ISSN 1349-7960

KURRI - TR (CD) - 48

京都大学臨界集合体実験装置におけるトリウム装荷加速器駆動システムの実験ベンチマーク
Experimental Benchmarks on Thorium-Loaded Accelerator-Driven System at
Kyoto University Critical Assembly

編集：卞

哲浩

Edited by : Cheol Ho Pyeon

京 都 大 学 原 子 炉 実 験 所
Research Reactor Institute, Kyoto University

Preface

These experimental benchmarks were contributed to the Collaborative Works(CW) in the International Atomic Energy Agency (IAEA), as entitled “Accelerator
Driven Systems (ADS) Applications and Use of Low-Enriched Uranium in ADS,”
from 2013 to 2014.
The major objective of these benchmarks is to contribute to research anddevelopment of ADS through the thorium (Th)-loaded ADS experimental data withthe use of 14 MeV neutrons and spallation neutrons generated by 100 MeV protons
and tungsten target carried out at the Kyoto University Critical Assembly (KUCA)
A-core.
Special thanks are due the KUCA and the fixed-filed alternative gradient (FFAG)
accelerator staff and students for support and patience throughout a series of
Th-loaded ADS experiments carried out at KUCA.

Cheol Ho Pyeon
January 2015

Keywords:
Th-ADS, KUCA, FFAG accelerator, 14 MeV neutrons, Spallation neutrons

｢i｣

要

旨

この実験ベンチマーク問題は、国際原子力機関（IAEA）において 2013 年から 2014年にかけて行われた国際共同作業プロジェクト「加速器駆動システムの応用と低濃縮
ウラニウムの利用」の一部として採択された「京都大学臨界集合体実験装置におけるトリウム装荷加速器駆動システムの実験ベンチマーク」である。
この実験ベンチマーク問題は、
KUCA の A 架台において行われた 14 MeV 中性子（パルス中性子発生装置）および FFAG 加速器から得られる核破砕中性子を用いた実験を通して、ADS の基礎研究の発展に貢献することを目的としている。
最後に、KUCA においてトリウム装荷 ADS 実験を準備および運転にご協力をいた
だいた KUCA および FFAG 加速器のスタッフ、実験における測定および数値解析に献身的に取り組んだ KUCA 棟に在籍していた学生諸君に心から感謝の意を表します。

卞 哲浩
2015 年 1 月｢ii｣Contents

Experimental Benchmarks on Thorium-Loaded Accelerator-Driven System at
Kyoto University Critical Assembly
1. Collaborative Work Specifications ･･････････････････････････････････････････････ 2
1-1

Introduction ････････････････････････････････････････････････････････････ 2

1-2

Experimental Settings ････････････････････････････････････････････････････ 3

1-3

Experimental Results ･････････････････････････････････････････････････････ 4

1-4

References ･･････････････････････････････････････････････････････････････ 5

Appendix ････････････････････････････････････････････････････････････････････ 7

2. Core Configurations ･････････････････････････････････････････････････････････ 19
3. Results of ADS Experiments ･･････････････････････････････････････････････････ 22
3-1

Thorium plate irradiation experiment ･･････････････････････････････････････ 22

3-2

Reaction rate distribution ････････････････････････････････････････････････ 24

3-3Time evolution data of PNS and Noise methods ･････････････････････････････ 26

｢iii｣

目

次

京都大学臨界集合体実験装置でのトリウム装荷加速器駆動システムの実験ベンチマーク
1. 実験ベンチマーク･････････････････････････････････････････････････････････････ 2
1-1

はじめに････････････････････････････････････････････････････････････････ 2

1-2

実験条件････････････････････････････････････････････････････････････････ 3

1-3

実験結果････････････････････････････････････････････････････････････････ 4

1-4

参考文献････････････････････････････････････････････････････････････････ 5

付録 ････････････････････････････････････････････････････････････････････････ 7

2. 炉心構成････････････････････････････････････････････････････････････････････ 19
3. トリウム装荷 ADS 実験の結果･････････････････････････････････････････････････ 22
3-1 トリウム板照射実験･･･････････････････････････････････････････････････････ 223-2反応率分布･･････････････････････････････････････････････････････････････ 24

3-3 パルス中性子法およびノイズ法の時系列データ････････････････････････････････ 26｢iv｣

Experimental Benchmarks on
Thorium-Loaded Accelerator-Driven System at
Kyoto University Critical Assembly

Research Reactor Institute, Kyoto University, Japan
Cheol Ho Pyeon
5th January, 2015

1

1. Collaborative Work Specifications
1-1. Introduction
The accelerator-driven system (ADS) was developed for producing energy and for transmuting
minor actinides and long-lived fission products. ADS has attracted worldwide attention in recent years
because of its superior safety characteristics and potential for burning plutonium and nuclear waste. An
outstanding advantage of its use is the anticipated absence of reactivity accidents, provided sufficient
subcriticality is ensured.

At the Kyoto University Research Reactor Institute [1]-[2], a series ofexperiments for ADS was launched in fiscal 2003 at the Kyoto University Critical Assembly (KUCA)[3]-[19], with sights on a future plan (Kumatori Accelerator Driven Reactor Test Facility & Innovation
Research Laboratory: Kart & Lab. Project). A new accelerator was attached to the KUCA facility in
March 2008, and the high-energy neutrons generated by the interaction of 100 MeV protons withtungsten target was injected into KUCA. The new accelerator is called the fixed-field alternating
gradient (FFAG) accelerator of the synchrotron type developed by High Energy Accelerator Research
Organization (KEK) in Japan.
At KUCA, by combining a critical assembly of a solid-moderated and -reflected type core with theaccelerators, 14 MeV pulsed neutrons generated by D-T (deuteron–tritium) reactions and 100 MeV
protons generated from the FFAG accelerator were injected separately into the subcritical system, where
the highly-enriched uranium (HEU), thorium (Th) and natural uranium (NU) fuel was loaded together
with the reflectors, including the polyethylene (PE), graphite (Gr) and beryllium (Be). The experimentsof thorium-loaded ADS were carried out by varying the neutron spectrum and the external neutron
source, and were aimed at investigating the sensitivity of thermal neutron flux for thorium capture
reactions, and the prompt and delayed neutron behaviors in the subcritical system. The thorium-loaded
ADS experiments provided importantly the effects of the neutron spectrum and the external neutron
source on both the static and kinetic parameters. In the experiments, for the investigation of the effectof neutron spectrum, the moderator material was varied in fuel region. As the other investigation of theeffect, the external neutron source (14 MeV neutrons and 100 MeV protons) was injected separately into
the thorium-loaded core varying the moderator. Before the subcritical experiments, the thorium plateirradiation experiment was carried out in the KUCA core, to analyze experimentally the thorium capture
and fission reactions in the critical system as the reference of subcritical system, although the probabilityof 232Th capture and 233U fission reactions could be examined in the subcritical state.
The objectives of this study were to investigate the neutronic characteristics of the thorium-loaded
ADS with external neutron source through the static and kinetic experiments, and to evaluate theaccuracy of the Monte Carlo analyses through the calculations by the MCNPX [20] code with
ENDF/B-VII.0 [21], JENDL/HE-2007 [22]-[23] and JENDL/D-99 [24] libraries.

21-2. Experimental Settings
1-2-1. Description of KUCA core
KUCA comprises solid-moderated and -reflected type-A and -B cores, and a water-moderated and-reflected type-C core. In the present series of experiments, the solid-moderated and -reflected type-A
core was combined with a Cockcroft-Walton type pulsed neutron generator and the FFAG accelerator at
KUCA.
The A-core (A3/8”P36EU(3)) configuration used for measuring the reaction rates of thorium metal
plate is shown in Fig. 1-1. The fuel rods were constructed of a combination of 21 elements that were
loaded on the grid plate. The materials used in the critical assemblies were always in the form ofrectangular parallelepipe, 2” sq. with thickness ranging between 1/16” and 2”. The upper and lower
parts of the fuel region were polyethylene reflector layers of more than 500 mm long, as shown in Fig.
1-2.

The fuel rod, a 93% enriched uranium-aluminum (U-Al) alloy, consisted of 36 cells of 2

polyethylene plates 1/8” and 1/4” thick, and a U-Al plate 1/16” thick and 2” sq. The functional heightof the core was approximately 400 mm.
1-2-2. Description of 14 MeV Pulsed neutron generator
The pulsed neutron generator was combined with the KUCA A-core, where 14 MeV pulsed
neutrons were injected into the subcritical system. In the experiments, the deuteron beams were led tothe tritium (3H; T) target located outside the polyethylene reflector. At the pulsed neutron generator, thebeam peak characteristics are about 0.5 mA intensity, 10 μs pulsed width, 100 Hz pulsed frequency, 25
mm diameter spot size and 1×107 1/s neutron yield.
1-2-3. Description of FFAG accelerator
100 MeV protons generated from the FFAG accelerator were injected onto the tungsten target. The
main characteristics are under the following parameters: 100 MeV energy, 0.3 nA intensity, 20 Hz pulsed
frequency, 100 ns pulsed width and 40 mm diameter spot size at the tungsten target (50 mm diameter and
9 mm thick). The thickness of target was determined on the basis of previous analyses [11], [18] in thereaction rates for high-energy protons. A level of the neutron yield generated at the target was around
1.0×107 1/s by an injection of 100 MeV protons onto the tungsten target.

31-3. Experimental Results
1-3-1. Indium (In) reaction rate distribution (Th-loaded ADS experiments)
Indium (In) wire 1.5 mm diameter and 600 mm long was set in the axial center position along (16,17-Q, Y; 14 MeV neutrons) and (13, 14-I, A’; 100 MeV protons) the vertical shown in Figs. 2-1, 2-2, 2-3
and 2-4 for measuring the reaction rate distribution. The experimental results of the In wire wereobtained by measuring total counts of the peak energy of γ-ray emittance and normalized by the countsof irradiated Nb (10×10×1 mm) and In foils (10×10×1 mm) emitted from 93Nb(n, 2n)94Nb (thresholdenergy 9 MeV) and 115In(n, n’)115mIn (threshold energy 0.3 MeV) reactions set in the location of thetritium and tungsten targets, respectively.
1-3-2. Time evolution data of PNS and Noise methods (Th-loaded ADS experiments)
For 14 MeV neutrons, to monitor carefully the prompt and delayed neutron behaviors, each core
was set with three 3He detectors (20 mm diameter and 300 mm long) at the positions of #1 at (12, X),#2 at (15, R) and #3 at (18, R) (Fig. 2-1 for Th-PE, Th-Gr, Th-Be, Th-HEU-PE and NU-PE cores), and#1 at (12, R) and #2 at (15, R) (Fig. 2-3 for Th-HEU-5PE and Th-HEU-Gr-PE cores).

Through thetime evolution of the prompt and delayed neutrons, the prompt neutron decay constant was deduced by
the least-square fitting of the time evolution of the neutrons to an exponential function over the time
optimal duration.

Subcriticality was deduced by the extrapolated area ratio method on the basis of

the prompt and delayed neutron behaviors. For 100 MeV protons, neutron detectors (3He detectors; #1,#2 and #3) were set at three positions shown in Fig. 2-2 for Th-PE, Th-Gr, Th-Be, Th-HEU-PE and
NU-PE cores: #1 at (18, A), #2 at (15, H) and #3 at (12, H)), and Fig. 2-4 for Th-HEU-5PE and
Th-HEU-Gr-PE cores: #1 at (18, H) and #2 at (15, H).
1-3-3. Critical position and Excess reactivity (Th plate irradiation experiment)
The critical state was adjusted by maintaining the control rods in certain positions, and the excess
reactivity was attained on the basis of its integral calibration curve obtained by the positive period
method.

4

1-4. References[1]

S. Shiroya, H. Unesaki, Y. Kawase, H. Moriyama and M. Inoue, “Accelerator Driven Subcritical
System as a Future Neutron Source in Kyoto University Research Reactor Institute (KURRI) –Basic Study on Neutron Multiplication in the Accelerator Driven Subcritical Reactor,” Prog.
Nucl. Energy, 37, 357 (2000).

[2]

S. Shiroya, A. Yamamoto, K. Shin, T. Ikeda, S. Nakano and H. Unesaki, “Basic Study on
Accelerator Driven Subcritical Reactor in Kyoto University Research Reactor Institute(KURRI),” Prog. Nucl. Energy, 40, 489 (2002).

[3]

C. H. Pyeon, Y. Hirano, T. Misawa, H. Unesaki, C. Ichihara, T. Iwasaki and S. Shiroya,“Preliminary Experiments on Accelerator Driven Subcritical Reactor with Pulsed Neutron
Generator in Kyoto University Critical Assembly,” J. Nucl. Sci. Technol., 44, 1368 (2007).

[4]

C. H. Pyeon, M. Hervault, T. Misawa, H. Unesaki, T. Iwasaki and S. Shiroya, “Static and Kinetic
Experiments on Accelerator Driven Subcritical Reactor with 14 MeV Neutrons in Kyoto
University Critical Assembly,” J. Nucl. Sci. Technol., 45, 1171 (2008).

[5]

C. H. Pyeon, H. Shiga, T. Misawa, T. Iwasaki and S. Shiroya, “Reaction Rate Analyses for an
Accelerator-Driven System with 14 MeV Neutrons in Kyoto University Critical Assembly,” J.
Nucl. Sci. Technol., 46, 965 (2009).

[6]

C. H. Pyeon, T. Misawa, J. Y. Lim et al., “First Injection of Spallation Neutrons Generated by
High-Energy Protons into the Kyoto University Critical Assembly,” J. Nucl. Sci. Technol., 46,
1091 (2009).

[7]

H. Shahbunder, C. H. Pyeon, T. Misawa and S. Shiroya, “Experimental Analysis for Neutron
Multiplication by using Reaction Rate Distribution in Accelerator-Driven System,” Ann. Nucl.
Energy, 37, 592 (2010).

[8]

H. Taninaka, K. Hashimoto, C. H. Pyeon, T. Sano, T. Misawa and T. Osawa, “Determination ofLambda-Mode Eigenvalue Separation of a Thermal Accelerator-Driven System from Pulsed
Neutron Experiment,” J. Nucl. Sci. Technol., 47, 376 (2010).

[9]

H. Shahbunder, C. H. Pyeon, T. Misawa, J. Y. Lim and S. Shiroya, “Subcritical Multiplication
Factor and Source Efficiency in Accelerator-Driven System,” Ann. Nucl. Energy, 37, 1214
(2010).

[10]

H. Shahbunder, C. H. Pyeon, T. Misawa, J. Y. Lim and S. Shiroya, “Effects of Neutron Spectrum
and External Neutron Source on Neutron Multiplication Parameters in Accelerator-Driven
System,” Ann. Nucl. Energy, 37, 1785 (2010).

[11]

C. H. Pyeon, H. Shiga, K. Abe, H. Yashima, T. Nishio, T. Misawa, T. Iwasaki and S. Shiroya,“Reaction Rate Analysis of Nuclear Spallation Reactions Generated by 150, 190 and 235 MeV
Protons,” J. Nucl. Sci. Technol., 47, 1090 (2010).

[12]

H. Taninaka, K. Hashimoto, C. H. Pyeon, T. Sano, T. Misawa, H. Unesaki, W. Sugiyama and T.
Osawa, “Determination of Subcritical Reactivity of a Thermal Accelerator-Driven System fromBeam Trip and Restart Experiment,” J. Nucl. Sci. Technol., 48, 873 (2011).

[13]

C. H. Pyeon, J. Y. Lim, Y. Takemoto, T. Yagi, T. Azuma, H. S. Kim, Y. Takahashi, T. Misawa and5

S. Shiroya, “Preliminary Study on the Thorium-Loaded Accelerator-Driven System with 100
MeV Protons at the Kyoto University Critical Assembly,” Ann. Nucl. Energy, 38, 2298 (2011).

[14]

H. Taninaka, A. Miyoshi, K. Hashimoto, C. H. Pyeon, T. Sano, T. Misawa, W. Sugiyama and T.
Osawa, “Feynman-α Analysis for a Thermal Subcritical Reactor System Driven by an Unstable
14MeV-Neutron Source,” J. Nucl. Sci. Technol., 48, 1272 (2011).

[15]

C. H. Pyeon, Y. Takemoto, T. Yagi, Y. Takahashi and T. Misawa, “Accuracy of Reaction Rates in
the Accelerator-Driven System with 14 MeV Neutrons at the Kyoto University Critical
Assembly,” Ann. Nucl. Energy, 40, 229 (2012).

[16]

J. Y. Lim, C. H. Pyeon, T. Yagi and T. Misawa, “Subcritical Multiplication Parameters of the
Accelerator-Driven System with 100 MeV Protons at the Kyoto University Critical Assembly,”
Sci. Technol. Nucl. Install., 2012, ID: 395878, 9 pages, (2012).

[17]

Y. Takahashi, T. Azuma, T. Nishio, T. Yagi, C. H. Pyeon and T. Misawa, “Conceptual Design ofMulti-Targets for Accelerator-Driven System Experiments with 100 MeV Protons,” Ann.
Nucl. Energy, 54, 162 (2013).

[18]

C. H. Pyeon, T. Azuma, Y. Takemoto, T. Yagi and T. Misawa, “Experimental Analyses ofExternal Neutron Source Generated by 100 MeV Protons at the Kyoto University Critical
Assembly,” Nucl. Eng. Technol., 45, 81 (2013).

[19]

A. Sakon, K. Hashimoto, W. Sugiyama, H. Taninaka, C. H. Pyeon, T. Sano, T. Misawa, H.
Unesaki and T. Ohsawa, “Power Spectral Analysis for a Thermal Subcritical Reactor System
Driven by a Pulsed 14 MeV Neutron Source,” J. Nucl. Sci. Technol., (2013). [in print][20]

D. B. Pelowitz, “MCNPX User’s Manual, Version 2.5.0.,” LA-CP-05-0369, (2005). Los Alamos
National Laboratory.

[21]

M. B. Chadwick, P. Oblozinsky, M. Herman et al., “ENDF/B-VII.0: Next Generation EvaluatedNuclear Data Library for Nuclear Science and Technology,” Nucl. Data Sheets, 107, 2931
(2006).

[22][23]

T. Fukahori, “JENDL high-energy file,” J. Nucl. Sci. Technol., suppl., 2, 25 (2002).
H. Takada, K. Kosako and T. Fukahori, “Validation of JENDL High-Energy File throughAnalyses of Spallation Experiments at Incident Proton Energies from 0.5 to 2.83 GeV,” J. Nucl.
Sci. Technol., 46, 589 (2009).

[24]

K. Kobayashi, T. Iguchi, S. Iwasaki et al., “JENDL Dosimetry File 99 (JENDL/D-99),” JAERI
Report 1344, (2002).

6

Appendix
1

2

3

4

5

6

7

8

9

10 11 12 13

14 15 16

17 18 19 20 21 22

23 24 25 26 27 28A
B

F

Fuel (3/8"P36EU)

18

Partial fuel (3/8"P18EU)

UT

EU+Th fuel (3/8"P35EU+Th)

D
E

FC#3

UIC#4

G
H
I
J

Polyethylene reflector

K

FC#2

C3

L
M

S4

O
P

UIC#5

F

F

F

F

F

F

F

F

F

F

F

F

UT

F

F

F

F

F

F

F

C2

Q

18

FC#1

S5

Aluminum sheath

C1

C

Control rod

S

Safety rod

N

Neutron source (Am-Be)

FC

Fission chamber

FC
UIC

UIC detector

N
S6

R
T
U
V
W
X

UIC#6

Y
Attachment of gold foils

Z

Fig. 1-1 The general view of KUCA core configuration

Void
betweenassemblies

Polyethylene
587 mmAluminum
sheathFuel50.8 mm
Fuel(36 cells )400 mm1524 mm

51.3 mm
54.3 mmPolyethylene
528mm

55.3 mmFig. 1-2 Description of fuel assembly at KUCA

7Internal void

Fuel plate

Polyethylene plate

Fig. 1-3 Description of fuel (HEU, Th and NU) and polyethylene plates

Unit cell(11.11 mm)

1/16”EU(1.59 mm)Polyethylene (PE)(19”+1/2*2;
508.00 mm)

Polyethylene (PE)(19”; 482.60 mm)

20 mm Al plate(20.00 mm)

1/2”PE×2(25.40 mm)

1/8”PE+1/4”PE(3.18+6.35) mm

Reflector 528.00 mm(Lower)Fuel 399.96 mm(Unit cell 36 times)

1/2”PE×5+1/8”PE×5(79.38 mm)

Reflector 587.38 mm(Upper)Fig. 1-4 Fall sideways view of fuel assembly “F” shown in Fig. 1-1

1/16”EU(1.59 mm)

Al cell
9 times

20 mm Al+1/2”PE×2(45.40 mm)

Unit cell(11.11 mm)

Polyethylene(PE)(19”; 482.60
mm)

Al cell (11.11 mm)(1/16”Al+1/8”PE+1/4”PE)
Reflector 627.99 mm(Lower)Polyethylene(PE)(19”+1/2”*2;
508.00 mm)

1/8”PE+1/4”PE(3.18+6.35) mm

Fuel 199.98 mm(Unit cell 18 times)

Al cell
9 times

1/2”PE×5+1/8”PE×5(79.38 mm)

Reflector 686.55 mm(Upper)Fig. 1-5 Fall sideways view of partial fuel assembly “18” shown in Fig. 1-1

8

(1/16”EU+1/8”PE+1/4”PE)×18(Unit cell 18 times; 199.98 mm)(1/16”EU+1/8”Th+1/4”PE)(11.11 mm)

Polyethylene (PE)(19”+1/2”*2;
508.00 mm)

Polyethylene (PE)(19”; 482.60 mm)

20 mm Al+1/2”PE×2(45.40 mm)(1/16”EU+1/8”PE+1/4”PE)×17(Unit cell 17 times; 188.87 mm)

Reflector 528.00 mm(Lower)Fuel 399.96 mm(Unit cell 35 times+EUTh fuel)1/2”PE×5+1/8”PE×5(79.38 mm)

Reflector 587.38 mm(Upper)Fig. 1-6 Fall sideways view of partial fuel assembly “UT” shown in Fig. 1-1

Voidbetweenassemblies
Aluminum
sheathPolyethylene(Aluminum)

Polyethylene(Aluminum)
50.8 mm

1524 mmInternal void51.3 mm
54.3 mm55.3 mmFig. 1-7 Description of polyethylene reflector at KUCA

9

Anhydrous
Boron
Void
betweenassemblies
Aluminum
sheathInternal void1470 mm

1524 mmAnhydrous
Boron

Aluminum
sheath33.8 mm40.0 mm
45.0 mm50.0 mm55.3 mmFig. 1-8 Description of control (safety) rod at KUCA

Polyethylene
50.8 mmPolyethylene
50.8 mmPolyethylene
50.8 mm

Fuel50.8 mm

Fuel50.8 mm

Fuel50.8 mm

Fuel50.8 mm

Fuel50.8 mm

Fuel50.8 mmPolyethylene
50.8 mm

1 mm gap

3 mm gap

FC#3

UIC#4

1 mm gap

FC#2

C3

S4
UIC#5

Polyethylene
50.8 mm

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

C2

F

F
F

S5

3 mm gap

1 mm gap

FC#1

C1
N

S6

Fig. 1-9 Description of fuel assembly, polyethylene reflector and control rod at KUCA

10

Indium (In) wireInternal void

Aluminum sheath

Target

1.5 mm
2.0 mm
2.2 mmFuel assembly baseFig. 1-10 Setting of Indium (In) wireFe
Al

Control orsafety rod

B2O3

Al
Shock absorber

20 mm
35 mm

Measuredrod length1470 mm

Actualrod length

5 mm
92.5 mm

Fuel assembly baseFig. 1-11 Actual position of control (safety) rod(Actual position = Measured position – 97.5 mm)

11Nb foil(10*10*1
mm3)1524 mm(14, X)(15, X)

735 mm(14, X) (15, X)

Fig. 1-12 Nb foil attachment near the tritium target in Thorium-loaded ADS with 14 MeV neutrons

Targetlocation

In wire position

3H target: 735 mm
W target: 700 mm

Fuel assembly base3

H target: 20 + 55.3*11 mm = 628.3 mm
W target: 75 + 55.3*11 mm = 683.3 mm

Fig. 1-13 Side view of target and core configuration with 14 MeV neutrons (3H; T target) or 100 MeV
protons (tungsten; W target)12

50 mm (lower side)

50 mm (upper side)

Gold foil sandwichedby two Cd covers
Cd cover:10 mm diam.
1 mm thick

54.3 mm

Gold foil (Bare)
8 mm diam.
0.05 mm thickGold foil (Cd covers)
8 mm diam.
0.05 mm thickThorium plate(2”×2”×1/8”; (15, O) in Fig. 1-12)

Fig. 1-14 Fall sideways view of UT fuel rod in (15, O; Fig. 1-1)

80 mm

3 mm

50 mm

3 mm

100 mm

48 mm

Proton beams (40 mm diameter)

W target(50 mm diameter
9 mm thick)Enlarged (target location)
1 mm
In foil(10*10*1 mm3)

9 mm
3 mm

10 mm

W target(50 mm diameter
9 mm thick)

50 mm

10 mm
50 mm

Fig. 1-15 Tungsten target configuration of thorium-loaded ADS experiments with 100 MeV
protons (Note that W target was 50 mm diameter and 12 mm thick in the Th-HEU-5PE and
Th-HEU-Gr-PE cores.)13

1/8”Th (1/8”NU)(3.18 mm)
Al plate (20.00 mm)

Unit cell(15.88 mm)

Polyethylene (PE)(19”+1/2*11;622.30 mm)

Polyethylene (PE)(19”+1/2*8+1/4”;
590.55 mm)

1/2”PE (1/2”Gr; 1/2”Be)(12.70) mm
Reflector 610.55 mm(Lower)Fuel 254.08 mm(Unit cell 16 times)

Reflector 622.30 mm(Upper)Fig. 1-16 Fall sideways view of fuel assembly Th-PE, Th-Gr, Th-Be and NU-PE
1/8”Th(3.18 mm)

Unit cell(14.29 mm)

1/16”EU(1.59 mm)

Al plate (20.00 mm)

Polyethylene (PE)(19”+1/2”*11;622.30 mm)

Polyethylene (PE)(19”+1/2”*9+1/4”;
603.25 mm)

1/8”PE+1/4”PE(9.52 mm)
Reflector 623.25 mm(Lower)Fuel 228.64 mm(Unit cell 16 times)

Reflector 622.30 mm(Upper)Fig. 1-17 Fall sideways view of fuel assembly Th-HEU-PE
Unit cell(1/8”Th+5*(1/16”HEU+1/8”PE+1/4”PE))(58.73 mm)
1/8”Th(3.18 mm)1/16”EU(1.59 mm)

Al plate (20.00 mm)

Polyethylene (PE)(19”+1/2”*12+1/8”;
638.18 mm)

Polyethylene (PE)(19”+1/2”*9+1/4”;
603.25 mm)

1/8”PE+1/4”PE(9.52 mm)
Reflector 623.25 mm(Lower)Fuel 234.95 mm(Unit cell 4 times)

Reflector 638.18 mm(Upper)Fig. 1-18 Fall sideways view of fuel assembly Th-HEU-5PE

14

Unit cell
(1/8”Th+4*(1/16”HEU+1/2”Gr)+1/8”PE)(63.50 mm)
1/8”Th(3.18 mm)1/16”EU(1.59 mm)1/8”PE(3.18 mm)

Al plate (20.00 mm)

Polyethylene (PE)(19”+1/2”*8+1/4”;
590.55 mm)

Polyethylene (PE)(19”+1/2”*11;622.30 mm)

1/2”Gr
(9.52 mm)
Reflector 610.55 mm(Lower)Fuel 254.00 mm(Unit cell 4 times)

Reflector 622.30 mm(Upper)Fig. 1-19 Fall sideways view of fuel assembly Th-HEU-Gr-PE

15

Table 1-1 Atomic densities of 1/16” thick highly-enriched uranium (HEU) fuel plate (U-Al alloy)
Atomic density

Isotope(×1024/cm3)

235

1.50694×10-3

238

U

1.08560×10-4

Al

5.56436×10-2

U

Table 1-2 Atomic densities of 1/8” thick thorium (Th) fuel plate
Atomic density

Isotope(×1024/cm3)232

2.86389×10-2

Th

Table 1-3 Atomic densities of 1/8” thick natural uranium (NU) fuel plate
Atomic density

Isotope(×1024/cm3)235

3.25792×10-4238

4.48577×10-2

U
U

Table 1-4 Atomic densities of polyethylene (PE) reflector
Atomic density

Isotope(×1024/cm3)
19” Polyethylene

1/2” thick plate1/4” thick plate1/8” thick plateH

8.06560×10-2

8.08711×10-2

8.02167×10-2

8.00083×10-2

C

4.03280×10-2

4.04356×10-2

4.01084×10-2

4.00042×10-2

16square rod

Table 1-5 Atomic densities of graphite (Gr) plate
Atomic density

Isotope(×1024/cm3)
8.60664×10-2

C

Table 1-6 Atomic densities of beryllium (Be) plate
Atomic density

Isotope(×1024/cm3)
1.22932×10-1

Be

Table 1-7 Atomic densities of control and safety rods
Atomic density

Isotope(×1024/cm3)

10

B

3.87448×10-3

11B

1.68447×10-2

16

O

3.10787×10-2

Table 1-8 Atomic density of aluminum sheath for the core element
Atomic density

Isotope(×1024/cm3)
6.00385×10-2

Al

17

Table 1-9 Atomic densities of 93Nb, 112Cd, 115In and 197Au

Foil(wire)
92

Nb

Abundance

PurityAtomic density

(%)

(%)

(×1024/cm3)

100

99.9

5.54947×10-2

106

1.25

99.99

5.39648×10-4

108

Cd

0.89

99.99

3.91477×10-4

110

Cd

12.51

99.99

5.59564×10-3

111

Cd

12.81

99.99

5.78677×10-2

112

24.13

99.99

1.10072×10-2

113

12.22

99.99

5.62419×10-3

114

28.72

99.99

1.33398×10-2

116

7.47

99.99

3.53884×10-3

113

4.29

99.99

1.64406×10-3

115

In

95.71

99.99

3.66790×10-2

197

Au

100

99.95

5.90403×10-2

Isotope
92

Nb
Cd

Cd
Cd
Cd
Cd
Cd
In

In
197

Au

18

2. Core Configuration

10

11

12

13

14

15

16

17

18

19

20

O

TP

Thorium fuel and polyethylene (Th-PE)

In wire position

P
Q(Th-Gr; Th-Be; Th-HEU-PE; NU-PE)

3He #2R

Polyethylene

3He #3

T

TP

TP

TP

TP

TP

U

TP

TP

TP

TP

TP

V

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

W

3He #1X

3

He detector
1” diameter void

Tritium target

Deuteron beams

Y
Z

Fig. 2-1 Thorium-loaded ADS core configuration with 14 MeV neutrons(Th-PE, Th-Gr, Th-Be, Th-HEU-PE and NU-PE)

20

19

18

17

16

15

14

13

12

11

10

K

TP
In wire position

J
I

Polyethylene

3He #3

G

TP

TP

TP

TP

TP

E

TP

TP

TP

TP

TP

D

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

TP

A

(Th-Gr; Th-Be; Th-HEU-PE; NU-PE)

3He #2

H

B

Thorium fuel and polyethylene (Th-PE)

3He #1

3

He detector

Tungsten target

A'

Proton beams

Fig. 2-2 Thorium-loaded ADS core configuration with 100 MeV protons(Th-PE, Th-Gr, Th-Be, Th-HEU-PE and NU-PE)

19

Polyethylene

10

11

12

13

14

15

16

17

18

19

20

O

T5P
In wire position

P
Q

3He #1

Thorium, HEU fuel and polyethylene (Th-HEU-5PE)(Th-HEU-Gr-PE)

3He #2R

Polyethylene

T

T5P T5P T5P T5P T5PU

T5P T5P T5P T5P T5PV

T5P T5P T5P T5P T5PW

T5P T5P T5P T5P T5PX

T5P T5P T5P T5P T5P

3

He detector

Tritium target

Deuteron beams

YZ

Aluminum sheathFig. 2-3 Thorium-loaded ADS core configuration with 14 MeV neutrons(Th-HEU-5PE and Th-HEU-Gr-PE)

20

19

18

17

16

15

14

13

12

11

10

K

T5P
In wire position

JI

3He #1

Thorium, HEU fuel and polyethylene (Th-HEU-5PE)(Th-HEU-Gr-PE)

3He #2H

Polyethylene

G

T5P T5P T5P T5P T5P

E

T5P T5P T5P T5P T5P

D

T5P T5P T5P T5P T5P

B

T5P T5P T5P T5P T5P

A

T5P T5P T5P T5P T5P

3

He detector

Tungsten target

A'

Proton beams

Fig. 2-4 Thorium-loaded ADS core configuration with 100 MeV protons(Th-HEU-5PE and Th-HEU-Gr-PE)

20

Table 2-1 List of thorium-loaded ADS cores

Core

Cell patter

keff

Th-PE

1/8”Th+1/2”PE

0.00613

Th-Gr

1/8”Th+1/2”Gr

0.00952

Th-Be

1/8”Th+1/2”Be

0.00765

Th-HEU-PE

1/8”Th+1/16”HEU+3/8”PE

0.58754

NU-PE

1/8”NU+1/2”PE

0.50867

Th-HEU-5PE

1/8”Th+5*(1/16”HEU+3/8”PE)

0.85121

Th-HEU-Gr-PE

1/8”Th+4*(1/16”HEU+1/2”Gr)+1/8”PE

0.35473

Th: Thorium; PE: Polyethylene; Gr: Graphite; Be: Beryllium;
HEU: Highly-enriched uranium; NU: Natural uranium

21

3. Results of Experiments
3-1. Thorium plate irradiation experiment

Table 3-1 Criticality position at the critical state (Th plate irradiation experiment)Rod

Rod position [mm]C11201.21C2

1201.18C3

567.01S4

1200.00

S5

1200.00

S6

1200.00

Excess reactivity[%Δk/k]0.225

Table 3-2 Measured results of Au foils, Cd ratio and thermal neutron flux
Parameters

Results in Experiments

Au foil (Bare)

Reaction rate [1/s/cm3](4.76 ± 0.02)×108

Au foil (Cd covered)

Reaction rate [1/s/cm3](1.62 ± 0.01)×108

Cd ratio-

2.93 ± 0.02

Thermal neutron flux

Neutron flux [1/s/cm2](5.87 ± 0.05)×107

22

Table 3-3 Nuclides and characteristics of γ-ray measurements of thorium reactions

Reaction

CaptureFissionEmissionYield of fission(T1/2)

Emission γ-ray
energy [keV]

rate [%]

product [%]

233

Pa

26.95 d

311.9

38.60

-

91

Sr

9.48 h1024.3

34.01

7.36

92

Sr

2.71 h1383.9

90.00

6.92

97

Zr

17 h

743.4

94.60

4.43

135

I

6.7 h

1260.5

30.28

5.52

142

La

1.55 h

641.2

48.90

6.54

NuclideHalf-life

Table 3-4 Measured results in reaction rates of thorium capture and fission reactions

Reaction

CaptureFission

NuclideReaction rate
3

Fission rate

[1/s/cm ][1/s/cm3]233

Pa(5.82 ± 0.01)×106

-

91

Sr

(1.05 ± 0.01)×104(1.42 ± 0.04)×105

92

Sr(1.01 ± 0.01)×104(1.46 ± 0.05)×105

97

Zr(6.52 ± 0.04)×103(1.47 ± 0.02)×105

135I(8.28 ± 0.07)×103(1.50 ± 0.04)×105

142

La

(1.14 ± 0.01)×104(1.56 ± 0.05)×105

23

311.9 keV (233Pa)

106

743.4 keV (97Zr)
1383.9 keV (92Sr)

Counts [1/s]

105
104
103
102
101

0

500

1000

1500

2000

2500

3000

Energy [keV]

Fig. 3-1 Measured γ-ray spectrum of irradiated thorium plate in the critical state

3-2. Reaction rate distribution

40.0
Reaction rates [1/s/cm3/source]Core region

Polyethylene
region
Th-PE

30.0

Th-Gr
Th-Be

20.0

Th-HEU-PE
NU-PE

10.0

0

0

10

20

30

40

Distance from 3H target [cm]Fig. 3-2 Comparison between the measured reaction rates of indium wire obtained from theTh-loaded ADS experiment with 14 MeV neutrons for Th-PE, Th-Gr, Th-Be, Th-HEU-PE
and NU-PE cores

24

Reaction rates [1/cm3/s/source]

20.0

Polyethylene
regionCore region

Th-PE core

15.0

Th-Gr core
Th-Be core

10.0

Th-HEU-PE core
NU-PE core

5.0

0

0

10

20

30

40

Distance from boundary between (14, 13 - A, A') [cm]Fig. 3-3 Comparison between the measured reaction rates of indium wire obtained from theTh-loaded ADS experiment with 100 MeV protons for Th-PE, Th-Gr, Th-Be, Th-HEU-PE
and NU-PE cores

10.0
Polyethylene
region8.0

3

Reaction rate [1/s/cm /source]Core region

6.0

4.0
Th-HEU-5PE core
Th-HEU-Gr-PE core

2.0

0

0

10

20

30

40

3

Distance from H target [cm]Fig. 3-4 Comparison between the measured reaction rates of indium wire obtained from theTh-loaded ADS experiment with 14 MeV neutrons for Th-HEU-5PE and Th-PE-Gr-PE
cores

25

Reaction rate [1/s/cm3/source]

20.0Core region

Polyethylene
region15.0

10.0
Th-HEU-5PE core

5.0

0Th-HEU-Gr-PE core

0

10

20

30

40

Distance from boundary between (14, 13 - A, A') [cm]Fig. 3-5 Comparison between the measured reaction rates of indium wire obtained from theTh-loaded ADS experiment with 100 MeV protons for Th-HEU-5PE and Th-PE-Gr-PE
cores

3-3. Time evolution data of PNS and Noise methods
Table 3-5 List of subcriticality data in all the cores shown in Table 2-1

Core

14 MeV neutrons

100 MeV protons

PNS method

Noise method

PNS method

Noise method

Th-PE

Available

Available

-

-

Th-Gr

Available

Available

-

-

Th-Be

Available---

Th-HEU-PE

Available

Available

Available

Available

NU-PE

Available---

Th-HEU-5PE

Available

Available

Available

Available

Th-HEU-Gr-PE

Available

Available

Available

Available

PNS method: Pulsed neutron source method; Noise method: Feynman-α method

26

Table 3-6 Time evolution data of thorium-loaded cores on the PNS and Noise methods

Core

14 MeV neutrons

100 MeV protons

Repetition [Hz]Width [μs]Repetition [Hz]Width [ns]

Th-PE

100

10

-

-

Th-Gr

100

10

-

-

Th-Be

100

10

-

-

Th-HEU-PE

100

10

20

60

NU-PE

100

10

-

-

Th-HEU-5PE

10

10

20

100

Th-HEU-Gr-PE

10

10

20

100

Table 3-7 Measured results in neutron decay constants deduced by least-squared fitting in PNS method
Neutron decay constant α [1/s]
14 MeV neutrons
Core

3

He #1

3

He #2

100 MeV protons
3

He #3

3

He #1

3

He #2

3

He #3

Th-PE

6642±116224±275751±25

-

-

-

Th-Gr

6451±125945±155701±17

-

-

-

Th-Be

6515± 86111±175746±20---

Th-HEU-PE

5692±115275± 75231± 95777±115527±355236±37

NU-PE

5748±116592±155010±11---

Th-HEU-5PE

3110±113104±10-2776±172917± 8-

Th-HEU-Gr-PE

4980±404939±50-

3186±724656±12-27

Table 3-8 Measured results in subcriticality in dollar unit deduced by extrapolated area ratio method
Subcriticality ρ [$] (by Area ratio method)
14 MeV neutrons
Core

3

He #1

3

He #2

100 MeV protons
3

He #3

3

He #1

3

He #2

3

He #3

Th-PE

144.77±1.56

1051.97±28.70

2778.37±135.26

-

-

-

Th-Gr

108.47±18.06

400.34±5.92880.49±20.41

-

-

-

Th-Be

33.42±0.17

37.04±0.16

105.35±0.85

-

-

-

Th-HEU-PE

12.05±0.03

29.75±0.09

63.53±0.3532.30±0.45

26.52±0.29

44.27±0.74

NU-PE13.40±0.04

26.64±0.1282.76±0.57

-

-

-

Th-HEU-5PE

16.61±.0.21

11.35±0.09-

3.77±0.01

10.35±0.05-

Th-HEU-Gr-PE

63.76±1.4242.92±0.66-

3.83±0.30

64.54±11.13-

28