from thespontaneous fission of the Cm samples or not.
REFERENCES:[1] Y. Nauchi et al., Proc. PHYSOR2012, Oct. 7-10, 2002,
Seoul, 1C-03 on CD-ROM.
[2] EXFOR: Experimental Nuclear Reaction Data,
http://www.oecd-nea.org/dbdata/x4/ on Internet.
Pulse height spectrum (cps/MeV-ee)

Y. Nauchi, J. Hori1 and T. Sano1
Central Research Institute of Electric Power Industry
1
Research Reactor Institute, Kyoto University

103
252

Cf.No-coin
Cm sample, No-coin
Cm sample, coin.with FC

102
101
100
10-1
10-2
10-3
10-4

0

2

4
6
Pulse height (MeV-ee)

810

Fig.1 Neutron pulse height spectrum in NE213 for Cm
sample and 252Cf. Coincidence / No-Coincidence caseswith fission chamber signal.

Fig. 2. Schematic view of gamma ray measurement.
103
Spectrum (cps/MeV)

CO2-4

BGO Cf net
BGO Cm net
HPGe Cf net
HPGe Cm net

102
101
100
10-1
10-2
10-3
0

2

4
6
8
Pulse height (MeV)

10

12

Fig. 3 Gamma ray pulse height spectrum in BGO scintillator for Cm sample and 252Cf.

採択課題番号 24096
キュリウム核種のガンマ線と中性子発生スペクトルの測定(電中研)名内泰志（京大・原子炉）堀順一、佐野忠史

共同通常

Measurements of Thorium-Fueled Core Characteristics and Replacement Worthof Thorium Plates to Aluminum Plates (3)Graduate School of Engineering, Osaka University
Cooperative Major in Nuclear Energy, Tokyo City University
2
Kyoto University Research Reactor Institute1

INTRODUCTION: Thorium is widely known as agood candidate of Uranium, and is considered as a next
generation fuel. However the accuracy of the cross section is quietly lower than that of Uranium because thenumber of experiments with Thorium is not so many andalso validation study is not enough.
The object of this experiment series is to validate theThorium cross section through the comparison between
calculation and measured results for Thorium-fueled corecharacteristics and replacement worth of Thorium plates
to Aluminum plates at various spectrum fields with different unit fuel cell.
EXPERIMENTS: The assembled core is the first core
to be critical with the unit fuel cell named“10/8PETEETEE-r1” which is shown in Fig. 1. This unit
fuel cell is the same composition to the fuel cell named“10/8PETEETEE”, but the difference is in the order of
each plates.

Fig.1 Unit Fuel Cell (10/8”PETEETEE-r1)
In the experiment, critical approach was performed. The
number of fuel assembly and control rod arrangements at
critical were analyzed before the experiment so as tomatch the constraints (maximum excess reactivity andcontrol rod worth). The core arrangements at each step
are illustrated in Fig. 2.
8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

よ
FC#2
FC#1
た
れ
C3
S5
そ
②
つ
N
ね
S4
C1
な
①
ら
む
1 1 1 1 1 1 1
C2 3 2 2 2 3 S6
う
FC#3
UIC#6
5 4 6
ゐ
の
お
UIC#4
く

B10/8"P9ETEETEE-r1

Reflector (Polyethylene)
N

Neutron source

UIC

UIC detector

FC

Fission chamber

C1～C3 Control rod

Initial core were assembled by 36 fuel assemblies, and at
next step fuel assemblies marked as “1” in Fig. 2 wereadded to measure count rate by fission chambers and BF3
detector marked as “①” and “②”. The number of fuelassemblies was gradually increased, and the critical core
were realized at last step:6 with 51 fuel assemblies. The
inverse count rate ratio curve obtained through the critical approach is shown in Fig. 3 for the case of all control
rods withdrawn(j=3).
1.000

Ao/Ai

T. Kitada, T. Fujii, K. Wada, Vu Thanh Mai, N. Takaki1, T.
Katou1 and H. Unesaki2

Inverse Count Rate Ratio

CO2-5

j=3

0.900
0.800
0.700
0.600

BF3#1

0.500

BF3#2

0.400

FC#1

0.300

FC#2

0.200

FC#3

0.100
0.000
36

41

46

51

Number of Fuel Assembly

Fig.3 Inverse count rate ratio curve obtained for
B10/8”P9ETEETEE-r1 core
The excess reactivity was measured by the period method
and the value is about 0.23 [%dk/k], and the control rod
worth for C1, C2 and C3 measured by rod drop method
are 0.260, 0.270 and 0.269 [%dk/k], respectively. These
values satisfy their constraints to operate the core.
The core shown in Fig.2 was slightly changed to low
excess reactivity state so as to measure the replacement
worth. Thorium plates were replaced to Aluminum plates
to measure the replacement worth by the change in excess reactivity. The position of the replacement was thecenter fuel assembly named な 15 and the number of thereplacement was two or four at around the center in coreheight. This measurement was done to check the C1 rod
position at critical with different replacement situation,
because the calibration curve of C1 rod obtained by fitting many experimental results (period method) was confirmed to have enough accuracy to check the excess reactivity. The results are summarized in Table 1, and theresults are roughly good agreement in the analysis with
continuous energy Monte-Carlo code with JENDL-4.0.
Table 1

Measured results of excess reactivity

partialpartial + Al (2)partial + Al (4)excess [Δ k/k]
7.83E-04
2.11E-03
3.34E-03

error [Δ k/k]
3.38E-06
5.83E-06
6.96E-06

S4～S6 Safety rod

Fig. 2 Core arrangements at each step from initial core to
critical core (B10/8”P9ETEETEE-r1)
The number marked in fuel assemblies in Fig.2 shows thefuel assemblies added at each step of critical approach.

RESULTS: Thorium-fueled core which has never assembled at KUCA was assembled. Criticality approachand related measurements were successfully performed.
The detailed analysis of the results is in progress.

採択課題番号CA24105 トリウム燃料炉心の炉心特性およびトリウム置換反応度測定(その 3)（阪大院工）北田孝典、藤井貴志、和田憲拓、Vu Thanh Mai (東京都市大)高木直行、加藤貴士（京大・原子炉）宇根崎博信

共同通常

CO2-6

Measurements of Replacement Worth of Thorium Plates to
Aluminum Plates at EE1 Core
27 cells

1/8"Poly+1/2"Poly×4

EXPERIMENTS: The assembled core named EE1core is the core that the characteristics are already measured. The core arrangement to measure the replacement
worth of Thorium plates is shown in Figure 1.
か
よ
た

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

FC#2

FC#1

F6
S

れ
そ
つ

C3

S5

ね

S4

な
ら

C2

S6

FC#3

UIC#6

の
お

UIC#4

く

28

29

30

31

32

33

34

35

25 cells

1/16"Al
1/16"Al
1/8"Poly

1/16"EU
1/16"EU
1/8"Poly

27

Figure 2(c) Fuel cell arrangement for replacement worth
measurement (Al plates are replaced by Thorium plates)
As shown in Fig.2(c), the replacement positions arearound the central in core height and not adjacent so as toreduce the interference effect in neutron flux caused byThorium plates. The excess reactivity with/without
Thorium plates were measured by checking the C1 rod
position after confirming the accuracy of C1 rod curve by
fitting many experimental results obtained by the period
method. The obtained fitting curve is shown in Figure 3.
fitting curve

0.35%

measured(RunNo=8611)

partial fuel0.30%

measured(RunNo=8614)

0.25%

measured(RunNo=8615-01～03)

0.20%

measured(RunNo=8615-04～07)

B1/8"P60EU-EU fuel( with sample )N

Neutron source

UIC

UIC detector

FC

Fission chamber

む
う
ゐ

26

B1/8"P60EU-EU fuelReflector (Polyethylene)

C1
F6

1/4"Poly+1/2"Poly×5

0.40%

N

S

…

replacement region

excess reactivity [⊿ k/k]

7

27 cells
Upper
Poly

…

Figure 2 (b) Partial fuel assembly (6 fuel cells)
25 cells

INTRODUCTION: Thorium is widely known as agood candidate of Uranium, and is considered as a next
generation fuel. However the accuracy of the cross section is quietly lower than that of Uranium because thenumber of experiments with Thorium is not so many andalso validation study is not enough.
The object of this experiment is to validate the Thorium
cross section through the comparison between calculationand measured results for replacement worth of Thorium
plates to Aluminum plates at various spectrum fields withdifferent unit fuel cell.

1/16"Al
1/16"Al
1/8"Poly

Al baseGraduate School of Engineering, Osaka University
Cooperative Major in Nuclear Energy, Tokyo City University
2
Kyoto University Research Reactor Institute1

6 cells
Lower
Poly

…

1/16"EU
1/16"EU
1/8"Poly

T. Kitada, T. Fujii, K. Wada, Vu Thanh Mai, T. Kojima, T.
Mishiro, N. Takaki1, T. Katou1 and H. Unesaki2

0.15%

0.10%
0.05%
0.00%
650

700

C1～C3 Control rod
S4～S6 Safety rod

Fig. 1. Core arrangement (B1/8”P60EU-EU(5))
The excess reactivity was measured by the period method
and adjusted so as to measure the replacement worth easily by using partial fuel (6 fuel cells) at ら 15. It shouldbe mentioned that the excess reactivity was increasing
during the experiment, therefore the number of the fuelcell at partial fuel was decreased from 6 to 4 at the laterstage of the experiment to satisfy the constraints of KUCA operation.
The fuels are assembled as shown in Figure 2.
60 cells

750
800
C1 rod position [mm]

850

900

Fig. 3. C1 rod curve used for replacement worth measurements
The measured results are summarized in Table 1, andthe results are roughly good agreement in the analysis
with continuous energy Monte-Carlo code withJENDL-4.0.
Table 1. Measured results of excess reactivity
excess [Δ k/k]

error [Δ k/k]

partial_1 + Al (4)3.38E-03

2.9E-06

partial_1 + Th (4)1.16E-03

3.7E-06

partial_2 + Al (4)2.84E-03

1.6E-06

partial_2 + Th (4)5.99E-04

2.0E-06

partial_1 : 6 fuel cells, partial_2 : 4 fuel cells in the partial fuel1/8"Poly+1/2"Poly×4…

1/16"EU
1/16"EU
1/8"Poly

Al base

Lower
Poly

Upper
Poly
1/4"Poly+1/2"Poly×5

Figure 2 (a) Fuel assembly (1/8”P60EU-EU)

RESULTS: The replacement worth of Thorium plates to
Al plates were successfully measured at B1/8”P60EU-EU
core where the neutron spectrum is hard compared to theformer core arrangement(CA2405). The detailed analysis of the results is in progress.

採択課題番号CA24108
EE1炉心におけるトリウム置換反応度測定（阪大院工）北田孝典、藤井貴志、和田憲拓、Vu Thanh Mai、児島達也、三代卓司、(東京都市大)高木直行、加藤貴士、（京大・原子炉）宇根崎博信

共同通常