Prompt -ray Measurement of 35Cl(n,) Using Total Absorption Type Ge Detector

EXPERIMENTS: Samples of 27Al(natural, 0.04g),
35
Cl(CH2-CCl2, 0.008g) and 197Au(natural, 0.02g) were
irradiated by thermal neutrons at the B-4 line. Neutron
flux was 7×105 n/cm/s at the 1MW operation. Measurement times were 1-10 hours. The inset of Fig.1
shows a schematic drawing (side view) of the experiment.
In order to compare the spectrum measured at the center
position with the other one, we measured spectra basedon two sample positions; one is a center position (X=0cm), and the other is a surface position of the detector(X=6.5 cm).
RESULTS AND DISCUSSION: Fig. 1 shows themeasured spectra of 35Cl(n,). Differences between two
spectra are clearly observed in the energy region around
Sn=8.6 MeV. This fact indicates that the probability of
totally absorbed events at X=0 cm is larger than that at
X=6.5 cm. In order to analyze quantitatively, peak areasof the observed intense peaks were compared between
the two spectra. Fig. 2 shows dependence of peakcounts divided by an intensity of -ray (I) [3] as a function of -ray energies. When the peaks are formed by asingle -ray, the values of counts/I are proportional to theefficiency of the detector. Most of the data presented in
the Fig. 2 shows a similar shape with the efficiency of thedetector except for 2468 keV and 8578 keV at X=0 cm.

CONCLUSION: Using the total absorption type Ge
detector, we measured -ray spectrum of 35Cl(n,),27
Al(n,) and 197Au(n,). The peaks of Sn were remarkably enhanced. This measurement method is effective todetect the nuclei of interest by analyze the peak of Sn.
8578 keV(Sn)INTRODUCTION: Prompt -ray analysis (PGAA) is
one of the efficient microanalytical techniques. The
prompt -ray spectrum is composed of many -rays up to
10 MeV. If these -rays were totally absorbed by thedetector, the corresponding event had an energy of Sn(neutron separation energy). When the certain samples
having unknown isotopes were measured with a total
absorption detector, use of the Sn peaks was appropriate
to the analysis. In order to develop a measurement
method by means of a total absorption type Ge detector[1], we used neutron beams of KUR. Our Ge detector
has a through-hole. The samples are put into the center
position of the detector, and neutrons are introduced into
the hole. The capture -rays emitted from the sample
are absorbed by the detector with the large solid angle.
In the previous study, a neutron guide was developed [2].
In the present paper, in order to examine the possibility toapply the method to PGAA, the total absorption spectraof typical nuclei were measured and compared with thegeneral ones.

2468 keV

Institute of Health Biosciences, The University of Tokushima Graduate School
1
Radioisotope Research Center, Nagoya University
2
Research Reactor Institute, Kyoto University

The 8578 keV is Sn of 36Cl, and this peak is formed by
not only a single -ray but also sum of a number of -rays.
Therefore, the 8578 keV data at the X=0 cm shows approximately ten times larger than the other peaks. On
the other hand, the 8578 keV data at the X=6.5 cm did
not show markedly-elevated value. The peak of Sn isenhanced by a factor of ten, therefore we considered thatthe peaks corresponding to the Sn values are available toanalyze a certain sample which consist of the unknown
isotopes. It has possibility that our measurement method can efficiently identify the nuclei of interest comparedto the other measurement method. In order to deducethe detection efficiency of Sn values for various nuclei,
we plan to measure various nuclei.

106

35

Cl(n,)X=0 cm4

BG

X=6.5 cm

10

102
0

5000
10000
Energy [keV]

15000

Fig.1 Measured spectrum of 35Cl(n,). The inset shows across sectional view of the detector. The solid and dashedlines show spectra measured with X=0 cm and X=6.5 cm, respectively.
106
2468 keVPeak Counts/I

H. Hayashi, Y. Kojima1, M. Shibata1 and A. Taniguchi2Counts/Channel

CO2-1

35

Cl(n,)8578 keV
(Sn)

105

4

10

X=0 cm
X=6.5 cm
103

0

2000

4000 6000
Energy [keV]

8000

10000

Fig. 2 Relationship between counts/I and -ray energy. The
peaks of 2468 keV and 8578 keV are formed by sum of thenumber of -rays.

REFERENCES:[1] H. Hayashi et al., Nucl. Instrum. Meth. A 606 (2009)484-489.
[2] H. Hayashi et al., KURRI Prog. Rep. 2010. (2011) 198.
[3] Evaluated Nuclear Structure Data File (ENSDF),
http://www.nndc.bnl.gov/ensdf.

採択課題番号 23020
全吸収検出器を用いた即発ガンマ線強度決定法の開発（徳島大・医）林 裕晃（名大・RIC）小島康明、柴田理尋（京大・原子炉）谷口秋洋

共同通常

CO2-2Development of New Calibration Method for a Neutron Detector using a Pulsed White
Neutron Source from the KURRI-LINAC

T. Matsumoto, H. Harano, A. Masuda, C. Shoda1,
Y. Fukumoto1, J. Kawarabayashi1, H. Tomita1, T. Iguchi1,
A. Uritani1, M. Takada2, S. Kamada2, J. Hori3 and
Y. Sakurai3

counts/neutron.

National Metrology Institute of Japan, National Instituteof Advanced Industrial Science and Technology
1
School of Engineering, Nagoya University
2
National Institute of Radiological Sciences
3
Research Reactor Institute, Kyoto University
INTRODUCTION: Response functions are one of the
key parameters of neutron detectors, which should bedetermined generally by calibration using monoenergetic
neutrons. However, it is difficult to obtain monoenergetic
neutrons in the epi-thermal energy region. In the present study, we have developed a new calibration method
for neutron detectors by means of the time-of-flightmethod using a pulsed white neutron source with energy
range from thermal to 10 keV at KURRI. In this calibration method, a precise detection efficiency curve of
the neutron detector is experimentally determined by
two-dimensional simultaneous measurements of the pulse
height of detector outputs with the time of flight (TOF).
We also developed an epithermal neutron camera consisting of GEMs and resonance filters for neutrons up to
10 keV.
EXPERIMENTS: Neutrons were obtained by thephotoneutron reaction using a water-cooled tantalum target at the KURRI Linac [1]. The neutron spectral
fluence was determined with BGO, 6Li-glass and liquid
scintillators in previous measurements. Calibration tests
were performed for a neutron survey meter “PRESCILA”
composed of plastic scintillators and a ZnS(Ag) scintillator and a personal electric dosimeter composed of Si detectors. The response function of a prototype of epithermal neutron imaging camera was also measured using
the white neutrons. The prototype detector consists of asilver 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
electrode of GEMs between the measurements with andwithout the resonance filter gives the epithermal neutron
image.
RESULTS: Figure1 shows the TOF spectrum measured with the PRESCILA. As shown in Fig.2, the energy response was successfully obtained from the TOF
spectrum and the neutron spectral fluence. The energy
response was obtained also for a personal dosimeter.
Fig.3 show the epithermal neutron image obtained withthe prototype of epithermal neutron imaging camera.
The measured detection efficiency for the epithermal
neutron in the energy range from 4.2 eV to 6.3 eV, corresponding to the resonance peak of 109Ag, was 5x10-4

採択課題番号 23044

Fig. 1 TOF spectrum measured with the PRESCILA

Fig.2 Efficiency curve of the PRESCILA obtained fromthe calibration method with the white neutronsFig.3 Epithermal neutron image obtained by the epithermal neutron imaging camera with GEMs

A part of this study is supported by “Study on a progressive calibration method for neutron dosimeters using
white neutrons” carried out under the Strategic Promotion
Program for Basic Nuclear Research by MEXT,
KAKENHI-Grant-in-Aid for Young Scientists (B)23760825, and JST A-STEP AS231Z02230B.
REFERENCES:[1] 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共同通常
その国際標準化に関する研究（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、照田千尋、福本靖、中山元（放医研）高田真志、鎌田創（京大・原子炉）堀順一、櫻井良憲

CO2-3

Neutron Capture Cross section Measurement on 243Am with a pair of C6D6 detectors

J. Hori, H. Yashima and S. Nakamura1
Research Reactor Institute, Kyoto University
1
Japan Atomic Energy Agency (JAEA)INTRODUCTION: Accurate neutron capture crosssection data of minor actinides (MAs) are required fortransmutation study and design of innovative reactor
system. Americium-243 is one of the most importantMAs since it has a long half-life (7,370 yr) and the neutron capture reaction of 243Am produces higher-mass Cm
isotopes. However, the present status of experimental
data for 243Am is very poor both in quality and quantity.
This is because its highly energetic gamma radiationfrom 239Np (a daughter nuclide of 243Am) causes severe
problems in capture cross-section measurements. Therefore, there are only three available neutron-capture
measurements with the time-of-flight (TOF) method.
Wisshak and Käppeler measured the neutron capture
cross section in the range from 5 to 250 keV using a
Moxon-Rae detector and the 7Li(p,n)7Be neutron source[1]. Weston and Todd measured the neutron capture crosssection in the range from 0.26 to 92 keV using a C6F6detector and the photo-neutron source [2]. Recently, we
have measured the neutron capture cross section of243
Am with a 4 Ge spectrometer in the energy range
from 0.01 to 400 eV at the KURRI-LINAC [3]. In thiswork, we have employed a C6D6 liquid scintillator which
has a fast time response as a prompt gamma-ray detector
in order to obtain the neutron capture cross section in thehigher energy region.
EXPERIMENTS: The capture cross section measurement was carried out by the TOF method using the
KURRI-LINAC. A photo-neutron target of Ta wasadopted as a pulsed neutron source for the neutron TOF
measurement. We employed a pair of C6D6 liquid scintillators for the capture gamma ray measurement. The decay gamma rays from 243Am sample were eliminated bycovering the 6-mm-thick lead shield with the front end ofeach detector. The distance between the sample and theneutron source was 12.0±0.02 m. Output signals from thescintillators were summed up and stored with the Yokogawa’s WE7562 multi channel analyzer as a two dimensional data of pulse height (PH) and TOF.
The americium sample, which was purchased from
Russia Research Institute of Atomic Reactors, was AmO2
powder of 0.128 g packed in an aluminum disk containerof 30 mm in outer-diameter. The amount of 243Am con-tained in the sample was determined as 868±15 MBq bymeasuring the decay gamma rays.
An aluminum disk container without the americium
oxide was used as a dummy sample for the background
determination. An enriched 10B sample was also used tomeasure the incident neutron flux. The sample of 10B was
packed in an aluminum container. The energy dependentneutron flux was derived with the standard cross sectionsof the 10B(n,) reaction. The correction for the neutron
self-shielding and multiple scattering in the sample wasmade by the MCNP-4C [4] with the nuclear data takenfrom JENDL-4.0 [5].
RESULTS: In this experiment, the shape of the 243Am
neutron capture cross section was measured as a functionof neutron energy. The relative yields were normalized at
the 1.356-eV resonance area to the evaluated value in
JENDL-4.0. Making use of a pair of C6D6 liquid scintillators, the neutron capture cross section of 243Am has
been measured up to 40 keV as shown in Fig. 1. Further
study such as application of pulse-height weighting technique will be made to determine absolute cross section
value.

Fig. 1 Neutron capture cross sections of 243Am
This work is supported by JSPS KAKENHI (22226016).
REFERENCES:[1] K. Wisshak and F. Käppeler, Nucl. Sci. Eng., 85, 251(1983).
[2] L. W. Weston and J. H. Todd, Nucl. Sci. Eng., 91, 444(1985).
[3] J. Hori et al., JAEA-Conf 2009-004, 123 (2009).
[4] J. F. Briesmeister, LA-13709-M, Los Alamos National Laboratory (2000).
[5] K. Shibata et al., J. Nucl. Sci. Technol., 48, 1 (2011).

採択課題番号 23048
高速中性子領域における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（原子力機構）中村詔司

共同通常

CO2-4

Reaction Rate Distributions in the Thorium-Loaded Accelerator-Driven System with
14 MeV Neutrons at the Kyoto University Critical Assembly

T. Iwasaki, N. Aizawa, H. Kubo, C.H. Pyeon1, T. Yagi1
and T. Misawa1

10 11 12 13 14 15 16 17 18 19 20
OP

Graduate School of Engineering, Tohoku University
1
Research Reactor Institute, Kyoto University

採択番号 CA23102

TP TP TP TP TP

U

TP TP TP TP TP

V

TP TP TP TP TP

W

TP TP TP TP TP

X

TP TP TP TP TP

Polyethylene

Tritium target

Deuteron beams

Y
Z

Fig. 1 Top view of Th-PE core configuration

Core region

Polyethylene
region
Th-PE

30.0

Th-Gr

3

Reaction rates [1/cm /s/source]

40.0

Th-Be
Th*3-PE

20.0

NU-PE

10.0

0
0

10

20

30

40

Distance from tritium target [cm]Fig. 2 Comparison between the results in experiments of
the 115In(n,)116mIn reaction rate distributions
0.08

Core region

Polyethylene
region0.06

Experiment3

revealed differently the variation of reaction rates at theposition of the tritium target shown Fig. 1. The highest
peak of reaction rates was found in the core region incases of the natural-uranium-polyethylene core (NU-PE
core) shown Fig. 2. The reaction rates in thethorium-graphite (Th-Gr) core were observed flattening in
the entire core region due to the hard neutron spectrum
caused by the graphite, comparing with others. Moreover
the moderation effect of the high-energy neutrons in somecores (Th-PE, Th-Gr and NU-PE cores) was found aroundthe boundary between the core and polyethylene regions.
From these results, the effect of neutron spectrum on theTh capture reactions was observed remarkably in thethorium-loaded ADS experiments with 14 MeV neutrons.
The numerical calculations were executed with the use of
the MCNPX code coupling with ENDF/B-VII.0 and
JENDL-3.3 shown in Fig. 3. The calculated reaction ratesof the Th capture reactions reconstructed approximately
the experimental ones, and the difference between
ENDF/B-VII and JENDL-3.3 libraries was not found in
the reaction rate distributions. Also, another comparison
between the experiments and the calculations
demonstrated good agreement in the thorium-loaded ADS
experiments, including the Th-Be, Th-Th-Th-PE(Th*3-PE; Fig. 2) and NU-PE cores.

T

Reaction rates [1/s/cm /source]

Results and Discussion: The absolute values ofmeasured reaction rates (115In(n,)116mIn reactions)

In wire position

R

Introduction:

The experimental study on theaccelerator-driven system (ADS) in the Kyoto University
Critical Assembly (KUCA) was focused on thedevelopment of a new neutron source. Among a series of
the ADS experiments in KUCA, the experimental resultsof reaction rates of the thorium (Th) capture reactions
were presented: the thorium-loaded ADS experiments
were carried out by varying the neutron spectrum, andwere aimed at measuring the Th capture reactions in thesubcritical system. In the experiments, for theinvestigation of the effect of neutron spectrum, themoderator material was varied in fuel region. The
objectives of this study were to investigate the neutronic
characteristics of the thorium-loaded ADS with 14 MeV
neutrons through the experiments on the reaction rates ofTh capture reactions, and to evaluate the precision of thecalculations by the MCNPX code with ENDF/B-VII.0
and JENDL-3.3 libraries.

TP Thorium fuel and polyethylene

Q

MCNPX (ENDF/B-VII)
MCNPX (JENDL-3.3)

0.04

0.02
Thorium-Polyethylene core

0

0

10

20

30

Distance from the tritium target [cm]Fig. 3 Comparison between the results in experiments andcalculations of the In reaction rate distributions

トリウム燃料装荷加速器駆動システムの基礎実験（東北大学）岩崎智彦、相沢直人、渡辺亮太 （京大原子炉）卞

哲浩、三澤 毅共同通常

40

CO2-5 Measurements of Thorium-Fueled Core Characteristics and Replacement Worth of Thorium
Plates to Aluminum Plates (2)Department of Nuclear Engineering, Tokai University
1
Graduate School of Engineering, Osaka University,
2
Kyoto University Research Reactor Institute
INTRODUCTION: Utilization of Thorium fuel inconventional reactor is known as one alternative approach to diversify fission resource and improve the core
performances. However the accuracy of the cross section
is quietly lower than that of Uranium because there wereless experiments with Thorium and following validation
studies are scarce. This low accuracy brings large uncertainty in calculation results of Thorium-fueled core performance such as k-eff, coefficients, conversion ratio etc..
The object of this experiment is to validate the Thorium
cross section through the comparison of calculation andmeasured results for Thorium-fueled core characteristics
and replacement worth of Thorium plates to Aluminum
plates.
EXPERIMENTS: The assembled core is the first core
to be critical with unit fuel cell named “10/8PETEETEE”
which is shown in Fig. 1.

Poly Poly EU Poly

Th

Poly EU Poly Poly EU Poly

Th

Poly EU Poly Poly EU

Thickness: Poly=1/8inch, EU plate=1/16inch, Th plate=1/8inch
Number density ratio: 232Th/235U=15.2, H/235U= 210

Fig.1.

Unit Fuel Cell(10/8”PETEETEE).

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), and each steps from initial core to
critical core was also analyzed with the comparison of
Uranium-fueled core and the Thorium-fueled core performed with other unit fuel cells. The core arrangements
at each step are illustrated in Fig. 2.

10/8”PETEETEE

Fig. 2. Core arrangements at each step from initial core to
critical core (B10/8”P17ETEETEE).

Initial core were assembled by 29 fuel assemblies marked
as “0” and the number marked in fuel assemblies in Fig.2
shows the fuel assemblies added at each step of critical
approach. The number of fuel assemblies was slightly
increased then the critical core were realized at last step:8
with 47 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).
Control rods arrangement : All rods withdrawn(j=3)

Inverse count rate (Aoj/Aij)

N. Takaki, A. Yamaguchi, H. Watanabe, T. Kitada1, T.
Fujii1, K. Wada1, Vu Thanh Mai1 and H. Unesaki2

Assemblies loaded

Fig.3. Inverse count rate ratio curve obtained for
B10/8”P17ETEETEE core.
The excess reactivity was measured by the period method
and the value is about 0.08%dk/k, and the control rod
worth for C1, C2 and C3 measured by rod drop method
are 0.272, 0.365 and 0.315%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 C3 rod
position at critical with different replacement situation,
because the calibration curve of C3 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 the results are roughly good agreement in the analysis with
continuous energy Monte-Carlo analysis with JENDL4.0.
Table 1. Results of excess reactivity
at each replacement situation.

RESULTS: Thorium-fueled core with H/235U ratio=210
was assembled for the first time and criticality approachand related measurements were successfully performed.
The detailed analysis of the results is in progress.

採択課題番号 CA23105 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 2)
共同通常(東海大工)高木直行、渡辺大貴、山口晃範（阪大院工）北田孝典、藤井貴志、和田憲拓（京大・原子炉）宇根崎博信

CO2-6Development of Subcriticality Measurement for Accelerator-Driven Reactor (VI)

K. Hashimoto, W. Sugiyama, A. Sakon1, M. A.
Binmaarof1, T. Hasegawa1, S. Tanaka1, C. H. Pyeon2,
T. Misawa2 and T. Sano2
Atomic Energy Research Institute, Kinki University
1
Interdisciplinary Graduate School of Science and Technology, Kinki University
2
Research Reactor Institute, Kyoto University
INTRODUCTION: An accelerator-driven subcritical
reactor system has been constructed in A-loading facilityof the KUCA and a series of cross-power spectral analyses between time-sequence signal data from a neutron
detector and a beam current meter have been performed
to develop the methodology of on-line subcriticality
monitoring. The preliminary results of the cross-power
spectrum analyses are showed in this report
EXPERIMENTS: These measurements were performed
in a reactor system referred to as A3/8”P36EU(3). A tritium target was placed outside polyethylene reflector andpulsed neutron beam was emitted from the target. As
pulse repetition frequency, 20, 100 and 500Hz were employed. Not only cross-power spectral density between
time-sequence signal data from two BF3 counters placedin the core, but also the spectral density between the signal data from the neutron counter and a current meter for
accelerator beam were analyzed to determine theprompt-neutron decay constant. The experiments werecarried out in three subcritical states. The subcriticalityof the state was adjusted by changing control rod pattern.
These control rod patterns are showed in Table 1.

( ) A

 02   2
( )   tan1  / 0



,

(1)



(2)

In thisfigure, also, a least-squares fit of the above equation (1) to the point data of delta-function-like peaks is where the other data, i.e., the data of correlated
shown,
reactor noise component are masked. The decay constant
211.3 ± 12.6 (1/s) inferred from the fitting is consistent
with 223.6 ± 5.2 (1/s). obtained by a pulse neutron experiment. The magnitude of the correlated component is
too minute to infer the decay constant.
Figure 2 shows the prompt-neutron decay constantinferred from phase data near the integral multiple ofpulse repetition frequency on the basis of Eq. (2). The
decay constant decreases with an increase in frequency.
In the higher frequency range, the phase analysis underestimates the decay constant. The underestimation originates from unnegligible contribution of spatial higher
mode. However, no least-squares fitting is necessary for
inference of the decay constant and the analysis of phasedata is advantageous than that of magnitude. We should
improve the underestimation in near future.
Pulse Repetition Frequency 20Hz, Rod Pattern A

1E-6

Fitted Curve to Peak Points
1E-8

CPSD
2

[V ]

1E-10

Table 1 Control rod patterns employed
1E-12

1

10
100
Frequency [Hz]1000

Fig.1 Fit to peak points of magnitude data on integral
multiple of pulse repetition frequency
Pulse Repetition Frequency 20Hz, Rod Pattern C

800

RESULTS: Figure 1 shows the magnitude of across-power spectral density measured in a subcriticalsystem (rod pattern A) driven by pulsed neutron source,
whose repetition frequency is 20Hz. The spectral density
consists of a correlated reactor-noise component andmany uncorrelated delta-function-like peaks at integral
multiple of the repetition frequency (20Hz). We formulated the cross-power spectral density between accelerator-beam current and neutron detection signals to obtainthe following formulae for magnitude (gain) and phaseof the imaginary spectral density.

採択課題番号 CA23108

ALPHA-41
ALPHA-42

 [/s] Pulse Neutron Exp.
0
400

0
10

100
Frequency [Hz]1000

Fig.2 Evaluation of prompt-neutron decay constantfrom phase shift data near integral multipleof pulse repetition frequency

加速器駆動未臨界炉における未臨界度測定高度化のための共同通常
基礎実験（Ⅵ）（近大・原研）橋本憲吾、杉山 亘（近大院・理工）左近 敦士、ムハマド・アイマン・ビンマーロ
フ、長谷川 喬、田中慎吾（京大・原子炉）卞 哲浩、三澤 毅、佐野忠史