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