PR11 Studies on Actinides and Fission Products Performed at the KURRI Hot Laboratory
T. Fujii

ARS-17 40Ar/39Ar dating of neutron irradiated minerals
and glasses (O. Ishizuka et al).
ARS-18 Radiometric Ar-Ar dating of neutron irradiatedlavas (N. Hirano et al.).

Research Reactor Institute, Kyoto University
1. Objectives and Allotted Research Subjects
Studies on actinide and fission product nuclides withcareful management are being more important for reprocessing, disposal, partitioning, and transmutation processes in the nuclear fuel cycle. Hot laboratory of KURRI is one of core facilities in Japan, in which various
nuclides can be handled. This project enhances utilizationof the KURRI hot laboratory by opening for fundamental
and application studies related to radiochemistry, nuclear
chemistry, environmental chemistry, geochemistry, andso on. Allotted research subjects are;
ARS-1 Complexation of actinides with organic substances (T. Sasaki et al.).
ARS-2 Solubility of actinide compounds in aqueous
media (T. Kobayashi et al.).
ARS-3 Leaching of actinides and FPs from fuel debris(N. Sato et al.).
ARS-4 Neutron irradiation damage of vitrified waste
matrices (T. Nagai et al.).
ARS-5 Ligand exchange reaction of actinides in molten
salts (A. Uehara et al.).
ARS-6 Electrochemical behavior of uranium in pyroreprocessing system (Y. Sakamura et al.).
ARS-7 Structural study of f-elements in molten halides(H. Matsuura et al.).
ARS-8 Molecular dynamics simulation of uranyl ion in
molten salts (N. Ohtori et al.)．
ARS-9 Fundamental study of fission products fortrans-actinide chemistry (Y. Kasamatsu et al.).
ARS-10 Isotope separation by using microreactor (R.
Hazama et al.).
ARS-11 Optical properties of molten aluminum halides(T. Goto et al.).
ARS-12 Precipitation of f-element oxides in molten halides (H. Sekimoto et al.).
ARS-13 Uptake of radiocesium and radiopotassium inplants (T. Ohta et al.).
ARS-14 Quantitative analysis of radionuclides in seawater (T. Kubota et al.).
ARS-15 Isotopic composition of radionuclides in environmental samples (Y. Shibahara et al.).
ARS-16 Noble gas mass spectrometry of neutron irradiated geological samples (H. Sumino et al.).

採択課題番号

2. Main Results and Contents
ARS-1, 2, 3, and 4 were performed in order to deepen theknowledge of nuclear waste management issues. In
ARS-1 and 2, stability constants and solubility productsof actinides were obtained. In ARS-3, leaching kinetics
of actinides and FPs from irradiated Zr alloy was clarified. In ARS-4, a structural change of borosilicate byneutron irradiation was found. ARS-5, 6, 7, and 8 were
performed with the viewpoint of pyroreprocessing. In
ARS-5 and 7, ligand exchange of F- and Cl- for U4+ andNd3+ in molten halides was clarified. In ARS-6, effective
diffusion coefficient of U3+ in porous Zr was determined.
In ARS-8, atomic distances of UO2+ in LiCl melt werecomputed. Polarization of Cl- around UO22+ was found.
ARS-11 and 12 seek applications of molten salt systems
for industrial use, for example, refining. ARS-11 studied
optical properties of molten alkaline chlorides containing
Al. Raman spectra obtained were interpreted by using ab
initio method. ARS-12 focuses on recycling of rare earths.
Solubility of Dy(III) under the coexistence of Dy oxide
and oxychloride in chloride melts was discussed. ARS-10
studied isotope fractionation of Ca. A possible fractionation of 48Ca/40Ca was found. ARS-13, 14, and 15 studied
on redionuclides in soils, plants, seawater, and so on. In
ARS-13, distribution of radiocesium in plants was clarified. ARS-14 presented an effective preparation methodof radiotracers which are useful for environmental science. ARS-15 suggested that precise isotopic analysis of
Cs and Sr is helpful for a rapid source analysis of nuclear
accident. ARS-16, 17, and 18 demonstrated that neutron
irradiation at KUR is usable for the Ar-Ar and I-Xe dating of geological samples.
3. Summaries of the achievements
In this research, by using various unique facilities of
KURRI for actinides and fission products, new and characteristic chemical, kinetic, structural, and thermodynamic data were obtained. These new information encompass solid chemistry, molten salt and solution chemistry, as well as nuclear reactions of f-elements and FPs.
The results are useful either for scientific purpose or fortechnological purpose for nuclear science, environmental
science, geoscience, and general industry.

26P11

ホットラボラトリを活用したアクチニドおよび核分裂生成物元素の化学研究（京大・原子炉）藤井俊行
52

プロジェクトPR11-1

Apparent Formation Constant of Metal Ions with Humic Substances; Modelling

T. Sasaki, T. Kobayashi, T. Koukami, A. Uehara1, T. Fujii1, H. Yamana1, H. Moriyama1

representative values for the intramolecular chelating
effect of the bidentate site fraction. In the case of tetravalent metal ions, the hydrolysis reactions are taken into
account for the analysis of the experimental datasets [3].

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

RESULTS:
The present model fairly well reproduced the literatureapparent formation constants of tetravalent Pu/Th (Fig.1),
pentavalent Np, divalent Ca/Co, and trivalent Al/Eu withthe hypothetical humic acid and of tetravalent Th, pentavalent Np, divalent Mg/Ca/Co/Mn/Ni/Cu/Zn/Pb, andtrivalent Eu with the hypothetical fulvic acid under awide range of pH, I, and initial HSs and metal concentration [3]. Some discrepancies between the calculated andexperimental values were recognized and discussed; oneis the I dependence of the values of some metal ions suchas neptunium, and the other is the discrepancy observed
for the system of ultra-trace amount of neptunium, suggesting further effects of not yet identified but muchstronger binding sites in HS. Although the present hypothetical structure is only one example of HS, it provides abasis for further studies of the thermodynamic and kinetic
parameters for complexation reactions.

INTRODUCTION:
A semi-empirical thermodynamic model was developed
to estimate the apparent formation constants of metal ionswith humic substances (HSs), humic and fulvic acids,
over a wide range of solution conditions, i.e., pH, ionicstrength, and HS and metal concentrations.
To understand the fundamental rules of metal complexation with HSs, many researchers have attempted tocharacterize the physical and chemical properties of HSs
in soils, sediments, and natural waters. It has been determined that randomly cross-linked heterogeneous organic
substances generally have similar distributions of a number of specific functional groups, including carboxyl,
phenolic, and alcoholic groups. Towards the ultimate goalof characterizing natural HSs, researchers have proposed
hypothetical HS chemical structures based on results obtained using several analytical methods.
The discrete fragment model has been proposed byour group; it decomposes the organic ligands into discrete
fragments of functional groups and chelating bridges thatconnect the functional groups. The ligand fragments
called as basic ligands were clipped from a “pragmatic”
chemical structure of a humic acid (HA) proposed [1],which were distributed statistically in the HA framework.
The fixed formation constant values of the metal ion witheach ligand was taken from the literature; benzoic acid,
phthalic acid, isophthalic acid, 1,2,3-benzenetricarboxylicacid, 1,2,4-benzenetricarboxylic acid, 2-hydroxybenzoic
acid, phenol, butanedioic acid, and acetic acid. The stericeffect of bidentate binding sites due to the additional stabilization by chelate formation was considered, while theelectrostatic surface potential of the HA molecule in solution was not considered for simplification. The model has
yielded satisfactory results for the apparent complex formation constant of trivalent europium with Aldrich HA
under varied solution conditions, including pH, ionicstrength, and the concentrations of metal ions and HA [2].

Th(OH) - IHSS 1S102H [3]14log βapp

1210
8
6
pH4.7, I=0.1, CM=4E‐9〜6E‐8M
pH4.7, I=0.1, CM=1〜6E‐7M
pH4.9, I=0.01, CM=1〜6E‐8M
pH4.8, I=0.1, CM=1〜6E‐9M

4
2

-8

-6

logCR

-4

-2

Fig.1. Example of comparison between the experimental
apparent formation constants app of Th(IV) with humic
acid (purchased from IHSS) and the simulated curves; CR,molar concentration of HS, CM, initial concentration of
metal ion.
REFERENCES:[1] Schulten, H. R., Schnitzer, M. Naturwissenschaften,
80 (1993) 29–30.
[2] Sasaki, T., Kobayashi, T., Takagi I., Moriyama, H. J.
Nucl. Sci. Technol., 45 (2008) 718–724.
[3] Sasaki, T., Yoshida, H., Aoyama, S., Kobayashi, T.,
Takagi I., Moriyama, H. Radiochimica Acta. (2015) inpress.

THEORETICAL:
The model was modified and applied to several kinds ofmetal ions including actinides, i.e., Th(IV), Pu(IV), and
Np(V), according to following steps; 1) a number of datasets for acid dissociation of various HSs were analyzed
to obtain the representative values for the abundance ratios of the basic ligands and the heterogeneity parameterof HSs, 2) the datasets for complexation of various multivalent metal ions with HSs were analyzed to obtain the

採択課題番号26P11-1
アクチニド元素の水溶液内錯生成反応に関する研究
プロジェクト（京大院・工）佐々木隆之、小林大志、鴻上貴之（京大・原子炉）上原章寛、藤井俊行、山名 元、
森山裕丈
53PR11-2 Temperature Effect on the Solubility and Solid Phase of Tetravalent Metal Hydroxide
T. Kobayashi, T. Sasaki, A. Uehara1, T. Fujii1,
H. Yamana1, H. Moriyama1

indicating the progress of crystallization of initial amorphous hydroxide. The Ksp values after aging at different
temperatures were determined from the analysis of thesolubility dataset in Fig.1. After aging at 60ºC, the solubility was measured at 5, 25, 40 and 60ºC (Fig. 2 ) andthe Ksp at different temperatures. Assuming no temperature dependence of enthalpy change (ΔrHº), the ΔrHº was
calculated for Zr4+ + 4OH– <=> Zr(OH)4 (s,60ºC), whereZr(OH)4 (s,60ºC) represents the solid phase formed at
60ºC. The obtained ΔrHº was slightly higher than theΔrHº (–133.6 kJ/mol) for Zr(OH)4(am) calculated fromthe standard enthalpy of formation [3]. Similar analysis
was performed for the solubility after aging at 5 and 40ºC,
and a trend of ΔrHº for the solid phases formed at different temperatures suggested that the solid phase transformation is endothermic reaction within the investigatedtemperature range.

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

1

INTRODUCTION:
The decay heat emission from vitrified high level radioactive waste in the repository will be transferred to
groundwater aquifers through surrounding engineered
and geological barrier systems. In the early failure scenario of the waste package, long-lived radionuclides including tetravalent actinides (An(IV)) leached in the
groundwater are considered to be exposed to an elevatedtemperature environment up to 100°C [1]. For the safetyassessment of geological disposal, it is required to evaluate a possible impact of elevated temperature on the solubility of An(IV). At 25ºC, the steady-state solubility is
generally controlled by amorphous hydroxide as solubility-limiting solid phase, and described using relevant
thermodynamic constants [1]. However, the amorphoushydroxide was dehydrated and crystalized at elevatedtemperature [2]. Therefore, the thermodynamic estimation of An(IV) solubility needs to clarify the both of hydrolysis constants and solubility product (Ksp) at a given
elevated temperature [3].
In the present study, the apparent solubility of zirconium hydroxide as chemical analogue for An(IV) and the
crystallinity of the solid phase were investigated under
several conditions of temperature (5 to 60ºC). The temperature dependence of solubility product and the enthalpy change were discussed.

-2-2
Zr(OH)4(s)Tmeas = 25°C
Taging[2]
90°C [1]
60°C
40°C
[4]
25°C [2]
5°C

-3

-3
-4

-5

log [Zr]log [Zr]-4

Measurement
Temp. 25ºC

-6

-5
-6

-7

-7

-8

-8

Aging
Temp.60ºC

-9

-9
0

1

2

3

+

4

5

6

-log [H ]EXPERIMENTS:
Sample solutions by oversaturation method were prepared by adding NaOH or HClO4 to the acidic Zr perchlorate solutions ([Zr] = 0.01 mol/dm3 (M)). The ionicstrength (I) was adjusted to be I = 0.5 by adding appropriate amount of NaClO4. After aging the sample solutions in temperature chambers controlled at 5ºC, 40ºC
and 60ºC, the samples were transferred to the thermostat
dry-bath followed by the ultrafiltration and pH measurement at different temperature conditions. After filtrationof supernatants through the ultrafiltration membranes (3kDa – 100 kDa NMWL, Millipore), the apparent solubility of zirconium was determined by ICP-MS. XRD wasused to characterize the crystallinity and the particle sizeof the solid phase.

Taging Tmeas
60°C 60°C
60°C 40°C
60°C 25°C
60°C
5°C

Fig. 1. Solubility ofZr(OH)4(s) after aging atdifferent temperatures.

0

1

2

+

3

4

-log [H ]Fig. 2. Solubility ofZr(OH)4(s) measured at
different temperatures
after aging at 60ºC.

REFERENCES:[1] 2nd progress report on research and development for
the geological disposal of HLW in Japan, JNC Report
TN1410 2000-001, JNC, Tokai, Japan.
[2] Kobayashi T. et al., Radiochim. Acta, 101, (2013)645.
[3] Brown P. et al., Chemical Thermodynamics of Zirconium, Elsevier, North-Holland, Amsterdam (2005).
[4] Sasaki, T. et al., Radiochim. Acta 94, 489 (2006).

RESULTS:
The apparent solubility after aging at 40 and 60ºC andmeasured at 25ºC were lower than those kept at 25ºC,

採択課題番号26P11-2 アクチニド元素および放射性核種の溶解沈殿反応に関する研究 プロジェクト（京大院・工）小林大志、佐々木隆之（京大・原子炉）上原章寛、藤井俊行、山名 元、森山裕丈
54

PR11-3

Research on the Behavior of Actinides and FPs in Fuel Debris
spectrometry were performed using a Ge detector and
Si detector to determine the nuclides leached.
RESULTS:
Figure 1 shows the leaching ratios (R(%)) of
actinides to seawater. There, the clear timedependence cannot be seen in the leaching of
Np, Am and Pu during 31 days leaching test.
Also, their leaching ratios were supressed in
the very low extent (0.02 % or less). The leaching of these actinides are expected to be supressed to very low extent regardless of the oxidation state in the solid phase since the solubilities of both M(III) and M(IV) for Am and Pu,
and Np(IV) are very low at the pH of seawater.
On the other hand, the RU value was about
0.1 % during the leaching test. From this result,
it is considered that the uranium dissolution
from the simulated fuel debris was governed by

N. Sato1, A. Kirishima1, M. Hirano, T. Sasaki2, T.
Kobayashi2, Y. Takeno2, A. Uehira3, T. Fujii3, K.
Takamiya3 and H. Yamana3
1

Institute of Multidisciplinary Research for Advanced
Materials, Tohoku University
2
Graduate School of Engineering, Kyoto University
3
Research Reactor Institute, Kyoto University
INTRODUCTION:

After the LOCA of Fukushima Daiichi NPS, the melted core reacted with coolant at high temperatureforming fuel debris containing fuel and structural materials such as zirconium. Under high temperature
condition in the pressure vessel, several kinds of FPs
and TRU were possibly released into the cooling water
mixed with seawater and the air from the melted coreand its fine debris. Information on the radionuclide
behavior in fuel debris and surface seawater will be
helpful to analyze the forthcoming analysis data about
the contents of minor FPs and TRU in contaminatedwater, and to manage associated secondary wastes.
First, the simulated fuel debris composed of uranium
and zirconium oxides as main constituents was prepared by heat treatment in reductive or oxidative conditions. Then the dissolution behavior of typical gamma-ray fission products and neutron activated nuclides
as well as uranium in solid solutions was investigatedby neutron irradiation and following leaching in the
non-filtrated seawater. Dissolution behavior of MA
was also studied by the used of MA doped simulated
fuel debris.
EXPERIMENTAL:
Three types of UO2-ZrO2 solid solution samples with
Zr concentration of 10, 50 and 90 mol% were preparedby mechanochemical and heat treatments under reductive and oxidative atmosphere. The sample was vacuum-sealed in quartz tube and irradiated for 20 min
using the pneumatic transferring system (Pn-2) at
KUR. For reducing the high radioactivity ofshort-lived nuclides, the sample was left in glove box,
and then suspended in 30 ml of fresh seawater from
Minamisoma city, Fukushima. After the aging time in
the atmospheric condition at R.T., a 10 mL of supernatant was transferred to new sample tube after filtration with 0.45 m (Advantec) or 3 kDa (Microcon,
Millipore) membranes, followed by evaporation of theseawater at 363 K in order to repare a solidified
point-like source. For MA doped sample, similar preparation techniques were applied by using U3O8 powder
with 237Np, 243Am and 236Pu. Gamma- and alpha- ray

the solubility limitation of UO3 2H2O(cr), UO3･
2H2O (am) or maybe their intermediate phaseas discussed in our previous study [1]. These
results suggest that both dissolution andstructure data are essential for fuel debris behaviour. In further study, behavior of actinides
and FP’s from different types of fuel debris will
be discussed.

Figure 1 Time dependence of actinides leaching from thesimulated fuel debris to the Fukushima seawater [2].
REFERENCES:[1] T. Sasaki, Y. Takeno, A. Kirishima, N. Sato, J. Nucl.
Sci. Technol., 52 (2015) 146-150.
[2] A. Kirishima, M. Hirano, T. Sasaki, N. Sato, J. Nucl.
Sci. Technol., in press, doi: 10.1080/00223131.2015.
1017545.

採択課題番号 26P11-3
燃料デブリ中のアクチノイドおよび FP 元素の挙動に関する研究
プロジェクト （東北大多元研）佐藤修彰、桐島 陽、平野正彦（京大院工）佐々木隆之、小林大志、竹野 佑（京大・原子炉）上原章寛、藤井俊行、高宮幸一、山名 元

55PR11-4

Effect on Borosilicate Glass Structure by Neutron Irradiation

T. Nagai, A. Miyauchi, Y. Morikawa, A. Uehara1, and T.
Fujii1

ation, it could be observed that the peak heights of Q4 andQ3 decreased and those of Q2 and Q1 increased after theirradiation, as shown in Fig. 1. These height changes ofQn, n=1-4, suggested the feasibility that a generated Li by
the neutron irradiation disconnects the Si-O bridging
structure in a borosilicate glass. However, this Si-O
bridging structure is direct disconnected by γ ray included in the neutron irradiation and the additional experiments needs for understanding of the irradiation effect.

Japan Atomic Energy Agency (JAEA)
1
Research Reactor Institute, Kyoto University
INTRODUCTION: A high-level radioactive liquid
waste including fission products, FPs, from a reprocessing process for spent nuclear fuels is processed into asolidified waste glass made by using a borosilicate glass
as media. Many studies of the effect on borosilicate glass
structure by irradiation have been carried out by irradiation of α ray, β ray, and γ ray which would be generated
from FPs of the waste glass. However, that effect by aneutron irradiation has not been much evaluated. In thisstudy, the borosilicate glass samples were irradiated byneutrons, and the glass structure change after the irradiation was measured by Raman spectrometry.

1.2

non-irradiation
irradiation for 10 min

normalized intensity

1

EXPERIMENTS: The borosilicate glass samples wereprepared 2 compositions. The raw material reagents of
SiO2, H3BO3, Na2CO3, Li2CO3, and rare earth oxides assimulated FPs were placed in an alumina crucible andwere melted at 1150°C in an electric furnace. After themolten samples were solidified by cooling to room temperature, they were cut into thin plates. In the irradiation,
the glass samples of thin plate were set in a polyethylene
tube and were irradiated under the condition of 1000 kW
for 10 min in the Pn-2 of KUR. After the radioactivity ofthe samples was sufficiently attenuated, the Raman spectra of the glass sample were measured by using a laser
Raman spectrometer, NRS-3100 of JASCO. For the effect on borosilicate glass by the nuclear reaction of
10
B(n,α)7Li, Peuget, et al have evaluated the B-O structure by using NMR measurement and Raman spectrometry[1], our study was examined the Si-O structure.

0.8

Q3
0.6

Q2
0.4

Q4

0.2

Q1
0
1250

1200

1150

1100

1050

1000

Raman shift (cm-1)

950

900

850

(1) 63SiO2-16.6B2O3-19Na2O-1.4RE2O3.
1.2

non-irradiation
irradiation for 10 min

normalized intensity

1

RESULTS: As a structural change of the sample by theirradiation, an amount of Li would be increased by the10
B(n,α)7Li reaction, and Li was expected to disconnect
to the Si-O bridging structure. By evaluating the Raman
shift of the Si-O structure, it was confirmed to be the effect on the borosilicate glass structure by the irradiation.
The Raman shifts of Si-O structure of a silicate glass
were in the wavenumber of 850-1200 cm-1, and the peak
positions of Raman shifts were different from the numberof non-bridging oxygen, NBO, of the Si-O structure.[2] In
this measurement of borosilicate glass, those Raman
shifts were observed in 850-1250 cm-1 and the measured
spectra could be separated into Gaussian waves as shownin Fig. 1. The Raman peak of Q4 structure without NBO
appeared in 1140-1150 cm-1, and those of Q3, Q2, and Q1
structures with the NBO number = 1, 2, and 3 were in
1070-1090, 1000-1020, and 920-930 cm-1 respectively.
Comparing with the Raman shifts before and after irradi-

0.8

Q2
0.6

Q3
0.4

Q4

0.2

0
1250

Q1

1200

1150

1100

1050

1000

Raman shift (cm-1)

950

900

850

(2) 63SiO2-16.6B2O3-8.1Li2O-10.9Na2O-1.4RE2O3.
Fig. 1. Raman spectra of glass samples and their separated Gaussian waves. Open circles and fine lines
are a non-irradiation sample, and closed circles anddotted lines are after irradiation.
REFERENCES:[1] S. Peuget, et al, Nucl. Inst. Methods in Phys. Res. B,
327 (2014) 22-28.
[2] P. McMillan, Am. Mineralogist, 69 (1984) 622-644.

採択課題番号 26P11-4 中性子照射によるホウケイ酸ガラス構造への影響評価
プロジェクト（原子力機構）永井崇之、守川 洋、宮内厚志（京大・原子炉）藤井俊行、上原章寛
56PR11-5

Ligand Exchange of Uranium (IV) Chloro- and Fluoro- Complexes in High
Temperature Molten NaCl-CsCl Eutectic
analysis data of U4+ in CsCdBr 3 [2] and LiYF 4 [3],absorption bands of the 5f 2-5f 2 transition of U4+ wereassigned as follows; the 1I 6 ← 3H 4 transition at
22500-19000 cm-1, the 3P 1 ← 3H 4 transition at 17800
cm-1, the 1G 4 , 1D 2 , 3P 0 ← 3H 4 transition at
17000-14000 cm-1, the 3H 6 ← 3H 4 transition at
13100-12000 cm-1, the 3F 3 , 3F 4 ← 3H 4 transition at
11100-7500 cm-1, and the 3H 5 ← 3H 4 transition at
6500-5000 cm-1.

A. Uehara1, T. Nagai2, T. Fujii1, H. Moriyama1, and H.
Yamana1
Research Reactor Institute, Kyoto University
Nuclear Fuel Cycle Engineering Lab., Japan Atomic
Energy Agency

1
2

INTRODUCTION:

In the non-aqueous reprocessing process of spent nuclear fuels by the pyrometallurgical and the electrowinning methods, a spent fuel is dissolved into
molten LiCl-KCl or NaCl-CsCl eutectic melt and dissolved uranium and plutonium ions are recovered as
metal or oxide. In the present study, the chemical
property and coordination circumstance of the complexes of U4+ under the coexistence of fluoride ions inmolten NaCl-CsCl eutectic were investigated by absorption spectrum measurements.

molar absorptivity/ M-1cm-1

10

U4+-Cl complex
5

EXPERIMENTAL:

All experiments were carried out under an argon atmosphere, in which humidity and oxygen impurity
were continuously kept less than 1 ppm. The electronic absorption spectra of uranium ions in the melts were
measured by using an UV/Vis/NIR spectrometer(V-570, JASCO Co.). The analytical light from a lightsource (a tungsten halogen lamp and D 2 O lamp) was
guided to the electric furnace with quartz windows byusing optical fibers, and the light passed through thesample in a quartz tube with a 10 mm light path inside
the furnace. The light which traveled through the furnace was again guided to the spectrophotometer, and a
monochromator was set in front of the detectors todecrease the background noise. The light intensity forthe molten alkali chloride (I 0 ) and that including uranium (I) was measured in the wavelength range of 300– 2000 nm at 1 nm intervals. Wavelength was converted to wavenumber in this work. The molar absorptivity was calculated by using –log (I/I 0 ) and total
volume of the solution. All the experiments were performed at 923K ± 3K.

U4+-F complex
0
23000

20000

17000

[F]/[U]
0
0.09
0.17
0.31
0.47
0.89
1.3
1.7
2.6
9.5
17

14000

wavenumber / cm-1

Fig. 1. Molar absorptivity of U4+ depended on the concentration of NaF in molten NaCl-CsCl eutectic at 923K.
Concentration ratios of F- by U4+ (r F ) are 0, 0.09, 0.17,
0.31, 0.47, 0.89, 1.3, 1.7, 2.6, 9.5, and 17.

When 9.36 × 10-3 M NaF was added in the melt, absorption peaks decreased. Molar ratio of fluorine byuranium (r F ) added in the melt was changed from 0.09
to 17 by adding NaF pellet as shown in Fig. 1. Absorption peaks corresponding to 14903, 16501, and 22123
cm-1 decreased with the increase of r F from 0.09 to 1.7
and isosbestic points at 13774, 15772, 16181, 17793,
and 19305 cm-1 were observed. This result means that
two species of complexes composed of U4+, Cl- and Fare equilibrated. However, when r F was over 9.5, another peaks at 15847, 17331, and 19646 cm-1 wereobserved. This indicates that another complex composed of U4+, Cl-, and F- is formed. After 10 hours aging, red color precipitates were found on the bottom of
the cell.
REFERENCES:[1] Nagai, et al., J. Nucl. Sci. Technol., 42,1025-1031 (2005).
[2] Karbowiak, et al., Chem. Phys., 308, 135-145

RESULTS:

Molar absorptivity of absorption spectra of U4+ in thepresence of F- was plotted as a function of wavenumber in Fig. 1. When an absorption spectrum of
0.106 M U4+ in the absence of F- was measured, molar
absorptivities of each peak wavenumber at 14903,
16501 and 22123 cm-1 agreed with the reported values[1]. By comparing these values with the crystal field(2005)[3] Hubert, et al, J. Luminescence, 60&61, 245-249(1994)

採択課題番号 26P11-5
イオン液体中におけるアクチニドイオンの溶存状態研究（京大・原子炉）上原章寛、藤井俊行、森山裕丈、山名 元（原子力機構）永井崇之

57

プロジェクトPR11-6

Evaluation of Parameters Governing Anodic Dissolution of
U-Zr Alloy in Molten LiCl-KCl

M. Iizuka1, Y. Sakamura1,
T. Fujii2, A. Uehara2 and H. Yamana2

or simple multi-diffusion layer model [1]. Then, the series of the electrochemical operations, including the CP
measurement at constant current density and the rest period in open circuit situation between the measurements,
were digitally simulated by discretization of the diffusion
layers around the U-Zr alloy into elements of 10 to 20µm thickness using finite element method. The calculation result indicated that the transition time evaluatedfrom CPs shown in Fig. 2 can be properly reproduced byassuming the effective diffusion coefficient of U(III) in
the porous Zr layer to be 0.6 ~ 0.8×10-5 cm2/s, which isconsistent with the value 0.7×10-5 cm2/s evaluated fromthe analysis of the longer-term electrorefining experiments [1].

1Central Research Institute of Electric Power Industry
Research Reactor Institute, Kyoto University

2

INTRODUCTION: Analyses of the electrorefining
process for the pyrometallurgical reprocessing of metallic
fast reactor fuel using the multi diffusion layer anodemodel [1] have shown that (a) solubility of UCl3 in
LiCl-KCl melt, and (b) the diffusion coefficient of actinide ions in the porous Zr layer formed at the surface ofthe spent metallic fuel by selective dissolution of the actinides, have great influence on major performance, suchas processing rate and separation between the actinides
and Zr. In this study, chronopotentiometry (CP) was applied to evaluation of these important parameters at
U-9wt%Zr alloy anode.

Current density
1.14 A/cm2
0.76 A/cm2

EXPERIMENTS: Modification of CP theory to beadapted to a situation, where the concentration reaches
saturation by a constant current producing the species
electrochemically, has been reported before [2]. Since
diffusion coefficient of U(III) in LiCl-KCl is known [3],solubility of UCl3 in LiCl-KCl was evaluated using thisdata and τ obtained by CP in this study. After formationof a porous Zr layer by selective anodic dissolution of U
from the U-Zr alloy, CP was performed again. In this step,theoretically, the effective diffusion coefficient of UCl3 in
the porous Zr layer can be estimated using its solubility
data which has been just evaluated in the previous step.
The experimental setup and procedure have been also
reported before [4]. All the experiments were carried out
at 773 K, in a high-purity Ar atmosphere glove box in
KURR hot cell laboratory.

0.57 A/cm2

0.38 A/cm2

Transition time τ

773 K
U in LiCl-KCl : 6.81×10-5 mol/cm3

Fig. 1. Chronopotentiograms obtained with U-Zr
alloy before formation of porous Zr layer.
0

U in LiCl-KCl : 6.81×10-5 mol/cm3, 773 K
Current density : 0.57 A/cm2-0.2

Interval between
measurement

Potential (V vs.Ag/AgCl)

D

RESULTS: The CPs obtained using U-Zr alloy before
the formation of the porous Zr layer are shown in Fig. 1.
The solubility of UCl3 was evaluated to be 0.00449
mol-U/cm3 so that its averaged diffusion coefficient determined from these CPs agrees with the value in literature (1.45 × 10-5 cm2/s) [3]. Subsequently, CPs were
measured after the formation of the porous Zr layer. In
this case, the diffusion coefficient could not be evaluateddirectly from τ value, since the period until diffusion limit of U(III) varied in every measurement even with thesame current density, as shown in Fig. 2. The reason forthis behavior was considered that the decay of UCl3 concentration gradient in the porous Zr layer caused by the
CP measurement requires a long duration due to the expected lower diffusion coefficient and the large thicknessof the layer. Such complicated condition and resulting
behavior in the actual CP measurement cannot be explained using either the basic electrochemical theory [2]-0.4

A > 5 min >B > 20 min >C > 20 min >D > 45 min >E > 85 min > F

A
C

-0.6

E
B

-0.8

F

-1
-1.2
0

20

40

60

Time (s)Fig. 2. Chronopotentiograms obtained with U-Zr
alloy after formation of porous Zr layer.
REFERENCES:[1] M. Iizuka et al., J. Nucl.Sci.Technol., 47 (2010) 1140.
[2] M. Iizuka et al., KURR annual report 2010.
[3] S. A. Kuznetsov, et al., Electrochim. Acta, 51 (2006)
2463.
[4] M. Iizuka et al., KURR annual report 2005.

採択課題番号 26P11-6 乾式再処理に関するウラン化合物を用いた基礎研究（電中研）坂村善治、飯塚政利、魚住浩一、村上 毅（京大・原子炉）藤井俊行、上原章寛、山名 元
58

プロジェクトPR11-7 Electrochemistry and Structural Analysis of Cations in Molten Subhalide Systems:
Fluoride Addition Effect on Voltammograms and UV-vis Spectra of Neodymium Cationin Molten Chlorides
H. Matsuura, A. Nezu, H. Akatsuka, A. Uehara1,
H. Yamana1, T. Fujii1sity was assumed to be the additivity of molar volume ofeach component, and refractive index was temporary
used from the value of KCl due to the non-availability ofthe data of CsCl.

Research Laboratory for Nuclear Reactors,
Tokyo Institute of Technology
1
Research Reactor Institute, Kyoto University

RESULTS and DISCUSSION: Figure 1 shows the differential pulsed voltammograms of cathodic sweeps which
exhibit mainly neodymium reduction peaks. On the contrary to previous measurements[1,2], the potential of neodymium reduction to metal was not shifted positively,
however, drastic negative shift depending on fluoride addition did not occur as well. More strikingly, with increasing fluoride amount, the potenital gap between Nd3+/Nd2+
and Nd2+/Nd decreased, thus disproportionation reaction
may be restricted by addition of fluoride. The variation ofoscillator strength of hypersensitive transition absorptionof neodymium at ca. 589 nm depending on fluoride addition has been evaluated. This absorption peak has been
considered to the indication of coordination symmetryaround neodymium cation, i.e. 6 coordinated octahedral
species, and the smaller value relates to more perfectly
symmetric. One striking feature is that with increasing
fluoride amount until ca. F/Nd = 2 in molten
NaCl-CsCl-NaF, the value of oscillator strength once increases until F/Nd = 2, and decreases rapidly. While inmolten LiCl-KCl-LiF, the value of oscillator strength decreases almost linearly.

INTRODUCTION: Neodymium is the one of the rareearth fission products and was used as the prototype ofsome trans uranium elements due to its similarity of electrochemical behavior. Also, neodymium is one of important materials since it has been widely utilized at magnets
in the motors, and effective recycling technology fromthe end products has been waiting for a long time. Although molten salt should be relatively constructed by asimple structural model due to the predominant ionicspecies in liquid phase, electrochemical behavior has notbeen well understood by the microscopic point of view.
For a recent few years, the electrochemical behavior ofrare earths including neodymium in the molten chlorides
with small amount of fluorides has been focused, andstructural elucidation by extended absorption fine structure and UV-vis spectroscopy of neodymium in molten
salts has been performed [1,2]. In this year, fluoride concentration dependence on the voltammograms of neodymium in molten LiCl-KCl and spectra of neodymium
in molten NaCl-2CsCl was remeasured and the structuralvariation is discussed newly by some parameters derived
from the Judd-Ofelt analysis.

0

EXPERIMENTS: All the electrochemical experiments
using molten salts have been performed in an electric
furnace which is built inside a glove box filled with anargon atmosphere in high purity using an electrochemical
analyzer. Cyclic voltammetry, differential pulsed voltammetry and linear sweep voltammetry have been performed by using the electrodes as follows: working electrode: tungsten, counter electrode: pyrocarbon and reference electrode: silver wire dipped in molten LiCl-KCl
eutectic + AgCl (1 mol%) inside the borosilicate tube,
respectively. Silica glass tube was used as a crucible. To
observe the fluoride addition effect, 0 to 20 times amountof LiF to the concentration of neodymium was added tothe molten salt. All measurements have been performed
at 773 K. UV-vis spectroscopy of neodymium in molten
NaCl-CsCl-NaF at 953 K has been carried out by using
the spectrophotometer. A quartz cell with 10 mm of lightpath was used for the molten salt container, and experimental procedure was exactly the same as that describedin the report of the last year. For the calculation of oscillator strength of the hypersensitive transition and derivation of 2,4,6 parameters by the Judd-Ofelt analysis, den-

x0LiF
x1LiF
x2LiF
x3LiF
x4LiF
x5LiF
x6LiF
x8LiF
x10LiF
x12LiF
x15LiF
x20LiF i [cm-2 A]

-0.5

-1

-1.5

-3

-2.5

-2

-1.5
-

E [V] vs. Cl 2 / Cl

Fig. 1 Differential pulsed voltammograms of cathodic
sweeps of neodymium in molten LiCl-KCl-LiF.
REFERENCES:[1] Y. Shimohara et al, Molten salt chemistry and technology, John Wiley & Sons (2014) 577.
[2] K. Fujita et al, Proc. AMS4, (2012) 264.

採択課題番号 26P11-7

アクチニド元素及び FP 元素含有ハロゲン化物の XAFS 構造解析 プロジェクト
および可視紫外分光研究（東工大・原子炉研）松浦治明、根津 篤、赤塚 洋 （京大・原子炉）上原章寛、山名 元、
藤井俊行
59Polarization Effect of Chloride Ions on Uranyl Ion in Molten LiCl

PR11-8

N. Ohtori, Y. Ishii, A. Uehara1, T. Fujii1, H. Yamana1
Department of Chemistry, Niigata University
Research Reactor Institute, Kyoto University

10

INTRODUCTION: Molten salts are promising solvents for actinides in reprocessing of nuclear fuel. However, knowledge of chemical stability of ionic species inmelts is still inadequate to maximize their potential abilities. Information on local structure around ionic species
in melts may provide useful measures for their stability inmelts. Molecular dynamics (MD) simulation is a powerful tool to elucidate such structures microscopically. In
particular, recent MD simulations with polarizable ionicmodel (PIM)[1,2] have brought much progress in understanding of structure in ionic melts: they have successfully revealed more reliable picture of local structure in
UCl3[2] which is comparable with those from XRD study.
In this work, we have performed MD calculations ofmolten LiCl containing uranyl ion using PIM for chloride
ions, and investigated the effect of polarization of Cl- ionson local structures around uranyl ion.

8

1

g(r)

6

0
1.5

RIM

U=O

1.77 Å

1.80 Å

1.78 Å

1.77 Å

U-Cl

2.73 Å

2.64-2.71 Å

2.78 Å

2.94 Å

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Fig.1 Radial distribution functions for U and Cl pairobtained from the present calculations.

g(r)

2

1

: CPMD
: PIM
: RIM

0
2

3

4

5

6

7

8

9

10

11

r/Å
Fig.2 Radial distribution functions for U and Li pairobtained from the present calculations.

REFERENCES:[1] P. A. Madden, R. Heaton, A. Aguado and S. Jahn, J.
Mol. Struct.:THEOCHEM, 771 (2006) 9-18.
[2] Y. Okamoto, P. A. Madden and K. Minato, J. Nucl.
Mater. 344 (2005) 109-114.
[3] http://www.cpmd.org/

Table 1 Intraionic distance between U and O in uranyl
ion and interionic distance between U and Cl in molten
LiCl containing uranyl ion
PIM

2.0

r/Å

RESULTS: Figures 1 and 2 show radial distributionfunctions for U and Cl pair and U and Li pair, respectively, obtained from the present calculations. Table 1 summarizes intraionic distance between U and O in uranyl
ion and interionic distance between U and Cl which arenear neighbors with each other. These results clearlyshow effects of polarization of Cl- ions on the coordination structures around uranyl ion. That is, we have foundthat PIM can reproduce the results by first-principle MD
simulation better than RIM.

CPMD

4
2

CALCULATION: MD calculations have been carried out using PIM for molten LiCl containing UO22+ ion.
The system included 500, 502, and 1 ions for Li+, Cl-, andUO22+, respectively. MD calculation without polarizationof Cl- ions has also performed, which is referred here to
as RIM: rigid ion model. Furthermore, first principle MD
simulation has been performed using the CPMD code[3]for the system with similar composition but smaller size.
The temperature was set at 1073 K in all the calculations.

Expt.

: CPMD: PIM: RIM

採択課題番号 26P11-8
融体中での f-元素の分子動力学計算と実験系の照合研究 プロジェクト（新潟大・理）大鳥範和、石井良樹 （京大・原子炉）上原章寛、藤井俊行、山名 元

60PR11-9

Study of Isotope Separation of Strontium andCalcium via Chemical Exchange Reaction

R. Hazama, Y. Sakuma1, A. Ito, T. Fujii2, S. Fukutani2, Y.
Shibahara2

0.31
(Sr)

Cation-exchange chro- 25±0.2[7]matography with Sr lactate.
100
LLE with DC18C6.
25
[8]
(Ca)
0.07M CHCl3
36-15
LLE
with
10-50
[9]
(Ca)
HDEHP(di(2-ethylhexyl)
orthophospheric acid)130
LLE with amalgam.
25
[10]
(Ca)
0.27-0.68M Ca/liter Hg
2.3
Ion exchange chromaroom
[11]
(Ca)
tography with Dowex50
temp.
98
CRC(cryptand2B.2.2).
20
[12]
(Ca)
0.01M
CaCl2+CH3OH/CHCl363
CRC (18C6)
20
(Ca)
0.01M
CaCl2+CH3OH/CHCl3
2.8
Iminodiacetate resin
25
(Ca)
0.95M
NaCl+0.05M
CaCl2
56-130CRC (cryptand2B.2.2)-21-21[13](Ca)
CH3OH/CHCl3/H2O
24
CRC (benzo-18C6).
30
[14]
(Ca)
0.02M Ca + 9M HCl
76
CRC (benzo-18C6).
40
[15]
(Ca)
9M HCl (0.8mmφ,1m)
8.9
CRC (benzo-15C5).
50(Ca)
12M HCl (0.8mmφ,1m)
150 *LLE with DC18C6
20
This
(Ca)
0.07M CHCl3
work
Table 1. Unit mass enrichment factors of Sr and
Ca isotope separation.*: Preliminary
REFERENCES:[1]Y. Fujii et al., Z. Naturforsch., 44a (1989) 395.
[2] K. Nishizawa et al., J. Nucl. Sci. Technol., 32 (1995)
1230.
[3] R. Hazama et al., Proc. of 6th Rencontres du Vietnam,
Gioi Publishers (2007) 383: arXiv0710.3840.[nucl-ex].
[4] Y. Fujii et al., Isotopes in Environmental and HealthStudies, Vol. 46, No.2, (2010) 233.
[5] Y. Ban et al., Sep. Sci. Technol. 36(2001)2165.
[6] J. Aaltonen, Suom. Kem., B45 (1972) 141.
[7] T. Oi et al., Sep. Sci. Technol., 27 (1992) 631.
[8]B.E. Jepson et al., J. Inorg. Nucl. Chem.38(1976)1175.
[9]E.P. Horwitz et al., J. Chromatography 125(1976)203.
[10]D. Zucker et al., J. Chem. Phys. 41(1964)1678.
[11] B.E. Jepson et al., Sep. Sci. Technol. 19(1984)173.
[12] B.E. Jepson et al., Sep. Sci. Technol. 25(1990)1893.
[13]K.G. Heumann et al., Angew. Chem. Int. Ed. Engl.
19(1980)406.
[14]K. Hayasaka et al., Prog. Nucl. Energ. 50(2008)510.
[15]S. Nemoto et al., J. Nucl. Sci. Tech. Vol. 49, No. 4,(2012) 425.

Graduate School of Human Environment, Osaka Sangyo
University
1
Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology,
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Anomalous mass dependence wasexperimentally observed in uranium isotope fractionation
by Fujii et al., in the late 80’s[1] and Nishizawa et al.,suggested that odd-even staggering may be due to the
nuclear charge density difference in the middle of 90’s[2]for the case of strontium. Calcium is congener of strontium and easy to handle to check the isotope effects[3,4].
EXPERIMENTS: Isotopic enrichment occurs according
to the following chemical exchange reaction:40
Ca2+(aq) +48CaL2+(org)48Ca2+(aq) +40CaL2+(org) (1)where L represents macrocyclic polyether(18-crown-6).
As a result, 40Ca is enriched in the organic-phase (org)crown solution and the heavy isotopes of 48Ca tend toconcentrate in the aqueous (aq) phase. The mass effect isobserved by the thermal ionization mass spectrometer(TIMS) measurement of calcium isotope ratios for themass range from 40-48 atomic mass unit (amu).
RESULTS: Unit mass enrichment factors of Sr and Ca
isotope separation are summarized in Table 1. In general,a crown ether gives a large separation factor with morethan ten times, compared with an ion exchange method
and has an applicable ability of separation in reality.
Method and system
Temp.
Ref.
ε/△M
-5
(℃)
[×10 ]
51-17
(Sr)

14
(Sr)
5.6
(Sr)
2.3
(Sr)

Liquid-liquid extraction(LLE) with dicyclohexano-18-crown-6(DC18C6).
2.3M-0.5M Sr in aqueous phase.
Crown-ether resin chromatography (CRC). 1.3m
0.1-0.01M Sr + 2M HCl
CRC. 1.3m
0.1M Sr + 3M HNO3α-hydroxyisobutyrate

20±0.5

[2]

35±2

[5]

35±2
Not
specified[6]

採択課題番号26P11-10 ストロンチウム及びカルシウムの化学交換法における同位体分別研究 プロジェクト（大産大院・人間環境）硲 隆太、伊藤彩 （東工大・原子炉研）佐久間洋一（京大・原子炉）藤井俊行、福谷哲、芝原雄司
61

PR11-10 Experimental and Calculated Optical Properties of Molten Alumnium Chloride Melts
T. Goto, K. Hachiya1, A. Uehara2, T. Fujii2, H. Yamana2

cally at 1 : 1-ratio with increasing CsCl content. Our calculation seems to reproduce fluctuations in the structural
rearrangement at that mixing ratio.

Graduate School of Science and Engineering, Doshisha
University
1
Graduate School of Energy Science, Kyoto University
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Molten AlCl3 and ACl-AlCl3 (A:alkaline metals) have been attractive targets of studies
from both fundamental and application viewpoints, because of their relatively low melting points which lead totheir eﬀectiveness. The structure of the melts contains avariety of coordinations which have long been investigated and mainly consists of covalent bonding between
Al-Cl. In this study, Raman scattering measurements are
performed to investigate into their bonding structures,and the spectra are analyzed with ab initio simulations.
We focus our study on CsCl-AlCl3 binary and
LiCl-KCl-CsCl-AlCl3 ternary systems
EXPERIMENTS: Raman scattering spectra obtained
in KURRI were simulated by calculations with GAUSSIAN09 simulation package. Up to 2 ps trajectories of ionsin the melts were calculated with a variant of
first-principle molecular dynamics simulations, ADMP(Atom-centered Density Matrix Propagation). The computations of the ionic trajectories were performed for
CsCl-AlCl3 at 700 K.
RESULTS: As comprehensively reviewed in Ref. [1], up
to 1 : 1 mixture of CsCl/AlCl3 is expected to exclusively
contain AlCl4- cluster as an anion. On the other hand,
Al2Cl7− clusters were contained 9.6% of the total anions
in the whole snapshots, while AlCl4- clusters were 73.4%.
These numbers of anion rates show that AlCl4- clusters
are not always rigid, and Cl- ions are exchanged amongclusters.
Using Einstein relation for the mean square displacements versus time presented in FIG.1, self-diffusion constants were computed to be DCs = 1.216 x 10-4 cm2 s-1,
DAl = 1.530 x 10-4 cm2 s-1 and DCl = 2.671 x 10-4 cm2 s-1,
respectively. As far as we know, there is no direct reference experimental data for this system, while interdiffusion constant for NaCl-AlCl3 mixture were reported to be
4.5 x 10-6 cm2 s-1 at 413 K [2]. The square displacements
for each individual atom are presented in FIG. 2. Al atoms, center of each anion clusters, exhibit both diffusing
and static dynamics. A part of Cl atoms corresponds to Al
atoms, both for two diffusing Al’s and remaining
non-diffusing two. Nevertheless, the rest of Cl’s cannot
be categorized to either of them. This result also supportsthat Cl- ions are exchanged among clusters.
DISCUSSIONS: For CsCl-AlCl3 mixture system, anion structure of isolate AlCl4- tetrahedra shift to corner-sharing two-tetrahedron structure, Al2Cl7− , dramati-

FIG. 1 Mean square displacements versus time for
ADMP dynamics of constituent atoms at 700 K.

FIG. 2 Square displacements versus time for ADMP
dynamics of Cs, Al and Cl atoms at 700 K.
REFERENCE:[1] M. P. Tosi, D. L. Price, M.-L. Saboungi, Annu. Rev.
Phys. Chem. 44 173 (1993).
[2] B. Gilbert, D. L. Brotherton and G. Mamantov J.
Electrochem. Soc. 121 773 (1974).

採択課題番号26P11-11
ｆ－元素の有効利用に関わる基礎及び応用研究
プロジェクト（同志社大・理工）後藤琢也（京大院・エネ科）蜂谷 寛（京大・原子炉）上原章寛、藤井俊行、
山名 元62

PR11-11

Precipitation Behavior of Trivalent Dysprosium Ion by Reaction with Oxide Ion
in CaCl2–LiCl Molten Salt

H. Sekimoto, A. Uehara1, T. Fujii1, H. Yamana2

nm and 2 weak absorption peaks at 918 and at 1121. Figure 2 shows the absorption spectra of Dy3+ in
Li2O-DyCl3-CaCl2-LiCl molten salt. The spectra were
shifted upward and the difference between the top of theabsorption peak and the absorbance on the tangential line
between the feet of the peak at around 1296 nm became
smaller with introducing O2-. These indicates that theformation of DyOCl or Dy2O3(s) proceeded and theamount of Dy3+ in molten salt decreased.

Faculty of Engineering, Iwate University
Department of Materials Science and Engineering
2
Graduate School of Science, Kyoto University4Research
Reactor Institute, Kyoto University
1

0.8

-1

CDy3+ = 0.064 mol kg-1

0.6
Absorbance, A / cm

INTRODUCTION: Development of recycling technique for neodymium magnet is essentially important toachieve sustainable society. Consequently, we propose
and are investigating a new recycling process of neodymium magnet using B2O3 flux [1]. In the process, theneodymium magnet is melted together with sufficientamount of B2O3 in graphite crucible to form molten ironbased alloy, B2O3 slag and Nd2O3-B2O3 slag, which isrecovered and dissolved in molten salt. And then,Fe-Nd-B alloy is produced by electrolysis. For the process, thermodynamic properties such as solubility of rareearth oxide in molten salt is important information. In
this study, precipitation behavior of dysprosium withadding oxide ion in CaCl2-LiCl eutectic molten salt wasinvestigated by spectrophotometry.

-1

CDy3+ = 0.116 mol kg

0.4-1

CDy3+ = 0.157 mol kg

0.2

0.0
800

1000

1200

1400

1600

Wavelength,  / nm

Fig. 1. Flowchart of the recycling process for neodymium magnet proposed in this study.
2.0
1.6
2nd add-1

Absorbance, A / cm

EXPERIMENTS: Solidified samples of CaCl2-LiCl
eutectic molten salt and 5 mol%Li2O-(CaCl2-LiCl)eu.
molten salt were prepared through the following procedure. Li2O, CaCl2 and LiCl was weighted, mixed,
co-melted at 700 °C in cylindrical quartz tube andquenched in Ar atmosphere. 3.01 g of CaCl2-LiCl eutectic molten salt was inserted in a quartz optical cell andmelted at 700 °C. The intensity of the transmitted lightthrough CaCl2-LiCl eutectic molten salt using a tungsten
lamp and a spectrophotometer. Then, adding small
amount of DyCl3 in the CaCl2-LiCl molten salt andmeasuring the intensity of the transmitted light throughDyCl3-(CaCl2-LiCl)eu. molten salt was carried out repeatedly to obtain absorption spectra of Dy3+ at 700 °C.
After that, adding small amount of adding
Li2O-CaCl2-LiCl molten salt and measuring the intensityof the transmitted light through Li2O-DyCl3-CaCl2-LiClmolten salt was also carried out repeatedly to obtain absorption spectra of Dy3+ at 700 °C. Using the data on theintensity of the transmitted light, absorbance was evaluated.

1.2
3rd add

0.8

before0.4

1st add

0.0
800

900

1000 1100 1200 1300 1400 1500 1600
Wavelength,  / nm

Fig. 2. Cyclic voltammogram of CaCl2 molten salt
and CaCl2-Nd2O3-B2O3.

RESULTS: Figure 1 shows the absorption spectra of
Dy3+ in DyCl3-(CaCl2-LiCl)eu. molten salt at 700 C.
There are three absorption peak depending on the concentration of Dy3+ in the range of wavelength,  from
800 nm and 1600 nm; a strong absorption peak at 1296

REFERENCES
H. Sekimoto, A. Uehara, T. Fujii, H. Yamana, KURRI
Progress report, (2012) 102

採択課題番号 26P11-12

吸光分光測定を用いた高温融体中の金属イオンのプロジェクト
溶存形態に関する研究 (f-元素の有効利用に関わる基礎及び応用研究)（岩手大・工）関本 英弘（京大・原子炉）上原 章寛、藤井 俊行、山名 元
63PR11-12

Elucidation of the Uptake Route of Radionuclides in Deciduous andConiferous Trees Using Radio Cesium and Radio Potassium in Annual Tree Rings

T. Ohta, T. Kubota1, Y. Shibahara1, S. Fukutani1 , T. Fujii1
T. Igarashi, Y. Mahara2

the surface soil and did not penetrate deeper into the soil.
The results clearly show that radio-Cs in soil has not
moved from the tree roots to the annual tree rings because the active root system rarely was found in the surrounding surface soil. The high 137Cs concentration in thesapwood zone of konara coincided with the direction of
the arriving radioactive plume in the sampling sites.
Conversely, the concentrations of 137Cs and 134Cs in theannual tree rings of sugi showed non-directionality. As
the radioactive Cs moved from the leaves to the tree
trunk, the directionality of radio-Cs in the annual treerings was eventually disappeared. The results of the present study indicate that 134Cs and 137Cs, detected in thetree rings, from the Fukushima NPP were directly absorbed from the atmosphere by the bark and leaves rather
than the roots. Furthermore, the results suggest that theconcentrations of radio-Cs in the trees in Fukushima
would not further increase in the future.
On the basis of the distribution of radio-Cs in the annual tree rings of the both trees of konara and sugi, we
propose the following guidelines for using contaminatedwood from Fukushima when high concentrations 137Cs
have been detected in the trunk: (1) use the parts of wood
where the 137Cs concentrations are low, and (2) use thehighest parts of the trees as sources of bio-ethanol and/or
biomass, which correspond to the energy sources for the
next generation.

Faculty of Engineering, Hokkaido University
1
Research Reactor Institute, Kyoto University
2
Professor Emeritus, Kyoto University
INTRODUCTION:
Although previous studies have measured the distribution of radionuclides in tree rings, the uptake route of137
Cs originating from the fallouts of nuclear weapon
tests and the Chernobyl accident has undoubtedly argued
the roots1)-4). A number of researchers have also reported
that 137Cs and Pu are absorbed by trees through their barkand leaves; although ambiguously, conclusive evidence
has been presented5).
Understanding the uptake route of radiocesium (radio-Cs) in the annual tree rings is important for a forest
decontaminating in Fukushima. Thus, we investigated thefate of radio-Cs in the Fukushima forestry environment
to understand its uptake route using following method:
the behavior of radiocesium in the soil and the measurements of radiocesium in the annual tree rings of the deciduous tree konara and the coniferous tree sugi by
gamma-ray spectrometry.
EXPERIMENTS
Our experiment is composed three objectives: 1) depth
profile of 137Cs, 134Cs, and 40K in the observed sites, 2)
speciation of radio-Cs in soil, 3) measurement of 137Cs
and 40K in tree rings

REFERENCES:[1] Fesenko et al., Radiat. Environ. Biophys., 40, 105(2001).
[2]Goor and Thirty, Sci. Total Environ., 325, 163 (2004).
[3] Momoshima et al., J. Environ. Radioact., 22, 93(1994).
[4]Kagawa et al., J. Environ. Qual., 31, 2001 (2002).
[5]Kudo et al., J. Environ. Radioactivity, 21, 55 (1993).

RESULTS:The behavior of 137Cs in the soil samples collected in
Fukushima showed the following: (1) radio-Cs in the soil
was primarily absorbed by soil minerals within the top
1-cm-depth from the surface; and (2) 137Cs in soil waswater insoluble and >95% of 137Cs was bound to organicand residual matters. These observations suggest that the137
Cs released from the Fukushima NPP was trapped in

採択課題番号 26P11-13

福島の森林資源有効活用のための樹木年輪放射性核種の プロジェクト
取り込み経路の解明（北大・工）太田朋子、五十嵐敏文（京大・原子炉）窪田 卓見、芝原雄司、福谷 哲、藤井俊行（京都大学）馬原保典
64

Photon Activation Analysis of Alkali Earth Elements and Arsenic

PR11-13with Bremsstrahlung at the KURRI-LINAC
T. Kubota, T. Fujii, S. Fukutani, Y. Shibahara and T.
Ohta1

empirical.

Kyoto University Research Reactor Institute1
Graduate School of Engineering, Hokkaido University

INTRODUCTION: Photonuclear reaction induced byhigh energy photons can produce nuclides that are hardly
produced in a nuclear reactor, for example, neutron deficient nuclides and carrier free isotopes through (γ, n) and(γ, p) reaction, respectively. High energy photon is generated in the bombardment of electrons of 30 MeV to platinum sheets at the KURRI-LINAC. We attempted to
conduct activation analysis for silicate salt in the previous
report [1]. However, Al-29 expected in (γ, p) reaction was
not observed. The results showed the investigation ofeffective reaction cross-sections was required for various
kinds of target samples. In this report alkali earth elements are used as target sample in order to obtain carrier
free alkali metal elements, and in addition the concentration of arsenic in seaweed is evaluated as a preliminary
test instead of neutron activation [2].

Fig. 1. Apparent cross-section for photonuclear reactions; (γ, n), (γ, p) and (γ, np) reaction

EXPERIMENTS: The target samples were once heated to dehydration and disintegrate organic compounds;
alkali earth salts were dried at 100ºC; and seaweed(Hizikia fusiformis) was incinerated at 450ºC. Eachsample was encapsulated in a quartz tube [3]. The tube inan aluminum vessel was irradiated with photon generated
by electron energy of 30 MeV at average current of 200µA for 4 to 48 hours. Radioactivity, A, induced byphotonuclear reaction was measured by γ -spectrometry
and provided the apparent cross-section, θ, which is determined by the following equation:(

A = M 0θ ( µ A ) 1 − e−λt)Fig. 2. Gamma spectrometry of seaweed (Hizikia
fusiformis) irradiated for four hours at the KURRI-LINAC.

where M0, (µA), λ and t were mole number of target nuclide, average electron beam current (micro-ampere),
decay constant, and irradiation time, respectively.

REFERENCES:[1] T. Kubota et al., KURRI PROGRESS REPORT 2013(2014) CO12-5.
[2] R. Ogawa et al., Bulletin of the Faculty of Education,
Ehime University 53 (2006) 131-136.
[3] T. Kubota et al., Recent Advances in Actinide Science,
RSC Publishing (2006) 68-70

RESULTS: Fig 1 shows the apparent cross-sections as
a function of mass number. The cross-section of (γ, n)reaction was larger than that of (γ, p) reaction by one order of magnitude. While the former was the largest at
heavy element, seems to be constant between mass number of 40 to 100. The latter was almost constant independent of mass number. For a light element (γ, np) reaction was also observed; however, its cross-section was
small. The measurement of activated seaweed shows thepeaks of As-74 in Fig. 2. The cross-sections of somephotonuclear reactions were obtained for isotope production and activate analysis, even though these values are

採択課題番号 26P11-14
海水中の放射性核種および重金属の濃度測定（京大・原子炉）窪田卓見、藤井俊行、福谷 哲、芝原雄司（北大・工）太田朋子
65

プロジェクトPR11-14

Study of Applicability of Isotopic Ratio Measurement for Analysis ofRadionuclide in Environmental Samplesespectively. Because of the loading amount of Sr and Cs,
the mass spectra of radioactive Cs and Sr were obtainedwith a secondary electron multiplier detector (SEM).
RESULTS: In the measurement of radioactive Cs,
135
Cs, 136Cs and 137Cs were detected (Fig.1 (a): 134Cs was
not detected, because of the amount generated by theirradiation at KUR. In this measurement, it was observedthat the isotopic ratios of 135Cs/137Cs and 136Cs/137Cs were0.9103±0.0008 and 0.00022±0.00001, respectively. Thesemean that the several ten femto-gram of Cs would be
detectable with the four orders of the significant figures.
In the measurement of radioactive Sr, 89Sr, 90Sr and91
Sr were detected at the measurement 2.6 days later. The
mass spectra of 91Sr and 89Sr were disappeared at themeasurement of 31 days later and 574 days later, becauseof the half-life of 91Sr (T1/2 = 9.5 h) and 89Sr (T1/2 = 50.5d). The obtained isotopic ratios were agreed with resultsof the estimation by using ORIGEN-II code [5]. Thismeans that the several ten femto-gram of Sr would also
be detectable.
It was confirmed that the recovery/analysis method of
Cs and Sr have the applicability for the analysis of radioactive Cs and Sr released on the accident of Fukushima
Dai-ichi Nuclear Power Plant. The loading amount ofseveral pico-grams of radioactive Cs and Sr would bringthe information of the isotopic ratio with the four ordersof significant figure until the ten periods of half-live.

Y. Shibahara, T. Kubota, S. Fukutani, T. Fujii,
T. Shibata1, M. Yoshikawa1
Kyoto University Research Reactor InstituteKyoto University Institute for Geothermal Sciences

Intensity (arb)

INTRODUCTION: For the analysis of radionuclide,the radiation measurement such as γ-spectrometry,
β-spectrometry, and α-spectrometry were mainly performed. Although these methods have been used for themeasurement of radioactive nuclide such as nuclear fuelmaterials and fission products released on the accident ofFukushima Dai-ichi Nuclear Power Plant, they may havedisadvantage in the case of the analysis of radionuclide
having the long half-life and/or that of isotopic composition including naturally occurring isotopes. Because themass spectrometry has advantage for the analysis of theisotopic composition of the elements with high accuracy,
this method may have the applicability for the analysis ofradionuclide released on the accident of Fukushima
Dai-ichi Nuclear Power Plant.
Although the amounts of radionuclide such as radioactive Cs and Sr released on this accident were very huge,
the contaminated environmental samples show the small
radioactivity per unit weight of the contaminated environmental samples, since the contaminated area is very
wide. For the study of the recovery/analysis method of
cesium and strontium, thus, the radioactive Cs and Sr
were generated by the irradiation of natural uranium at
KUR.
EXPERIMENTS: Radioactive Cs and Sr were generated by the irradiation of 10 mg of UO2 of natural uranium at the Kyoto University Research Reactor with theneutron flux for 5.5×1012 n/s cm2. The amounts of the
major radionuclide of Cs and Sr generated by the irradiation for 3 hours were estimated as 7.4×10-11 g (137Cs) and4.5×10-11 g (90Sr). About 2 days later, the irradiated sample was dissolved with 8M HNO3 and heated to dryness.
The residues were immersed in 8 M HNO3 and the insoluble residues were removed by centrifugation. TRU
elements in sample solution were removed by the extraction-chromatography with UTEVA-resin [1], and thesample solution was evaporated to dryness. The residues
was dissolved with 3 M HNO3 solution. After the recovery of Sr by the extraction-chromatography with Sr-resin[2], Cs was recovered by using with ammonium phosphomolybdate (AMP) [3]. The sample solutions for the
analysis of isotopic composition of Sr and Cs were obtained with the dissolving 1 M HNO3 (10μL for Sr, 20 μL
for Cs, respectively).
Isotopic compositions of Cs and Sr were measured
with a TIMS (Triton-T1, Thermo Fisher Scientific). A 1
μL aliquot of each solution was loaded onto a rhenium
single filament with a TaO activator [4]. Loading amountof 90Sr and 137Cs were 4.5×10-12 g and 3.7×10-12 g, re-Intensity (arb)

1

(a)

x10

x10

(b) 134

135

136

x100

137

2.6 days later(89Sr/90Sr=0.79, 91Sr/90Sr=0.012)
2.9 days later(89Sr/90Sr=0.79, 91Sr/90Sr=0.008)
30.8 days later(89Sr/90Sr=0.53)
104.7 days later(89Sr/90Sr=0.20)
573.9 days later(90Sr only)

84

85

86

87

88

89

90

91

Atomic mass [u]Fig.1 Mass spectra of radioactive Cs and Sr. (a) Cs, (b) Sr.

REFERENCES:[1] Y. Shibahara et al., J. Radioanal. Nucl. Chem., 303:
1421-1424 (2015).
[2] T. Kubota et al., J. Radioanal. Nucl. Chem. 303:
39-46 (2015).
[3] Y. Shibahara et al., J. Nucl. Sci. Technol. 51: 575-579(2014).
[4] J. L. Birck, Chem. Geol. 56: 73-83 (1986).

採択課題番号26P11-15 境試料中の放射性核種分析への同位体比分析法の適用の検討 プロジェクト（京大・原子炉）芝原雄司、窪田卓見、福谷哲、藤井俊行（京大・地熱研）柴田知之、芳川雅子
66PR11-15 Tracing Halogen and Noble Gas Recycling in the Northern Izu Subduction Zone by
Neutron Irradiation and Noble Gas Mass Spectrometry
H. Sumino, M. Kobayashi, K. Nagao, R. Okumura1,
S. Sekimoto1 and T. Fujii1

rear-arc magma is consistent with the slab melt contribution inferred from trace element and Pb-Sr-Nd-Hf) isotope compositions [7].
The high I/Cl ratios of the seafloor sediments canaccount for the enrichment of I in subduction fluids relative to sedimentary pore-fluids [1], whereas contributionsof halogens and noble gases from altered oceanic basalts
are limited.
A simple mass balance calculation of Ar isotopes forthe melt generation region beneath the Izu arc revealed
that higher subduction flux of pore water other than directincorporation with its host sediment/crust is necessary,and that serpentinized lithosphere in the subducting slab
is regarded as the best candidate if the hydration of thelithosphere by pore fluids is operating in a closed system.
The significantly smaller contributions of subducted
noble gases and halogens in the Izu arc magmas relative
to those in the mantle wedge peridotites may result froma difference in the P-T condition of the slab in each subduction zone, or from dilution by mantle-derived halogens and He when the subduction fluid induced partial
melting. The former implies a relatively small amount of
the pore-water-derived subduction fluids would be released from a cold slab at a sub-arc depth resulting infurther subduction of halogens, heavy noble gases andpotentially water, to great depths in the mantle, which
account for the seawater-like heavy noble gases observedin the convecting mantle [2].

Geochemical Research Center, Graduate School of Science, University of Tokyo
1
Research Reactor Institute, Kyoto University
INTRODUCTION:
Recent findings of subducted
halogens and noble gases with seawater and sedimentarypore-fluid signatures in exhumed mantle wedge peridotites [1], as well as seawater-derived heavy noble gases(Ar, Kr, and Xe) in the convecting mantle [2], provide
observations that allow us to investigate the processes
that control the return of volatile and highly incompatible
elements into the mantle. To verify whether and how suchsubduction fluids modify the composition of the mantle
beneath subduction zones, we are investigating noble gas
and halogen compositions of olivines in arc lavas from
northern Izu subduction zone and those of seafloor sediments and basalts from NW margin of the Pacific plate. A
combination of neutron irradiation and noble gas mass
spectrometry (NI-NGMS), an extension of Ar-Ar and
I-Xe dating methods, allows us to simultaneously determine trace amounts of halogens with naturally occurring
noble gases by use of ultrahigh-sensitive noble gas mass
spectrometry on neutron-irradiated samples [3,4].
EXPERIMENTS: The samples and standard samples
for NI-NGMS, Hb3gr hornblende and the Shallowatermeteorite were neutron-irradiated for six hours during a 5
MW operation of KUR by using the hydraulic conveyer
to convert halogens (Cl, Br, and I) to corresponding noble
gas isotopes. Noble gases in the unirradiated and irradiated samples were extracted selectively from fluid/melt
inclusions using in vacuo crushing. The evolved noble
gases were analyzed using mass spectrometry at The
University of Tokyo [5,6].

REFERENCES:[1] H. Sumino et al., Earth Planet. Sci. Lett., 294 (2010)
163-172.
[2] G. Holland and C.J. Ballentine, Nature, 441 (2006)
186-191.
[3] G. Turner, J. Geophys. Res., 70 (1965) 5433-5445.
[4] J.K. Böhlke and J.J. Irwin, Geochim. Cosmochim.
Acta, 56 (1992) 187-201.
[5] N. Ebisawa et al., J. Mass Spectrom. Soc. Jpn., 52(2004) 219-229.
[6] H. Sumino et al., J. Mass Spectrom. Soc. Jpn., 49(2001), 61-68.
[7] J.-I. Kimura et al., Geochem. Geophys. Geosys., 11(2010) Q10011.

RESULTS: MORB-like 3He/4He and halogen ratios of
the olivines indicate insignificant contributions to the Izu
arc magmas of radiogenic 4He and sedimentary-pore-fluid-like halogens, both of which are observedin the subduction fluids released from a slab at a depth of
100 km [1]. On the other hand, a clear difference in40
Ar/36Ar ratios between the Izu volcanic front and reararc, and a comparison with those of the seafloor sediments and altered oceanic crusts suggest that Ar of sedimentary pore-water origin in the subducting slab or hydrated layer of the mantle wedge is liberated continuously with depth and that it affects the noble gas compositionof the magma generation region significantly. A small
addition of the sediment-derived noble gases to the

採択課題番号 26P11-16

希ガス化法を用いた極微量ハロゲン測定による地球深部の水の起源の解明（東大院・理・地殻化学実験施設）角野浩史、長尾敬介、小林真大（京大・原子炉）藤井俊行、関本 俊、奥村 良
67

プロジェクトPR11-16

Volcanic and Tectonic History of Philippine Sea Plate (South of Japan)
Revealed by 40Ar/39Ar Dating Technique

O. Ishizuka, T. Fujii1, R. Okumura1, S. Sekimoto1

IBM arc). However, due to the paucity of geologicaland geophysical data from these basins, their origin
and history are yet unclear.
YK10-14 and YK13-08 cruises by R/V Yokosuka
investigated Palau Basin) and southern part of West
Philippine Basin obtained crucial geological and geophysical data [2] for reconstruction of the Philippine
Sea Plate. 12 dredge hauls and 4 Shinkai submersible
dives were made during these cruises. 40Ar/39Ar datingof dolerite sample from the Palau Basin crust exposedat the Mindanao Fracture Zone at c. 130oE gave aplateau age of 40.4 Ma. This result implies that the
spreading of the Palau Basin was still going on at 40.4
Ma. This age is within an age range of active spreading of the West Philippine Basin.
This year we conducted 40Ar/39Ar dating of basaltic
samples from 2 locations in the eastern part of the basin
along the Mindanao Fracture zone. Fig. 1 shows age
spectra for the 2 analyses. Sample 6K1358R11, which
was collected by Shinkai 6500 at 4564 m deep gave aplateau age comprising of 63.8% of released gas.
YK10-14 D3R14, which was collected further east along
the Mindanao Fracture Zone by dredging also gave awell-defined plateau comprising of 96.3% of released gas.
The plateau ages shown here are still temporary age because flux monitor measurement has not been completed
yet. However, these data strong imply that the age offormation of the Palau Basin closely matches with that ofWest Philippine Basin, and this result is crucial for tectonic reconstruction of this area. Final ages will also allow us to determine the direction and rate of seafloor
spreading when the Palau Basin formed.

Geological Survey of Japan, AIST
1
Research Reactor Institute, Kyoto University
INTRODUCTION:
Submarine volcanic rocks are
known to give ages different from their true eruption ages
in some cases. This is due to the existence of excess 40Ar
in the rapidly quenched glass or Ar loss and K remobilization caused by reaction with seawater or hydrothermal
fluids. Stepwise-heating analysis in 40Ar/39Ar dating isparticularly useful for dating submarine volcanics.
	  Since this is the first time to use KUR for our laboratory, we investigated neutron flux gradient and production of interfering isotopes for 40Ar/39Ar method by irradiating standard minerals and synthetic glasses as preparation for dating of unknown samples.
EXPERIMENTS: Samples were wrapped in an aluminum foil packet and the packets were piled up in a purealuminum (99.5% Al) irradiation capsule (9 mm diameterand 30 mm long). The irradiation capsule was partitioned
into 3 compartments to minimize the uncertainty of thesample positions at irradiation. The irradiation capsulewas wrapped with 0.5 mm-thick Cd-foil before irradiation. The capsule was irradiated 2 hours at 5MW in Hyd
facility of KUR. Analyses were conducted using
40
Ar/39Ar geochronology facility at the Geological Surveyof Japan/AIST following the analytical procedure described in [1].
For the experiments described here, around 15 mg ofsample was analyzed in each analysis. Due to alterationof poorly-crystallized part groundmass, basaltic samples
were treated at 100oC on hot plate with stirrer in 6N HCl
for 60 minutes and then 6N HNO3 for 60 minutes to remove possible alteration products (clays and carbonates)
prior to irradiation. This procedure effectively separated
and concentrated fresh plagioclase in groundmass and of
microphenocryst. After this acid treatment, these separates were examined under binocular microscope before
packed for irradiation.
RESULTS: Two basaltic samples recovered fromthe northern margin of the Palau Basin, southernmost
part of the Philippine Sea plate, were studied. The West
Philippine Basin and Palau Basin are supposed to havebeen the oldest oceanic basins in the Philippine Sea Plate.
Accordingly, their origin and growth history can be a
critical constraint on the tectonic reconstruction of thePhilippine Sea Plate. These basins could have existed
prior to the Izu-Bonin (Ogasawara)-Mariana arc (IBMarc), or formed as a consequence of subduction initiation along the IBM arc (e.g., backarc basins of the

採択課題番号 26P11-17	
 Fig. 1 Age spectra for the basalts from the Palau Basin.
REFERENCE:[1] O. Ishizuka et al., Chem. Geol., 266 (2009), 274-296.
[2] Sasaki, T., Yamazaki, T., Ishizuka, O., (2014) Earth
Planet. Space, 66:83, doi:10.1186/1880-5981-66-83.

40

Ar/39Ar 年代測定による日本周辺海域の火山活動史及びプロジェクト
地殻構造発達史の解明	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 	
 

（産総研）石塚	  治（京大・原子炉）藤井	  俊行、奥村	
 良、関本	
  俊	
 
	
 

68

PR11-17

Ar–Ar Age Determination of Minamitorishima

N. Hirano, H. Sumino1, T. Fujii2, R. Okumura2, S.
Sekimoto2

stead of 40K, were simultaneously analyzed using a
mass-spectrometer with an extraction technique of multi-step heating of approximately every 50 to 100 °C between 500 to 1500 °C.

Center for Northeast Asian Studies, Tohoku University
1
Geochemical Research Center, Tokyo University
2
Research Reactor Institute, Kyoto University

RESULTS: The irradiations of sample in KUR weredone in May, 2014. We are going to analyze the irradiatedsamples after cooling. We note that the Minamitorishima
is just only “island” in WPSP in spite of many of larger
volcanic edifices of seamount and guyot thanMinamitorishima. We have a hypothesis of different process and age to make the island in WPSP, awaiting future
analytical results

INTRODUCTION: Most of seamounts on the western
Pacific Plate formed before 70 Ma in the so-called West
Pacific Seamount Province (WPSP) which is characterized by relatively short seamount chains maybe indicating a significant short-lived hotspot system [1]. The geochronological studies of each Cretaceous seamount, on
the other hand, show the long-lived main shield stage ofvolcanism, because a seamount remained above a hotspot
for a long time (approximately 10 m.y. [2]). This may be
attributed to either of the following two possibilities: 1)
An abundant heat supply as in the superplume episode in
the Early Cretaceous [3][4][5]. 2) Slow absolute motionof the Early Cretaceous Pacific Plate (3–6 cm/yr.) [6][7].
The research cruise using R/V Yokosuka equippedwith the submersible SHINKAI 6500, was conductedaround the Minamitorishima Island on May 2010 in orderto know the detail history during the formation of theisland, where volcanic rock samples have never beenobtained before (Fig. 1). The shipboard multibeam
acoustic surveys showing the detail bathymetry discovered the volcanic cones on seamount slope and the clusters of small conical volcanoes on surrounding abyssal
plain (Oikawa and Morishita, 2009). Most of cones areseveral hundred meters in height and 1–10 km in diameter. We observed the stratigraphy of Minamitorishimausing the submersible SHINKAI 6500. Highly vesicularlavas were sampled at the volcanic cone on the seamountslope. The olivine-bearing dense lavas, on the other hand,were obtained at the steep slope beneath the lava platformin bathymetry, implying main-shield stage lavas in contrast to volcanic cones probably erupted at the rejuvenated stage during the Minamitorishima’s formation.

Fig. 1. Bathymetric map of Western Pacific.
REFERENCES:[1] A. A. P. Koppers et al., Geochem. Geophys. Geosyst.,
4 (2003) DOI | 10.1029/2003GC000533[2] N. Hirano et al., Marine Geol., 189 (2002) 371-379.
[3] K. G. Cox, Nature, 352 (1991) 564-565.
[4] R. L. Larson, Geology, 19 (1991) 547-550.
[5] R. L. Larson and C. Kincaid, Geology, 24 (1996)
551-554.
[6] R. A. Duncan and D. A. Clague, in The ocean basins
and margins, 89-121 (New York, Plenum, 1985)[7] J. W. Henderson et al., Tectonics, 3 (1984) 121-132.
[8] I. McDougall and T. M. Harrison, in Geochronology
and Thermochronology by the 40Ar/39Ar Method,(Oxford, New York, 1988).
[9] N. Iwata, Ph.D. Thesis, Tokyo Univ. (1998).
[10] K. Saito, Sci. Rep. Res. Inst. Tohoku Univ. (RITU),
Japan A40 (1994) 185-189.

EXPERIMENTS: Radiometric Ar-Ar dating is commonly used to determine the ages of submarine lavas,
because the traditional K-Ar dating is impossible to remove the alteration part in such rocks [8]. The
rock-samples prepared for dating were crushed to100-500 μm grains, and leached by the 1N HNO3 at
70-60 °C for one hour. The leached samples were irradiated by neutrons in a reactor to produce 39Ar from 39K
during a few hours. During the irradiation, samples were
packed with EB-1 biotite flux monitors [9], K2SO4 and
CaF2 as correcting factors in an aluminum capsule. They
are shielded by Cd foil in order to reduce neutron-induced 40Ar from 40K [10]. Then, radiogenic 40Ar,
daughter nuclide of radioactive 40K and parent, 39Ar in-

採択課題番号 26P11-18 新種の火山のメカニズムを解明するための 40Ar/39Ar 年代測定 プロジェクト（京大・原子炉）藤井俊行、関本俊、奥村良（東大院・理・地殻化学実験施設）角野浩史、（東北大・東北アジア研究センター）平野直人
69