1A01 Measurement of the excitation functions of Np isotopes in U+p and Th+Li reactions.
HAYAKAWA, Y.1, SAKAGUCHI, A.2, MURATA, M.1, MATSUMURA, N.1, FUJINUMA, S.2,
NAKAJIMA, A.2, KASAMATSU, Y.3, SHINOHARA, A.3, KOMORI, Y.4, YOKOKITA, T.4,
MORI, D.4, YANOU, S.4, HABA, H.4, YOKOYAMA, A.1(1Kanazawa University, 2University of Tsukuba, 3Osaka University, 4RIKEN)
A naturally occurring nuclide, 237Np (t1/2 = 2.1×106y), is analyzed by using a short-lived Np
isotope or a Pu isotope considered similar in a chemical behavior, but there is no tracer that ismore satisfactory in its determination. Because 236gNp (t1/2 = 1.5×105 y) is long-lived and can beapplied to Accelerator Mass Spectrometry (AMS), it has been a candidate as a tracer for
determination of Np for years. However, no production method has been established for the
nuclide. In this study, nuclear reactions of U + p and Th + Li were carried out to produce Np
isotopes and their yields were measured by γ-ray spectrometry and AMS. It was found that the234

Np, 236gNp 236mNp and 237Np nuclides are produced in the reactions. Compared to the U + p

reaction, cross sections of Np isotopes in the Th + Li reaction are smaller, while m/g ratio of 236Np
is more favorable than U + p reaction. In this paper, in addition to m/g ratio, the formation ratioof Np-237 to Np-236g is also discussed.
1A02 Measurements of Excitation Functions for the natW(d,x) Reactions and Half-lives ofRhenium Isotopes
KOMORI, Y.1, MURAKAMI, M.1,2,3, HABA, H.1(1RIKEN Nishina Center, 2Grad. School of Sci. and Technol., Niigata Univ., 3JAEA)
We are conducting model experiments for chemical studies of element 107, Bh, using longlived radiotracers of its homolog, Re: 183Re (T1/2 = 70 d) and 184mRe (T1/2 = 169 d). In this work,
excitation functions of deuteron-induced nuclear reactions on natural tungsten have beenmeasured up to 24 MeV for the quantitative production of these Re isotopes. The target stack of
W/Ti foils was irradiated for 1 h with a 24-MeV deuteron beam supplied from the RIKEN AVF
cyclotron. After the irradiation, each foil was subjected to γ-ray spectrometry. The beam currentof 0.18 µA was determined by the monitor reaction natTi(d,x)48V. In this work, we could measure
the excitation functions for the production of 181,182a,182b,183,184m,184g,186gRe, 187W, and 182g,184Ta in thenatW(d,x) reactions. We discussed them by referring to the previously reported data and thetheoretically evaluated data in the TENDL-2017 library. Thick-target yields for the investigatedisotopes were also deduced from the measured excitation functions. Through the radioactivity
measurements, we noticed that the half-lives of some Re isotopes such as 181,183Re are slightly

shorter than those adopted in the current nuclear database. Therefore, we precisely measured theirhalf-lives in the separate experiments. We found that the half-lives of 181,183Re and 184mRe arealmost 5% shorter and longer than those in the current database, respectively.

1A03 Production of p-nuclei in the Ia supernova
KINOSHITA, N.
(Shimizu Co.)
Thousands of nuclei are synthesized in tens milliseconds under extremely high temperatureand pressure which are achieved by supernovae and neutron star mergers. The nuclides aresynthesized in a complicated network of nuclear reactions by photon, neutron, proton, alphaparticles, and decay. The p-nuclei, neutron deficient nuclei which are not produced by a neutron
capture reaction, are mainly synthesized by Ia supernovae (IaSN). Thousands of reaction rates of
the nuclear reactions depend on theoretical model, although several nuclear reactions for thesynthesis are experimentally confirmed. In the present work, I performed the network calculationof the nucleosynthesis in the supernova condition obtained by the W7 model using the reaction
rates calculated with different parameters for the optical model and level density in the HauserFeshbach calculation. Production yields of the p-nuclei showed different feature regardless of thenuclear model. The mixing of the products synthesized in supernovae with a different Pb/Fe ratio
would be required for the explanation of solar abundance. On the other hand, 98Tc/96Ru and146

Sm/144Sm ratio produced in the supernovae were at least tens times larger than the abundancesin the primitive solar system.

1A04 Simultaneous Production and Separation of Carrier-free Alkali Metal Tracer Using
Photonuclear Reaction
IKEDA, H.1,2, KIKUNAGA, H.2, WATABE, H.1(1Cyclotron and Radioisotope Center, Tohoku University, 2Research Center for Electron Photon
Science, Tohoku University)
The demand for carrier-free RI tracers is increasing to understand the behavior of alkali metals
in plants. In Japan, when performing experiments using K tracer, it has to be produced by anaccelerator each time. If other alkali metal tracers can be produced simultaneously with the K
tracer, efficient experiments can be performed in time and economy. In this study, the conditions
for simultaneous production and separation for carrier-free mixture RI tracer of K, Rb and Cs
were determined and demonstrated.

The CaO, SrO and BaO pellets in a quartz tube were irradiated with bremsstrahlung radiation.
Water and oxalic acid (H2C2O4) solution were added to the irradiated target to precipitate. The
supernatant was separated by centrifugation and it was charged to a cation exchange column (2mL). The column was flushed with 20 mL of 0.01 M HCl. It was eluted with concentrated (11.5
M) HCl to create elution curves.
12% of K-43, 15% of Rb-86, and 9% of Cs-136 were coprecipitated with oxalate (mixture of
CaC2O4, SrC2O4 and BaC2O4). Most of the alkali metal was eluted with about 4.0 mL ofconcentrated HCl. We demonstrated that carrier-free mixture RI tracer of K, Rb and Cs can beproduced and separated simultaneously.

1A05 Production of At-211 at RIKEN
WANG, Y., SATO, N., KOMORI, Y.,YOKOKITA, T., MORI, D., USUDA. S., HABA, H.
(Nishina Center for Accelerator-Based Science, RIKEN)The 7.214-h half-life radioisotope 211At offers many potential advantages for targeted αparticle therapy. We developed a production technology of 211At at the RIKEN RI Beam Factory
to distribute this useful radioisotope to the researchers in Japan. A 29-MeV alpha beam was
extracted from the RIKEN AVF cyclotron. After passing through a Be vacuum window and He
cooling gas, the energy on the target was about 28 MeV. 211At was produced via the209

Bi(α,2n)211At reaction by irradiating a metallic Bi target for 2 to 8 hours at beam intensities

between 2 and 16 pµA. The irradiated Bi target was measured using a Ge detector, and the thicktarget yield (TTY) agreed well with the literature data. 211At was separated from the irradiated Bi
target by a dry distillation technique in a quartz column (850 ℃) with O2 carrier gas (10 mL/min).
The separated 211At was dissolved with chloroform, and was dried up by a N2 gas flow (100mL/min) at a room temperature. The typical chemical yield was about 80%.

1A06 Development of thermochromatography apparatus for accurate measurement ofadsorption temperature of At compound in gas phase
ICHIMURA, S., OBATA, H., NAKAGAWA, S., TERAMOTO, T., OOE, K., NAGATA, K.,
TOYOSHIMA, A., YOSHIMURA, T., SHINOHARA, A.
(Osaka Univ.)
We have been developing a thermo-chromatography apparatus to separate and identify At
compounds produced by dry distillation. In our previous study, accuracy was insufficient in thecolumn temperature and the deposition position of 211At for the apparatus. In the present study,

we improved the apparatus to solve the accuracy problems; temperature stability is largely
increased by using 10 independent heaters and adsorption position of 211At can be precisely
determined with an automated CdTeZn detector with a 2-mm collimator. In an experiment, 211At
was produced via the 209Bi(α, 2n)211At reaction. The target was set in a quartz column and washeated to 850° C with flowing mixed helium/oxygen gas (3:1) at a rate of 20 ml/min, while thethermo-chromatographic column connected to the distiller had a temperature gradient. Then, thegamma-ray was measured with the detector to determine adsorption position of 211At. As a result,
3 peaks of 211At were observed over the temperature range between 100 and -80 oC, which isqualitatively consistent with our previous study. However, the adsorption temperature of theobserved peaks was different from that in the previous study. Detail of the results will be presented
in the symposium.

1A07 Experimental and computational study of nitrato complex of Zr, Hf, and Th - toward
the chemical study on Rf
WATANABE, E.1, HAYAMI, S.1, TONAI, K.1, NINOMIYA, H.1, KASAMATSU, Y.1,
KITAGAWA, Y,2, SHIGEKAWA, Y.3, YOKOKITA, T.3, NAKANO, M.2,4, SHINOHARA, A.1(1Graduate School of Science, Osaka Univ., 2Graduate School of Engineering Science, Osaka
Univ., 3Nishina Center, RIKEN, 4Institute for Molecular Science)
We are interested in the chemical properties of element 104, Rf. We aim to conduct anionexchange experiments of Rf in nitric acid using the automated solid-liquid extraction apparatus
for online use (AMBER), and to obtain the distribution coefficients in ion exchange equilibrium.
As preliminary experiments, we have previously conducted anion-exchange experiments in nitricacid by a batch method using radioactive tracers of Zr, Hf, and Th, which form tetravalent ions in
an aqueous solution same as Rf, and it was found that the ion exchange reaction equilibrium with
Adogen 464 resin is rapidly reached. In this presentation, we used the radioactive tracers of Zr,
Hf, and Th to optimize the conditions in the extraction using AMBER; for example, the conditions
for back extraction from the resin. Furthermore, we tried to identify and understand chemical
species present in nitric acid solution by DFT calculation. Analysis of the molecular orbitals of[Th(NO3)6]2-, which is stably present in nitric acid, suggested that the 5f orbitals of Th partly
participate in the bonding orbital between Th and NO3-. In addition, it was suggested that Th ion
prefers neutral or anion complexes coordinated by 4 or more nitrate ions, while Zr is moststabilized when two nitrate ions are coordinated.

1A08 Anion exchange of Rf in H2SO4YOKOKITA, T.1, KASAMATSU, Y.2, WATANABE, E.2, KOMORI, Y.1, NINOMIYA, H.2,
WANG, Y.1, MORI, D.1, GHOSH, K.1, SHINOHARA, A.2, HABA, H.1(1RIKEN, 2Osaka Univ.)
It is difficult to obtain distribution data at equilibrium for the short-lived 261Rf in 2-phase
distribution, but such data are necessary to discuss in detail the chemical properties of Rf. To
obtain distribution coefficients (Kd) of Rf, a batch-type solid-liquid extraction apparatus(AMBER) was developed. In this work, to study the sulfate complexation of Rf, we performed
an anion-exchange experiment of Rf in H2SO4 by using AMBER.
261

Rf and 169Hf were produced in the 248Cm(18O,xn)261Rf and natGd(18O,xn)169Hf reactions,

respectively, by using the AVF cyclotron at RIKEN. The products were transported from the target
chamber to AMBER with a He/KCl gas-jet system. We performed anion-exchange experimentsof 261Rf and 169Hf by using AMBER. After the anion exchange, we measured α-particles for the
samples by using an automated rapid α/SF detection system.
We obtained the Kd value of Rf at 0.1 M H2SO4. The Kd value of Rf is clearly lower than thoseof Zr and Hf and agrees with those of Th. This result suggests that Rf does not form an anionicsulfate complex at 0.1 M H2SO4, though there is a possibility that a counter ion of HSO4− ispreferentially adsorbed on the resin. To clarify the formation of the anionic sulfate complex of Rf
in this studied condition, further experiment of Rf is required at low HSO4− concentration.
1A09 Coprecipitation experiments of element 102, No, with Sm hydroxide with NH3 andNaOH aqueous solutions.
HAYAMI, S.1, NINOMIYA, H.1, WATANABE, E.1, SHIGEKAWA, Y.2, NAGASE, M.1,
KASAMATSU Y.1, KONDO, N.1, HABA, H.2, YOKOKITA, T.2, KOMORI, Y.2, MORI, D.2,
WANG, Y.2, GHOSH, K.2, SATO, N.2, SHINOHARA, A.1(1Grad. Sch. of Sci., Osaka Univ., 2RIKEN Nishina center)
Nobelium with atomic number 102 is one of actinide elements. It is reported that stable
oxidation state of No is +2 although those of other heavy actinide elements are all +3. The
chemical behavior of No is reported to be similar to that of Group 2 elements. However, it isdifficult to investigate the chemical properties of No because of the low production rates and shorthalf-lives. In this study, by applying the samarium hydroxide coprecipitation method, we
performed online coprecipitation experiment of 255No using semi-automated coprecipitationequipment. We produced 255No in the 248Cm(12C, 5n)255No reaction with the AVF cyclotron at

RIKEN. We determined the coprecipitation yields of No in dilute or concentrated aqueous NH3
or 0.10 or 1.0 M NaOH solutions with the measurement of α-particles using automatic α-particle
measurement system. As a result, the coprecipitation behavior of No in low hydroxide ion
concentration differed from that of Group 2 elements. The No yields in high hydroxide ion
concentrations are close to those of Ca.

1A10 Measurement of half-lives and internal-conversion electron energy spectra for U235m oxide, fluoride, and chloride
SHIGEKAWA, Y.1, KASAMATSU, Y.2, YAMAKITA, Y.3, KANEKO, Y.4, WATANABE, M.4,
WATANABE, E.2, YASUDA, Y.2, KONDO, N.2, SHINOHARA, A.2(1RIKEN Nishina Center, 2Graduate School of Science, Osaka University, 3Graduate School ofInformatics and Engineering, The University of Electro-Communications, 4JAEA)As 235mU has extremely low excitation energies, the nucleus interacts with an outer-shellelectron in the internal conversion (IC) process. Therefore, the half-life of 235mU varies dependingon the chemical environment. We have been aiming to elucidate the deexcitation process of 235mU
by measuring IC electron energy spectra in addition to half-lives for various chemical
environments. In this study, half-lives and energy spectra for 235mU oxide, fluoride, and chloride
were precisely measured using a retarding-field magnetic bottle electron spectrometer. 235mU
oxide was prepared by collecting 235mU ions recoiling out of a 239Pu source on the surface of a Cu
foil; 235mU fluoride and chloride were prepared by subjecting 235mU collected on the surface of Cu
foils to HF gas and HCl gas, respectively. With the help of the magnetic bottle spectrometer, thehalf-life and energy spectrum for 235mU chloride were obtained for the first time, and those for235m

U oxide and fluoride were measured with higher S/N and energy resolution than before. The

measured energy spectra allowed for estimating molecular orbital diagrams corresponding to the235m

U samples. Comparison between the molecular orbitals diagrams and measured half-lives

successfully showed that the half-life variation of 235mU dominantly originates from 6p orbital
variation.

1A11 Observation of the internal conversion electrons emitted from Th-229m throughcoincidence measurement between beta particles and electrons from Ac-229
SHIGEKAWA, Y.1, KASAMATSU, Y.2, WATANABE, E.2, YASUDA, Y.2, KONDO, N.2,
HAYAMI, S.2, NINOMIYA, H.2, HABA, H.1, SHINOHARA, A.2(1RIKEN Nishina Center, 2Graduate School of Science, Osaka University)

The excitation energy of 229mTh is only around 8 eV; thus, the decay mode and half-life of229m

Th are expected to vary depending on chemical environments. The internal conversion (IC)electron of 229mTh was recently observed and the half-life of 229mTh on the Ni-alloy surface wasfound to be around 7 µs; however, half-lives for other chemical environments have not beenreported. In order to measure half-lives of 229mTh for various chemical environments in the future,
we tried to measure IC electrons of 229mTh through coincidence measurement between beta
particles and electrons from 229Ac. Due to the low recoil energy in the beta decay of 229Ac, thechemical environment of 229mTh can be controlled by controlling that of 229Ac. First, we fabricated229

Ac through proton irradiation of a 232Th target. Then, we chemically purified 229Ac and prepared

an electrodeposited 229Ac source. We measured the detection times of beta particles and electrons
from the source, and constructed coincidence spectra. The prepared 229Ac source was found toinclude only Ac isotopes, showing that the chemical purification process was successfully
performed. In a coincidence spectrum, we successfully observed a decay curve (half-life 10.2 ±7.8 µs) corresponding to the IC electrons of 229mTh.

1A12 Quantitative evaluation of DNA double strand break caused by radiations withdifferent LET
WADA, T.1, NAKATA, M.1, KOIKE, A.1, YAMAZAKI, S.1, ZHAO, M.1, SUN, F.2,
SHIMOYACHI, H.3, HATANO, Y.3, KENMOTSU, T.4, OYA, Y.1(1Graduate School of Integrated Science and Technology, Shizuoka University, 2Faculty of
Science, Shizuoka University, 3Hydrogen Isotope Research Center, University of Toyama,
4

Faculty of Life and Medical Sciences, Doshisha University)
Since the accident of Fukushima Daiichi nuclear power plant, people are concerned withbiological effects by radiation especially damage caused by β-rays from tritium, which containedin polluted water in Fukushima power plant. The radiation effect for DNA is different among
various radiations with different linear energy transfer (LET) values. In the present study, theeffect of radiation with various LET values on genome-sized DNA double strand breaks (DSBs)
was quantitatively evaluated using several types of radiation sources. The DNA of bacteriophage(T4 GT7: 166 kbp) was exposed to various radiation sources (45Ca, 60Co, etc.) with similar doselevel (0.50–25 Gy). After fluorescently dyeing procedures for DNA, the length of DNA molecules
was evaluated by single-molecule observation method using fluorescence microscope. A number
of DSBs were calculated quantitatively. As a result, 45Ca caused larger number of DSBs than 60Co.
It is plausible that high concentration of radicals induced by γ-ray (60Co) irradiation enhanced

recombination of radicals, and the recombination led to the suppression of DSBs compared withthat of β-ray (45Ca) irradiation. This is because the dose rate of irradiation was quite different
between 60Co (50 Gy/h) and 45Ca (2.0×10-2 Gy/h). Due to this big difference, a dose rate hadstronger influence on DSB rate than LET.

1A13 Correlation measurement of precision mass and decay properties of 207Ra with
MRTOF + α-TOF.
NIWASE, T.123, WADA, M.3, SCHURY, P.3, ITO, Y.4, KIMURA,S.2, KAJI, D.2, ROSENBUSCH,
M.2, WATANABE, Y, X.3, HIRAYAMA, Y.3, MIYATAKE, H.3, MOON, J, Y.7, ISHIYAMA, H.2,
MORIMOTO, K.2, HABA, H.2, TANAKA, T.8, SHIZAWA, S.523, TAKAMINE, A.2, MORITA,
K.12, WOLLNIK, H.6(1Kyushu Univ., 2RIKEN, Nishina Center., 3KEK., 4JAEA., 5Yamagata Univ., 6NMSU., 7IBS.,
8

ANU.)
The atomic mass is a unique quantity for each nuclei. Therefore, precision mass measurement

allows us to identify the atomic number as well as the mass number of the nuclide. Recently, wedeveloped a novel detector as named “α-TOF” for precision mass measurement of superheavy
nuclei with multi-reflection time-of-flight mass spectrograph(MRTOF-MS). The α-TOF detector
is capable of performing correlation measurement of time-of-flight signal and successive α decay
signal. It can reliably discriminate true events from background events.
The first online experiment of the α-TOF detector was performed at SHE-Mass-II coupled withthe gas-filled recoil ion separator GARIS-II and MRTOF-MS. A short lived radium isotope 207Ra
was produced in the 159Tb(51V,3n) reaction. The reaction products(evaporation residues : ERs)
were in-flight separated from the projectiles and some other background products. The ERs wascaptured and thermalized in a cryogenic gas-cell. The thermalized ions were extracted by using
the rf-carpet and transported to MRTOF-MS via multiple ion traps.
As a result of the experiment, the time-of-flight and correlated accompanying decay signals
were successfully measured. By correlating with disintegration events, we confirmed that only
true events can be distinguished even in high background environments.

1A14 Identification of Atomic Number for Heavy Elements by Bragg Curve Measurement
FUJITA, K., NIWASE, T., SHIRASAKA, K., SUEKAWA, Y., MORITA, K.
(1Kyushu Univ., 2RIKEN Nishina Center)
A direct measurement of the atomic number is demanded for the experiments of the superheavy

nuclei synthesis such as 119th element search, since the conventional method of analyzing thealpha-decay chain have a limitation of identification for spontaneous-fission nuclei. We havedeveloped a Bragg curve detector(BCD) employing a digital signal processing technique toimprove the separation efficiency especially for low-energy superheavy ions. Although the heightof Bragg peaks induced by heavy ions of less than 1.5 MeV/u are not proportional to the incident
energy, the waveform analysis makes it possible to identify the nuclei having the different atomic
number.
The performance test of the developed detector was performed at Kyushu University Center
for Accelerator and Beam Applied Science. The heavy ion beams supplied from the Tandem
accelerator were scattered and injected to the BCD. The measured waveforms of the BCD wellmatched to the simulation results using Garfield++ with a field map obtained from Gmsh andElmer. A sufficiently high separation efficiency was achieved at the same energy particles withdifferent atomic number.

1A15 Development of an atomic beam source using a high-temperature nozzle type cavity foratomic beam generation of superheavy elements
TOMITSUKA, T.1,2, SATO, T. K.1,3, ITO, Y.1, TOKOI, K.1,3, SUZUKI, H.1,3, ASAI, M.1,
TSUKADA, K.1, GOTO, S.2, NAGAME, Y.1(1ASRC, JAEA, 2Graduate School of Science and Technology, Niigata Univ., 3Graduate Schoolof Science and Engineering, Ibaraki Univ.)
To study atomic properties of superheavy elements, we have been developing an Atomic Beam
Source apparatus (ABS) with a high-temperature nozzle type cavity coupled to the He/CdI2 gasjet transport system. Configurations of a nozzle-type cavity for effective extraction of thermal
atomic beams have been examined using Monte Carlo simulation, and off-line extraction
experiments with stable isotopes have been conducted. According to the simulation, large
amounts of atomic beams get out of the inlet of the nozzle cavity. Thus, to avoid escaping beams
from the inlet, we need to minimize the inlet diameter of the nozzle cavity. Here, we have
implemented an aerodynamic lens (AL) to the ABS to reduce the loss of atomic beams from theinlet of the cavity. The AL consists of three lens orifices and four spacers, so that the aerosol
particles converge in the lens axis by passing through lens orifices, which can produce a narrow
aerosol flow. In this work, injection efficiencies of the gas-jet transported materials into the ABS
nozzle were measured as a function of a flow rate of the carrier gas using fission products of 252Cf
and short-lived nuclides synthesized in nuclear reactions. The details of the experiments andresults will be discussed at the presentation.

1A16 Development of an ion-electron recombination atomic beam source for atomic beam
spectroscopy of superheavy elements
SUZUKI, H.1,2, ITO, Y.2, SATO, T1,2.,TOMITSUKA, T2,3., TOKOI, K1,2., TSUKADA, K2., ASAI,
M2., NAGAME, Y2.
(1Graduate school of science and engineering, Ibaraki Univ., 2ASRC JAEA, 3 Graduate school ofscience and technology, Niigata Univ.)
In the heavy element region, there is a possibility of violation of periodicity on electronic
structure of an atom by the influence of the relativistic effect. Especially, focusing on the groundstate electronic configuration of Lr (Z = 103), the valence electron orbital takes 7p1/2 rather than
6d3/2 assumed from the periodic rule. Our group has succeeded in measuring the first ionization
potential of Lr in recent years and obtained a strong support for the 7p1/2.
In this work, we have developed an ion-electron recombination atomic beam source for atomic
beam spectroscopy for direct determination of valence electron structures of superheavy element
atoms. An ion-electron recombination has an advantage of producing a low-energy atomic beam
without chemical dependences, while their recombination cross sections are so small. To
overcome the drawback, an electron focusing system “e-Neutra” has been implemented in theapparatus, where the ion beam focused and adjusted by an einzel lens and steerers is injected into
the center of a high-density electron cloud. As a result, a low-energy atomic beam is efficiently
produced by recombining with the electrons.
In the presentation, we will report on the experimental results and the details of the improved
ion-beam optics and the future prospects.

1B01 Relationship between radioactive cesium concentration and soil properties in depthsorted soil collected in Kawasaki, Japan
TAKAHASHI, T. 1, ICHIHASHI, M. 1, SAKANO, K. 2, KOIKE, Y. 2
(1Grad. Sch. of Sci. and Tech., Meiji Univ., 2Sch. of Sci. and Tech., Meiji Univ.)
Radioactive cesium was detected in soils sampled at Kawasaki, Japan.

Estimating thespeciation of radioactive cesium in soil is important for future migration studies. In this study,
radioactive cesium concentration and soil properties in depth-sorted soil were analyzed forpredicting the long term effect at observation site. The highest concentration of 137Cs wasobserved at a depth of 5 to 10 cm. In addition, the water content and the organic material content

showed an inverse correlation with 137Cs concentration. As a result of the sequential extraction
test, the chemical form of 137Cs was different from the surface layer of the soil and the soil deeper
than 10 cm in depth. 137Cs in the surface soil was present in an almost insoluble form. On theother hands, water soluble 137Cs was observed only in the soil at a depth of 10 to 20 cm. Fromthe sequential extraction method and soil property analysis, the activity distribution of 137Cs
showed different behavior at each depth of soil. The secondary transfer of radioactive cesium insoil over time was evaluated by combining depth profile analysis of 137Cs in soil with soil property
analysis.