Journal of Nuclear and Radiochemical Sciences, Vol. 23, pp. 5-13, 2023

ArticlesPreliminary Analysis of Spherical Iron-rich Particles Extracted from Moto-Ujina Beach
Sand as a Possible Tracer for the Hiroshima Black Rain
Satoru Endoa,*, Tsuyoshi Kajimotoa, Kenichi Tanakab, Hiroki Higuchia, Satoshi Fukutanic,
Koichi Takamiyac, Makoto Maedad, Yasuhito Igarashica

Quantum Energy Applications, Graduate School of Advanced Science and Engineering, Hiroshima University,
1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japanb
Department of Physics, Kyoto Pharmaceutical University, 5 Misasaginakauchi-cho, Yamashina-ku, Kyoto 6078414, Japanc
Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2 Asashiro-Nishi, Kumatori-cho,Sennan-gun, Osaka 590-0494, Japand
Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1
Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
Received December 10, 2022; Accepted February 6, 2023; Published online February 15, 2023
Sand samples were collected from Moto-Ujina Beach, Hiroshima in order to analyze spherical iron-rich particles,
which may have been produced by the Hiroshima atomic bomb explosion. Spherical iron-rich particles (5.86 g)
were extracted from the beach sand by magnetic collection. The extracted particles were analyzed by scanningelectron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) and γ-ray spectroscopy using a Ge detector. The SEM-EDS analysis revealed that the spherical particles were composed mainly of Si and O, and contained Na, Mg, Al, P, K, Ca, Ti, V, and Fe. The Ge detector detected 662 keV γ-rays with a count rate of 2.6 × 10−4
cps and the radioactivity of 137Cs was calculated to be 1.3 ± 0.5 mBq g−1. Although we could not definitively conclude that the particles originated from the atomic bomb explosion, we could not rule out the possibility that someof these iron oxide particles were formed by vaporization and condensation of bomb material and dust that
agglomerated during the Hiroshima bomb explosion.

1. Introduction
In summer 2021, policy decisions were made to provide
relief to victims thought to be affected by the “black rain”
caused by the atomic bomb explosion. However, even thoughmore than three quarters of a century has passed since theatomic bombs were detonated, little is understood about thefundamental and material sciences of the black rain. In thisstudy, we search for traces of the black rain by using new
methods developed for research into the Fukushima Daiichi
Nuclear Power Plant (FDNPP) accident. Despite numerous
attempts, including the 1976 and 1979 Ministry of Health andWelfare-led studies, black rain regions have never been identified by measuring only the radionuclides that remain in thesoil (e.g., Hiroshima City 2011, 2013)1,2. This is because theradionuclide signature from the atomic bomb explosion wasdrowned out by the superposition of radionuclides from theglobal fallout caused by atmospheric nuclear experiments in
the 1960s and 1970s. Therefore, we need to find new tracers
for the black rain.
Wannier et al.3 reported that unique types of melt debris ofhigh-temperature origin (>1800 °C) are contained in the sandat Moto-Ujina Beach, Hiroshima, Japan. They isolated agroup of particles consisting of spherical silica and iron oxide
particles, deformed candy-like glass particles containing air
bubbles, and many particles that also contained air bubbles
and that were melted and glazed after they were crushed.
These particles are coarse (hundreds of micrometers in size)
and abundant about ten thousand particles in total). Wannier
et al. 3 estimated the abundance of the particles to be about*Corresponding author. E-mail: endos@hiroshima-u.ac.jp

3000 tons around the coast of Hiroshima, and thus they concluded that on balance, the evidence suggested that the originof the particles was linked to the nuclear explosion of August
6th, 1945. Similar spherical particles were also identified following the FDNPP accident4−8 in 2011, although the size range
was far smaller. Therefore, we could take a similar approach
to identifying black rain particles as was applied to the
Fukushima particles. Accordingly, we have added the collection and analysis of spherical particle samples from the MotoUjina Beach to the objectives of our reinvestigation of theblack rain.
In this paper, we report an overview of sand sampling from
Moto-Ujina Beach and the method of spherical particle extraction, and we present the results of the scanning electron
microscopy-energy dispersive X-ray spectrometry (SEM-EDS)
analysis and γ-ray spectrometric measurements with a Ge
detector for the extracted particles.
2. Materials and methods
2.1 Sampling. The sampling was conducted on April 26
and August 26, 2021. Five lots of sand samples were collected
at each of the sampling locations (Uj01 to Uj05) on MotoUjina Beach, Hiroshima City, at intervals of several meters(Fig. 1). The sand samples were separately collected at depthsof 0–5 cm and 5–10 cm from the surface using a garden
shovel. The amounts of each sand sample are listed in Table 1.
As explained below, particles originating from the atomic
bomb are expected to be ion-rich because the major constituent of the atomic bomb dropped over Hiroshima was made ofsteel. In particular, the molten particles are believed to be© 2023 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 02/15/2023

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J. Nucl. Radiochem. Sci., Vol. 23, 2023

Moto-Ujina

Control
CNT01

Uj05
CNT05

Uj04

CNT02 CNT03 CNT04
Uj02

Uj03
Uj01

Figure 1. Sampling locations shown with an electronic map using GSI XYZ tiles (GSI 2021).

TABLE 1: GPS addresses of sampling locations.
Sampling location

Location

Longitude

Latitude

Number of points

Uj01
Uj02
Uj03
Uj04
Uj05
CNT01
CNT02
CNT03
CNT04
CNT05

Moto-Ujina Beach
Moto-Ujina Beach
Moto-Ujina Beach
Moto-Ujina Beach
Moto-Ujina Beach
Matoba Beach, Takehara
Matoba Beach, Takehara
Tadanomi-Nagahama, Takehara
Saizaki-Kuwaki, Mihara
Sunami Seaside Park, Mihara

132.4621
132.4645
132.4609
132.4583
132.458132.9214132.9226
132.967
133.0689
133.0823

34.340734.3416834.34186
34.34517
34.34605
34.32575
34.32567
34.33592
34.34342
34.35358

5
5
5
5
5
1
1
1
1
1

iron-rich because the steel base material is thought to havemelted and agglomerated in the fireball of the atomic bomb.
During sampling, iron-rich materials (about 61 g) were collected from the sandy beach at Uj01 using a magnetic toolbar(GISUKE) measuring 1.5 × 20 cm.
Sand samples were also collected as control samples onJune 1, 2021 from in Takehara and Mihara, 40–50 km from

Moto-Ujina Beach, which have sandy beaches similar toMoto-Ujina Beach. The five sampling locations at Moto-Ujina
Beach as well as the locations of the control samples areshown in Fig. 1 on the electronic topographic map (tile),
Geospatial Information Authority of Japan (GSI) 9, and thedetails are also listed in Table 1.

J. Nucl. Radiochem. Sci., Vol. 23, 2023

Preliminary Analysis of Spherical Iron-rich Particles Extracted from

7

Figure 2. Photograph showing an example of the extracted particles from a Moto-Ujina Beach sand sample.

CL-L

YL-M

CL-S

RD-S

BL-L

BL-S

250 µm200 µm300 µm300 µm500 µmYL-S

500 µm200 µmBL-Tw

500 µmFigure 3. Photograph of spherical particles used for SEM-EDS analysis.

2.2 Sample preparation. To remove sea salt from the sand,the sand samples were immersed in tap water that was threetimes the volume of the sand sample and left to stand for several minutes, and then the water was discarded. This process
was repeated five times. Then, a small amount of ethanol wasadded to the washed and water removed samples, which weredried under a stream of warm air for several hours. Afterwashing, the samples were sieved with a 1 mm mesh toremove large sand grains and shells.
2.3 Extraction of spherical particles. If the particles originated from the atomic bomb explosion, they would containiron from the vaporized bomb material, and thus a magnet wasused to extract the particles. The top of the thinly spread sandwas scanned with a magnet tool, and the grains sticking to themagnet were extracted. Spherical particles were picked out
from the extracted grains. A photograph of the extracted particles from sample Uj05-02U is shown in Fig. 2. The particle
size of the dispensing extracted particles (0.14 g, 4805 particles) was measured with a digital microscope (HRX-01, Hirox
Co., Ltd.).
2.4 SEM-EDS measurements. From the extracted spherical particles, four types of particles of different colors andsizes (transparent: CL; yellowish transparent: YL; black: BL;
red: RD, small: S; medium: M; large: L; twin: Tw) wereselected for SEM-EDS analyses with a scanning electron
microscope (S-5200, Hitachi High-Technologies Corp.) and an
X-ray spectrometer (Genesis XM2, EDAX). Photographs ofthe spherical particles used for SEM-EDS analyses are shownin Fig. 3.
2.5 Ge measurement. A total of 5.86 g of spherical particles comprising 3.69 g extracted from the 50 sand samples and2.17 g extracted from the 61 g of iron-rich materials collectedusing the magnetic tool bar was wrapped in pharmaceuticalwrapping paper and vacuum-packed with a food vacuum sealing system (Shinku-Pakken, Kurashi-no-Koubin) into a flat
plate of 3 × 4 cm for γ-ray spectroscopy with a Ge semiconductor detector (GMX-30200-P, Ortec). The Ge measurement
were carried out for 700,000 s on day 8 after packing. The
measurement efficiency of the Ge detector was determinedusing a planar standard source (MX421, Japan Isotope
Association), which is a 50-mm-diameter planar radiation
source consisting of nine radionuclides (51Cr, 54Mn, 57Co, 60Co,
85
Sr, 88Y, 109Cd, 137Cs, and 139Ce) encapsulated in a 4-mm-thickacrylic disk with a diameter of 60 mm. The PHITS code6 wasused for the Monte Carlo calculations, where the geometry of
the Ge detector was input and the measurement efficiency wascalculated by scoring the energy imparted by electrons to theGe crystal region for 22 monoenergetic γ-rays of 10 keV to
3 MeV.
3. Results and discussion
3.1 Extraction of spherical particles. For samples Uj01-01
to Uj01-02, a magnetic sample of about 0.5 g was obtained
from sand samples of 150–250 g with a grain size of less than
1 mm, and about 0.15 g of spherical particles were extracted
from each sample. The recovery rates of the samples are sum-

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J. Nucl. Radiochem. Sci., Vol. 23, 2023

marized in Table 2. Spherical particles were recovered at a
rate of about 10 −5 to 10 −3 for sand with a particle diameter of 1
mm or less around Moto-Ujina Beach. In the control samples
taken from the similar sand beach around Takehara and
Mihara regions, 1 or 2 spherical particles were observed atsampling locations CNT02 to CNT04. The particle size distribution for sample Uj05-02U (0.141 g) is shown in Fig. 4. The
mean diameter was 249 µm with one standard deviation of
70 µm. Assuming a particle diameter of 249 μm and a densityof 2 g/cm3, the ratio of spherical particles to sand with a particle diameter of 1 mm or less was estimated to be about 10 −8 to10 −7, which is 1–3 orders of magnitude lower than that aroundMoto-Ujina Beach.
3.2 SEM-EDS measurements. The SEM images in Fig. 5of the CL-L, CL-S, YL-M, YL-S, and BL-S particles showthat they were nearly spherical and had crater-like depressions
on their surfaces, similar to the radioactive particles foundduring the FDNPP accident investigation. The crater-like
depressions are thought to be caused by the bursting of gas
bubbles during agglomeration. In addition, the RD-S, BL-L,
and BL-Tw particles had a slightly distorted spherical shape,
which may be due to the adhesion of other substances to thesurface during the condensation processes.
Figure 6 shows the EDS spectra of the CL-S, YL-S, RD-S,
and BL-L bulk, and the RD-S and BL-L surfaces. The elements C, O, F, Na, Mg, Al, Si, P, K, Ca, Ti, V, and Fe wereidentified. Most of the C signal was from the C tape on which
the sample was placed. Therefore, it is intuitive to assume thatthese particles were formed by the vaporization and agglomeration of soil. The surface elemental analysis of the distorted
RD-S and BL-L samples showed an increase in Fe on the surface, unlike the bulk samples.
There are several possible origins for such particles, including natural sources such as impact spherules, meteorite ablation spheres, and small-scale volcanic dust, as well as
anthropogenic sources such as particulates from fireworks,
steam locomotives, and the use of power tools such as gas
fusion torches and angle cutters. Even the production or use ofmineral fibers could be the source. However, all of these particles can have similar morphologies. Micrometeorite-derived
particles are indicated in many cases by the presence of
Ni-bear ing iron metal or Mg-r ich Ni containing Fe10 .
Genareau et al. reported that volcanic spherules contain Si
with lower amounts of Al, K, Ca, and Fe11. There is a wide
range of anthropogenic particulates having various origins, but

TABLE 2: Sand samples with a grain size of 1 mm or less, magnet extraction volume, and particle extraction volume.
Sample name

Sand mass (g)Magnetically extracted sample (g)Extracted particles (g)Particles/sandUj01-01U
Uj01-01D
Uj01-02U
Uj01-02D
Uj02-01U
Uj02-01D
Uj02-02U
Uj02-02D
Uj03-01U
Uj03-01D
Uj03-02U
Uj03-02D
Uj04-01U
Uj04-01D
Uj04-02U
Uj04-02D
Uj05-01U
Uj05-01D
Uj05-02U
Uj05-02D

150.1
159.8
175.1
212.6
110.0
138.8
156.5
196.5
164.7
119.8
100.3
83.4
98.2
76.2
234.18130.84
121.3
55.4
62.7
77.6

0.98
1.04
1.27
1.33
0.20
0.22
0.26
0.33
0.11
0.07
0.13
0.086
0.23
0.25
0.56
0.26
0.16
0.11
0.14
0.20

0.15
0.13
0.15
0.206
0.012
0.013
0.01
0.02
0.01
0.01
0.007
0.002
0.01
0.01
0.01
0.01
0.01
0.01
0.01960.00949.99 × 10−4
8.14 × 10−4
8.57 × 10−4
9.69 × 10−4
1.09 × 10−4
9.37 × 10−5
6.39 × 10−5
1.02 × 10−4
6.07 × 10−5
8.35 × 10−5
6.98 × 10−5
2.40 × 10−5
1.01 × 10−4
1.31 × 10−4
4.26 × 10−5
7.64 × 10−5
8.24 × 10−5
1.81 × 10−4
3.12 × 10−4
1.21 × 10−4

CNT01U
77.4
0.15
0
0
CNT01D
186
0.45
0
0
−5
CNT02U
221
0.56
1.62 × 10 (1)*7.32 × 10−8
−5CNT02D
231.5
0.71
3.23 × 10 (2)*1.40 × 10−7
CNT03U
235.8
0.13
1.62 × 10−5 (1)*
6.86 × 10−8
−5CNT03D
273.5
0.13
1.62 × 10 (1)*
5.91 × 10−8−5CNT04U
225.4
0.57
3.23 × 10 (2)*1.43 × 10−7
CNT04D
280.8
0.62
1.62 × 10−5 (1)*5.76 × 10−8
CNT05U
84.6
0.06
0
0
CNT05D
155.3
0.13
0
0
*: Weight of one particle assuming a mean diameter of 249 μm and a density of 2 g/cm3. The numbers in parentheses are the numbers of confirmed spherical particles.

J. Nucl. Radiochem. Sci., Vol. 23, 2023

Preliminary Analysis of Spherical Iron-rich Particles Extracted from

9400

Frequency

300

200

100

0
0

100

200

300

400

500

600

700

800

900

1000

Particle radius (µm)
Figure 4. Particle size distribution for sample Uj05-02U.

CL-L

CL-S

100 µm300 µmRD-S

100 µm200 µm200 µm
BL-S

BL-L

200 µm

YL-S

YL-M

BL-Tｗ

500 µm500 µmFigure 5. SEM images of CL-L, CL-S, YL-M, YL-S, RD-S, BL-L, BL-S, and BL-Tw particles.

iron oxide is often given off during the use of power tools, andparticles from different colors of fireworks tend to containmetal salts of Sr/Li (red), Ca (orange), Na (yellow), Ba (green),and Al/Ti/Mg (silver/white)12.
The EDS spectra suggested that all CL-S, YL-S, RD-S, and
BL-L particles contain Al, Ca, and Fe, and to a lesser extent
Mg and Ni, suggesting a low possibility of a micrometeoritederived origin. The other 12 elements were similar to the elemental components in the soil or the radioactive hot particles
from the FDNPP accident 5. Therefore, it is intuitive toassume that these particles were formed by the vaporization
and agglomeration of soil or rocks. In the Chugoku region,
Mt. Sanbe is estimated to have been volcanically active at least
three times between 3600 and 4500 years ago13. The Abu volcano group is in neighboring Yamaguchi Prefecture, and themost recent eruption is estimated to be 8800 years ago 14. The
volcanic ejecta from these volcanic activities is mainly dacite
but also includes fallen volcanic ash, pyroclastic flows, lava
eruptions, formation of pyroclastic hills, and generation of volcanic mudflows. In particular, pyroclastic flows and volcanic
mudflows can reach distant areas. If the spherical iron-richparticles observed were of volcanic origin, we would expect tofind the same amount of spherical iron-rich particles in thesamples from the Takehara-Mihara area, which we used as acontrol. We found far fewer spherical particles in the control
samples, suggesting that the spherical particles were not volcanic and could have originated from the atomic bomb explosion. Nevertheless, we could not exclude micrometeorites ordomestic and industrial activities such as shipbuilding, automobile fabrication, and garbage incineration as sources for the
spherical particles. It should also be noted that fireworks festivals have been held for many years on Miyajima, an island
near Hiroshima that is one of the most popular tourist destinations in Japan.
3.3 Ge measurement. The results of Ge measurement of
5.86 g of spherical iron-rich particles and the background areshown in Fig. 7 as count rate spectra. The signals from theradionuclides were small and about twice as large as the background. In addition, 210Pb, 214Pb, 214Bi, and 224Th from the uranium series and 208Tl, 212Pb, 212Bi, and 228Ac from the thorium
series were identified. Furthermore, although not statisticallyEndo

J. Nucl. Radiochem. Sci., Vol. 23, 2023
700(a) CL-S bulk

Si

600

Counts

500
400

Al

C O

300

Ca

200

Mg

100
0
1200

K

O

TI

Fe

V

Si

1000

(b) YL-S bulk

Al

Counts

800
600

C

400

Mg
Fe Na

200
0

0

K

1

2

Ca

TI

3

Fe

V

4

5

6

7

8

9

10

X-ray energy (keV)

3000(c) RD-S bulk

O
2500

Si

Counts

2000

Al

1500
1000

C

Fe Mg
Na

500

K

TI

Ca

Fe

V

0
2500

(d) RD-S surface

O

Counts

2000

1500

1000

Al

C

Mg

500

0

Fe
0

Fe

Si
K

Na
1

2

TI

Ca

3

4

V
5

6

7

8

9

10

X-ray energy (keV)

1800

Si

1600

(e) BL‐L bulk

1400

O

Counts

1200
1000
800

Al

600

Mg
FeNa

C

400
200

K

Ca
TI

Fe

V

0
600

(f) BL‐L surface

Fe

500
400
Counts

10

O
300
200

C

100
0

Fe

Si P
NaMgAl

0

1

2

K
3

TI

Ca
4

V
5

6

7

8

9

10

X‐ray energy (keV)

Figure 6. EDS spectra of the (a) CL-S bulk, (b) YL-S bulk, (c) RD-S bulk, (d) RD-S surface,(e) BL-L bulk, and (f) BL-L surface.

J. Nucl. Radiochem. Sci., Vol. 23, 2023

Preliminary Analysis of Spherical Iron-rich Particles Extracted from

0.03

Counts per sec

Particles 5.86g g
BG

(a)

0.025

63 keV 224Th

0.02

186 keV 235U+226Ra

46 keV 210Pb

0.015

144 keV 235U

0.01
0.005
0

0

50

100
Gamma energy (keV)

150

200

0.02
0.018
0.016
Counts per sec

238 keV 212Pb(b)

352 keV 214Bi

0.014

295 keV 214Pb

0.012
0.01

338 keV 228Ac

0.008
0.006
0.004
0.002
0

200

250

300
Gamma energy (keV)

350

400

0.008

609 keV 214Bi

0.007

(c)

662 keV 137Cs

Counts per sec

0.006
0.005

662 keV 137Cs

0.004

727 keV 212Bi

0.003
650

0.002

660

670

0.001
0

600

650

0.003

911 keV 228Ac

0.0025Counts per sec

700
Gamma energy (keV)

0.002

750

800

(d)

968 keV 228Ac

1001 keV 234mPa

860 keV 208Tl

0.00150.001
0.0005
0

850

870

890

910

930
950
970
Gamma energy (keV)

990

1010

1030

1050

Figure 7. γ-ray spectra of the spherical particles measured with a Ge detector. (a) 0–200 keV
region, (b) 200–400 keV region, (c) 600–800 keV region, and (d) 850–1050 keV region.

11

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TABLE 3: Radioactivity in the 5.86 g sample of sphericalparticles and sand.
Nuclide
Pb
Th
226
Ra
214
Pb
214
Bi
234m
Pa
212
Pb
228
Ac
208
Tl
235
U
137
Cs
40
K
210

234

U series

Th series

Radioactivity
in 5.86 g sample(mBq/g)
86.9
91.6
147.2
94.1
107.3
119.8
85.4
79.9
58.5
4.7
1.3
107.3

± 7.1
± 7.9
± 11.4± 1.7± 6.0± 75.1
± 1.3
± 4.4
± 5.4
± 2.5
± 0.5
± 6.0

Radioactivity
in sand (mBq/g)
8.7
7.7
23.2
9.7
8.2
ND
8.2
13.0
4.7
ND
0.5
8.2

± 6.8
± 7.3
± 10.5
± 1.5
± 5.3
± ND
± 1.0
± 4.1
± 1.5
± ND
± 0.6
± 5.3

TABLE 4: U, Th, and K concentrations in the sphericalparticles, reference rock JG-3 from the Chugoku region(Imai et al. 1995), and soil from the Ohta River in
Hiroshima City (AIST 2022)
U concentration
Th concentration
K concentration

Particles

JG-3

Ohta River

8.67 ppm
20.6 ppm
0.35%

2.21 ppm
8.28 ppm
2.19%

4.23 ppm
15.68 ppm
2.04%

beach sand were generated by the Hiroshima atomic bomb
explosion in August 1945, although origins from other sources
do not appear to be realistic, as discussed by Wannier et al.3 In
future work, we will confirm the abundance of uranium isotopes in the particles from the Moto-Ujina beach by usingmass spectroscopic measurements, such as ICP-MS and secondary ion mass spectrometry to draw a more definitive conclusion about the origins of the particles.
Acknowledgements

significant, the 1001 keV γ-rays from
Pa and the 144 keV
γ-rays from 235 U were slightly higher than the background.
Also, a small amount of 662 keV 137Cs γ-rays were detected.
The radioactivity concentrations converted from these countrates are shown in Table 3. A sand sample of 5.86 g was alsomeasured with the Ge detector. The signs in Table 3 show thatthe count rates for the 5.86 g spherical iron-rich particle sample were twice or more those of the 5.86 g sand sample; thus,
the concentrations of the uranium and thorium series radionuclides in the spherical particle sample were different fromthose in the sand sample. The U, Th, and K concentrations in
the particles were estimated to be 8.67 ppm, 20.06 ppm, and
0.35%, respectively. The U, Th, and K concentrations of theparticles were slightly higher than those of the reference rockJG-3 for the Chugoku region15 and those of the soil from Ohta
River in Hiroshima City16 (Table 4). This result suggests thatthe soil in Hiroshima may have provided the raw materials forthe spherical iron-rich particles.
These results identified radon precursors in the uranium
and thorium series, suggesting that 234m Pa and 235 U may bepresent in very small amounts in the spherical iron-rich particles. However, no clear evidence of a U isotopic signature wasobserved. The ratio of 235U/238U = 0.006727 ± 0.00503, which
was calculated from 235U and the averaged value of 238U daughter concentrations, was similar to the natural abundance of
0.00726. To confirm the atomic bomb explosion origin of thespherical iron-rich particles, mass spectroscopy measurements, including inductively coupled plasma-mass spectroscopy (ICP-MS), should be performed.
234m

4. Conclusions
Sand samples were collected from the beach on Moto-Ujina
Island in order to analyze spherical iron-rich particles, which
may have been produced by the Hiroshima atomic bomb
explosion. About 6 g of spherical particles were extracted
from the sand samples collected from Moto-Ujina Beach. The
extracted samples were analyzed by SEM-EDS and by γ-ray
measurements with a Ge detector. SEM-EDS analysis revealed
that the particles were composed mainly of Si and O and also
contained Na, Mg, Al, Si, P, K, Ca, Ti, V, and Fe. The Ge
detector measurements detected 137Cs (1.3 ± 0.5 mBq g −1),radon progenies from the uranium series and thorium series,and small amounts of 234mPa and 235U in spherical iron-rich particles. However, we still could not definitively conclude thatthe spherical iron-rich particles isolated from the Moto-Ujina

The SEM-EDS measurements were performed in the
Natural Science Center for Basic Research and Development(N-BARD), Hiroshima University. The authors are grateful tothe staff N-BARD. This study was carried out as a part of the“Study on the Construction of a Meteorological Simulation
Model for the Atomic Bombings and the Analysis of Fallout
Dispersion,” funded by the Ministry of Health, Labour andWelfare of Japan.
References[1]	Hiroshima City, Revisit the Hiroshima A-bomb with a
database, Edt. Aoyama M and Oochi Y, 978-4-99059350-6, 2011.
[2]	Hiroshima City, Revisit the Hiroshima A-bomb with a
database Vol. 2, Edt. Aoyama M and Oochi Y, 978-49905935-1-3, 2013.
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