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CHARACTERISTICS OF SPHERICAL
Cs-BEARING PARTICLES
COLLECTED DURING THE EARLY
STAGE OF FDNPP ACCIDENT
Yasuhito Igarashi, Kouji Adachi,
Mizuo Kajino & Yuji Zaizen
Atmospheric Environment and Applied Meteorology,
Meteorological Research Institute
1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan
Corresponding author: yigarash@mri-jma.go.jp
Talk outline
Research backgrounds, aims of the present study and
so forth
Radioactive aerosol sampling at the Meteorological
Research Institute (MRI), methodologies for analysis of
Cs-bearing particles with state-of-the-art instruments
including scanning electron microscope (SEM)
Characteristics of spherical Cs-bearing particles
including morphology, size and major components
Modeling approach with state-of-the-art aerosol
transport simulation considering the present spherical
Cs-bearing particles
Summary
Research Background: Temporal
change in atmospheric deposition of
radionuclides at MRI, Japan
10-1
101
103
105
107
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
137Cs
90Sr Koenji, Tokyo
Tsukuba
Rad
ioac
tiv
ity
de
po
sit
ion
(m
Bq
/m2/m
on
th)
Year
Nuclear tests by
former USSR, USA, etc.
Chernobyl Accident
Nuclear tests by China
Fukushima Accident
137Cs depo.: (23±0.9)×103 Bq/m2
in March 2011
90Sr depo.: 4.4±0.1 Bq/m2
in March 2011
Max. 137Cs depo.: 550 Bq/m2
in June 1963
Max. 90Sr depo.: 170 Bq/m2
in June, 1963
Nuclide Half life Emission/g
Xe-133 5.25d 1590
Te-129m 33.6d 3.0
Te-132 3.26d 7.8
I-131 8.04d 35
I-133 20.8h 1.0
Cs-134 2.06y 380
Cs-137 30.0y 4660
Sr-89 50.5d 1.9
Sr-90 29.12y 28
Pu-239 24100y 1.4
Pu-240 6540y 0.4
Fukushima radioactivity emission
inventory:Just a few kgs in weight!
Cf. Daily SO2 emission in Japan:2×109 g(EAGrid2000)
Conversion
Nuclear and Industrial
Safety Agency Estimate Emission in mass
Nuclide Half life Emission/PBq
Kr-85 10.72y
Xe-133 5.25d 11000
Te-129m 33.6d 3.3
Te-132 3.26d 88
I-131 8.04d 160
I-133 20.8d 42
Cs-134 2.06y 18
Cs-136 13.1d
Cs-137 30.0y 15
Sr-89 50.5d 2
Sr-90 29.12y 0.14
Pu-239 24,065y 0.0000032
Pu-240 6,537y 0.0000032
Investigation is needed regarding mixed states
with not only the radionuclide but also the
general atmospheric aerosol.
∴ Most of radionuclides occurred in the aerosol
form, which floated and transported in the
atmosphere.
From Petroff et al. (2008)
Deposition of aerosols in environ. and humans
Dry depo. onto forest
Kajino, Igarash & Fujitani,
Jpn. Soc. Atmos. Environ.,
2014 (in press) Hyg
ros
co
pic
ity
Deposition rate
Inhalation Particle size
Wet depo.:
CCN activity
Radioactive Aerosols
Aerosol size=physical
and
hygroscopicity=chemical
information
are very important!
Result of aircraft
monitoring made by
the Ministry of
Education, Culture,
Sports, Science and
Technology (MEXT) (Total of cumulative 134,137Cs pollution of the surface (kBq/m2) in the range that the survey completed up to fall, 2011) Nov. 11, 2011 Announcement
POLLUTION MAP
Tsukuba
Sampling, sample preparations and radionuclides measurements
HV filter sampling Total = Wet and dry
deposition sampling
Rotary evaporator Hydraulic press machine
4 m2 deposition sampler
Punched out 33 mmφ
Stocked samples
For Sr analysis
For γ-measurement
For γ-measurement
Until March 2011
8"×10“
Quartz
fiber filter
Radioactivity in aerosol samples at
MRI in March 2011
10-6
10-4
10-2
100
102
3/11 3/15 3/19 3/23 3/27 3/31
99Mo
132Te
131I
129Te
129mTe
133I
134Cs
137Cs
136Cs
Acti
vit
y c
on
ce
ntr
ati
on
(B
q/m
3)
Date
ND levels
In logarithmic scale
Igarashi et al., ICAS2011
#5 March/14-15 (700 m3) #6 March/15a (253 m3) #7 March/15b (233 m3)
#8 March/15-16 (498 m3) #14 March/20-21 (487 m3) #15 March/21-22 (1011 m3)
The BG image with homogeneous distribution vs Hot spots
with irregular distributions like Japanese sesame senbei.
= Strong radioactive particle was seen. However, the black spot in the image doesn't show the size of the particle directly.
Eve
nt 1
Event 2
Digital radiography with courtesy of Dr. Osada, Nagoya Univ.
HV filter samples collected at MRI
In April 2011
(more than a
month later
the accident)
images were
taken.
Imaging plate picture of HV filter sample
Exploit for strong radioactive particle
Pick up
Low vacuum-low acceleration
bias SEM・with EDS mapping
IP imager
Activity measurement with Ge detector
Providing
position data
SEM image of
quartz fiber filter
Extraction of the particle
Nano-XRF
Micro-manipulator
3 cm 1 cm 1 mm
2.6 µm
100 μm 2 μm
Exploit for strong radioactive
particle
Downsize
Particle1
Adachi et al., Sci. Rep., 2013; doi: 10.1038/srep02554
2.6 µm
Detected elements by EDS:
O, Na, Si, Cl, Fe, Mn, Zn, Cs
2.6 µm
SEM image of particle 1
Adachi et al., Sci. Rep., 2013; doi: 10.1038/srep02554
Cs-ball
d)
0 5 10 15
Inte
nsi
ty (a.u
.)
keV
Substrate (back g round)
Zn Pb
Fe
Si
Na
Pb
keV
Fe
Zn
Cs Cs
5 10
CaC
O
KS
Cs
Mn
Adachi et al., Sci. Rep., 2013; doi: 10.1038/srep02554
EDS
spectrum of
Particle 1
Elemental mapping by EDS analysis
Particle 1
Particle 1 137Cs: 3.27 ± 0.04Bq 134Cs: 3.31 ± 0.06 Bq
~6 Wt% within the particle
Particle 2 137Cs: 0.66 ± 0.02 Bq 134Cs: 0.78 ± 0.04 Bq
~3 Wt% within the particle
Measurement: 50,000 sec
Adachi et al., Sci. Rep., 2013; doi: 10.1038/srep02554
Gamma-spectrum of Cs-ball from
Mar.14-15 HV filter
Photo peaks with * are from the background or the glass substrate.
Collection of Cs-ball
1.7 µm
Fe, Zn, Cs
Particle 2
Particle 3
2.1 µm
O, Na, Cl, K, Fe, Mn, Zn, Cs
3.0 µm
Particle 4
O, Si,Cl, K, Fe, Zn, Rb, Sn, Cs
Particle 5
1.3 µm
C, O, Na, Cl, Fe, Zn, Rb, Sn, Cs Particle 6
from Tsukuba Univ.
2.2 µm
O, Cl, Fe, Zn, Rb, Sn, Cs
137Cs: 1.4±0.1 Bq, 0.13 TBq/g
3.3±0.2 Bq, 0.06 TBq/g
1.0±0.1 Bq, 0.2 TBq/g
1.4±0.1 Bq, 0.1 TBq/g
Specific
activity calc.
assume
density of 2
g/cm3
y = 1.0101x + 0.0435
R² = 0.996
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
13
4C
s/B
q
137Cs /Bq
Decay corrected as of
March 14, 2011
Cesium isotopic composition of Cs-
ball (In total 7 particles)
*One data was not yet subjected to SEM analysis.
Elements identified in Cs-ball by
SEM-EDS (In total 6 particles) P
art
icle
nu
mb
er
in w
hic
h
co
rres
po
nd
ing
ele
me
nt
was f
ou
nd
0
1
2
3
4
5
6
C O Si Na Cl K Mn Fe Zn Rb Sn Cs
10-2
10-1
100
101
102
103
0 5 10 15 20 25 30 35 40
Ba
-Kα
Cs-K
β1,3
Cs-K
β2
Tho
m. S
ca
t.
(37
.5 k
eV
)
Cs-K
α
Sn
-Kα
Sn
-Kβ
1,3
Sn
-Kβ
2
Sb
-Kα
Te
-Kα
Mo
-Kα
Mo
-Kβ
Rb
-Kα
Rb
-Kβ
Fe
-Kα
Zn
-Kα
Fe
-Kβ
Zn
-Kβ
Pb
-Lα
Pb
-Lβ
Cs-L
Zr-
Kα
- Particle - Background (carbon tape)
Results of synchrotron radiation-μ-XRF analyses N
orm
aliz
ed
in
ten
sity
(vs. T
ho
m. S
ca
t.)
Comparison of XRF spectra of the particle and background (37.5 keV-excited).
Energy /keV
Ba-Kα Cs-Kα Te-Kα Sb-Kα Sn-Kα Mo-Kα Zr-Kα
Zn-Kα
Rb-Kα
Pb-Lα Fe-Kα SEM image
2 μm
Results of μ-XRF imaging analysis
(37.5 keV-excited) and SEM image
of the particle.
Elements in particle: Ba, Cs, Te, Sb, Sn, Mo, Zr, Rb, Zn, Fe
(Pb : derived from an attached fragment of the filter)
Unpublished data: Courtesy of Prof. Nakai and Dr. Abe, Tokyo Univ. Sci.
Mar. 14-15 sample contained insoluble materials not only in water but hot nitric acid !
Characteristics of Mar.20 plume and particles seem to be different from those of 14-15.
Extraction efficiency of 137
Cs from HV
filter samples
Detected elements by EDS:
O, Si, Na, Ca, Mg, Fe, K, Al, Cl, Zn, Cs
SEM image of a remained particle on
HV filter after nitric acid extraction
1.1 µm
0.3±0.03 Bq
Similar type
of Cs-ball
was found! Mar. 15 sample
IP exposed for 24h.
Particle 7
MANAL-NHM-PM/r (Δx=4km)
ATK
ACM
DU
POL
RNW
CLD
ICE
SNW
GRW
Gas
Aerosols Hydrometeors
PRI
SS
Coalescence
IN activation
CCN activation
Dissolution
Cloud
microphysics
We
t d
ep
ositio
n (
Ra
in, S
no
w)
Co
ag
ula
tio
n
ATK (Aitken mode), PRI (primary radionuclides), ACM (accumulation
mode),DU (dust), SS (sea salt), POL (pollen)
Dry
de
po
sitio
n (Passive-tracers Model for radioactivity, off-line coupled with NHM)
Condensation/
Evaporation
Difference in simulated depo. due to
difference in aerosol characteristics
March 11 to 22, 2011
Total depo.(kBq m-2)
Dry depo. velocity becomes about 4 times. No
CCN activity. Removal by only rain drops
encounter (scavenging).
Cs depo. emitted on March 14 only (kBq m-2)
Submicron hygroscopic (CMD = 102 nm, κ=0.4) CMD= 2μm, κ=0
SUMMARY 1
We have found spherical Cs-bearing particles (Cs-ball) from HV filter samples collected during Mar. 14-15, 2011, when the first radioactive plume arrived from the FDNPP accident at the MRI as well as Univ. Tsukuba, Japan
So far seven Cs-balls were found from any given black dot on IP image of the filter sample.
They have basically spherical morphology, characterized composition of Fe, Zn, Mn, O, etc. with an appreciable amount of elemental Cs.
They are a few microns in diameter (corresponding to PM2.5) with a few Bq activity but as high specific activity as sub-terra Bq/g.
They are insoluble; even refractory to conc. nitric acid. Also, the extraction experiments showed that the Cs-ball occupied major part in the Mar. 14-15 Fukushima plume.
They would persist for a long time in the environment as well as in living organisms.
SUMMARY 2
While the investigation on radioactive aerosol during the second plume arrival gave no such Cs-ball.
Aerosol model simulation gave the results that non-hygroscopic super-micron Cs-ball could be removed more by the dry deposition and below-cloud scavenging than conventional sulfate-hosted particles.
A few Cs-balls have been subjected to the analysis of synchorotron X-ray analyses by using Spring-8 (Prof. Nakai and Dr. Abe, Tokyo Univ. Sci.).
The finding should be a key to understand the processes of the FDNPP accident, to accurately evaluate the health and environmental impacts and to improve efficiency of the decontamination of the polluted area.
Further studies are recommended for the present Cs-ball in more detail !
ACKNOWLEDGMENT
Y. Igarashi acknowledge the following people for their support and collaboration; Prof. I. Nakai, Dr. Y. Abe and Mr. Iizawa (Tokyo Univ. Sci.) for
their advanced analysis by using Spring-8.
Prof. Sueki and Mr. Sato (Univ. Tsukuba) for providing a filter sample
Dr. M. Mikami (MRI) for general support and Dr. M. Aoyama (MRI) for helping HV sampling
Mayama, Hida, Kimura, Sako, Inukai, Kamioka, Iwai, Kamiya, Yanagida, Nabeshima, and Takeda (Part-time & temporary staffs at MRI)
Prof. K. Osada (Nagoya University), Prof. Y. Oki and Dr. Osada (Kyoto Univ. Res. Reactor Inst.)
Prof. Y. Onda (Univ. Tsukuba), Prof. T. Nakajima (Tokyo Univ.), Prof. M. Ebihara (Tokyo Metro. Univ.), Prof. A. Shinohara (Osaka Univ.) and others
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