Development and application of radiochemical methods based on the use of ICP-MS instruments

Jian Zheng

National Institute of Radiological Sciences Institute of Quantum and Radiological Science and Technology (QST)

99Tc 239 234U Pu 240 235U Pu 241 238U Pu

135 230Th Cs 137 232Th Cs 241 Am 1

Hospital Dept. of Charged Particle Therapy Research Dept. of Molecular Imaging and Theranostics Dept. of Functional Brain Imaging Research Dept. of Accelerator and Medical Physics Dept. of Radiopharmaceuticals Development Dept. of Radiation Measurement and Dose Assessment Dept. of Radiation Effects Research Dept. of Basic Medical Sciences for Radiation Damages Fukushima Project Headquater Human Resources Development Center Radiation Emergency Medicine Center

ICP-MS Radionuclides analysis

Tokyo

National Institute of Radiological Sciences Institute of Quantum and Radiological Science and Technology (QST) Japan Contents ■Development of advanced mass spectrometric techniques for radionuclide (actinides, Cs) analysis • Sensitivity improvement • Chemical separation development

■Pu isotopes as geochemical tracer: transport process in the ocean

■Tracing Fukushima nuclear accident released Pu and Cs isotopes in the environment

3 Development of advanced mass spectrometric techniques for radionuclide analysis

USN

ETV

HG

LA

DIHEN

First review: sensitivity comparison between ICP-MS and radiometric techniques

Detection limit 0.16 – 0.38 pg/mL For 99Tc, 232Th, 237Np, 238U, 239Pu （long half-life) Development of advanced mass spectrometric techniques for radionuclide analysis

Rapid development of ICP-MS analysis of radionuclides at NIRS: Pu, Am isotopes 1990s 2004 2006 2015

SF-ICP-MS ICP-QMS SF-ICP-MS Jet-interface ICP-QMS shield torch desolvation desolvation 10-13 g

10-14 g

10-16 g High efficiency sample introduction: APEX or Aridus II SF-ICP-MS, Element 2 XR

APEX-Q high efficiency Electrostatic sample introduction system analyser Attogram SEM

Heated cyclonic Exit slit levels spray chamber (100-140 0C) -18 Ar X-skimmer cone 10 g nebuliser gas Entrance Ar sweep gas in slit

Heated fluoropolymer ICP Magnetic membrane analyser Zheng & Yamada, Talanta, 2006 Ion optics Ar sweep gas out Condenser (2/-50C) Zheng & Yamada, J. Oceanogr. 2008 Pumped drain Zheng, JNRS, 2015 Development of advanced massPu spectrometric、Am同位体：分析法 techniquesの検討及び環境中の挙動について for radionuclide analysis

Major interferences for ultra-trace Pu-Am analysis using ICP-MS

Analyte Interferences for ICP-MS analysis

239 238 1 + 207 16 + 204 35 + 199 40 + Pu U H , Pb O2 , Pb Cl , Hg Ar

240 238 1 + 208 16 + 200 40 + Pu U H2 , Pb O2 , Hg Ar ,

241Pu 241Am+, 206Pb35Cl+, 204Pb37Cl+, 209Bi16O +, 209Bi32S+, 2 241 241 + 206 35 + 204 37 + 209 16 + 209 32 + Am Pu , Pb Cl , Pb Cl , Bi O2 , Bi S , 201Hg40Ar+, 205Tl36Ar+

243Am 208Pb35Cl+, 207Pb36Ar+, 206Pb37Cl+, 209Bi34S+, 203Tl40Ar+

Using higher resolution (MR mode) can resolve most of the interferences, but result in decrease of sensitivity. Resolution between UH+ and 239Pu can not be achieved with the highest resolution offered by SF-ICP-MS.

Chemical separation is essential for accurate determination. 6 Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis

U concentration is 106-109 times higher than Pu in solid environmental samples such as soil, sediment

U in seawater: ca. 3 mg/m3 Pu in seawater: ca. 0.2 pg/m3

U = 1010 Pu !!

Mass Polyatomic interference from 238UH+ and peak tailing of 238U

Elimination of UH+ polyatomic interference

Zheng & Yamada, Talanta, 2006 7 Isobaric/polyatomic interferences in ICP-MS analysis of 241Am

Isobaric/Polyatomic Total mass Resolution required interferences of 241Am (m/Δm) Pu 241Pu 241.05685 11,400,000 240Pu1H 241.06163 50122 Bi 209Bi32S 240.95246 2310 209 16 Bi O2 240.97022 2784 206Pb35Cl Pb 240.94331 2124 204Pb37Cl 240.93894 2045 205Tl36Ar 240.94197 2099 Tl 207Pb34S 240.94376 2132 201Hg40Ar 240.93268 1942 Hg 179 14 16 Hf N O3 240.93363 1957 178 14 16 1 Hf N O3 H 240.93934 2052 Hf 195 14 16 Pt N O2 240.95769 2432 194 14 16 1 Pt Pt N O2 H 240.96340 2580 204Hg37Cl 240.93939 2053 208Pb16O 1H 240.97430 2921 Remove 2 If medium resolution mode (m/Δm=4000) is used, most of interferences can be solved. Decrease of sensitivity (241Am, 432 y, lower sensitivity compared to Pu) large sample size for ultra-trace analysis Matrix effect in ICP-MS measurement

Matrix effect (IUPAC definition) The combined effect of all components Sensitivity of the sample other than analyte on the increase measurement quantity Sensitivity decrease

Concentration ranges of trace and ultra-trace elements in soils of Japan. Data from Yamasaki et al. 2001 Determination of radionuclides in environmental samples by ICP-MS River water Seawater Concentration/separation Liquid Sample Sediment Samples Solution Soils etc Ash  Digestion Heat block digestion Solid Microwave digestion Sample

Sample Extraction Solution Liquid Co-precipitation Chromatographic introduction separation Matrix removal ICP-MS

High Pretreated Matrix Solid phase extraction Liquid Liquid Co-precipitation Sample Sample High efficiency sample introduction Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis

Ashing temperature effect on Pu analysis in soil samples plagioclase-like

High temperature ashing resulted in Pu loss Wang, Yang, Zhneg* et al. Anal Chem 2015 11 Matrix effect in ICP-MS measurement Co-precipitation: matrix removal

Matrix remained in liquid phase separated from Pu-Am

Co-precipitated percentage of soil matrix by Fe(OH)3, CaC2O4 and CaF2 co-precipitations (n=3) Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis Pu separation based on extraction chromatography TEVA-UTEVA-DGA 10 M HNO3-1 M HF

CaF2/LaF3 co-precipitation Matrix removal

Connect UTEVA-DGA after (3) Load Pu(III) on DGA !

Analytical procedure for soil, sediments

Wang, Zheng* et al., Anal Chem. 2017 Separation of interfering elements 13 Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis Pu separation based on extraction chromatography Soil/Sediment samples

14 Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis Pu separation based on extraction chromatography For small volume seawater samples (10-20 L)

Seawater Pu(V) or Pu(VI)

Pu(III) favorable under-go co-precipitation

High Pu concentration efficiency

of Fe(OH)2 (ca. 100%), Pu-242 can be added after the

Fe(OH)2 co-precipitation.

Making it possible: on-boat Co-precipitation without adding Pu-242 15 Development of advanced先端同位体質量分析法の開発 mass spectrometric techniques for radionuclide analysis

Extremely high U DF: interference free Pu measurement

10000 Operational blank a

1000

100

10

1

238 239 240 241 242 20 L seawater 10000 b

1000

100

10

1 238 239 240 241 242 Atom mass Mass spectrum of 20 L seawater Mass spectrums for sediment (30g)

+ U decontamination factors: UH+/U ratio for our Contribution of UH to Sediment method: 2×106 239 system:1~3×10-5 Pu intensity: < 1 cps Seawater method: 1×108 Desolvation system No math correction!

16 Separation chemistry for 241Am analysis by SF-ICP-MS

The behaviors of interfering elements on DGA-N resin

HNO3 HNO3

HCl HCl

Separation Am from REEs in DGA-N and TEVA resins

DGA-N

TEVA

For large size soil samples, REEs cause matrix effect for ICP-MS! ICP-MS for ultra-trace measurement of 241Am

No REEs separation

Wang, Zheng*, Tagami et al. Anal Chem 2016 ICP-MS measurement of 241Am: method validation

241 NIST 4357 IAEA-375 Am analysis in six reference materials IAEA-384 IAEA-soil-6 IAEA-385 NIST-4354

■The agreement between measured 241Am activities and certified values validated the accuracy of developed method.

■The chemical recovery of Am is steady for soil and sediment samples (76% to 82%).

■The low LOD (0.012 mBq/g or 0.024 fg/mL) makes this method suitable for analysis of ultra-trace level Am in large soil samples (2-20g). Sources of radiocesium isotopes in the environment

■ High yield fission products 6.535% for 135Cs and 6.236% for 137Cs from thermal neutron fission of 235U.

■ A shielding of 135Cs occurs due to neutron capture of its precursor, 135Xe, to form 136Xe, whereas production of 137Cs is unaffected. This process causes a high degree of variance of 135Cs/137Cs isotope ratio with source.

Chernobyl accident: 0.28-0.32 Global fallout source: ca. 2.0-2.7 Fukushima accident: 0.34 (2011/3/11)

Fukushima accident Challenge for 135Cs and 137Cs analysis ■Due to the long half life (2.3x106 y) and low-energy β-decay (205 keV), the radiometric counting method is impractical for environmental samples ■Only TIMS and ICP-MS with reaction cell realized 135Cs and 137Cs analysis in environmental samples. TIMS: Lee et al., GCA, 1993; Snow et al. IJMS, 2015; Snyder et al., JER, 2012; Shibahara et al., JNST, 2014 ICP-MS: Taylor et al., JER, 2008, ICP-QMS; Russell et al., AC, 2014, SF-ICP-MS; Zheng et al., AC, 2014, ICP-MS/MS; Ohno et al., JAAS, 2014, ICP-MS/MS

ICP-MS/MS

Russell et al., AC, 2014, SF-ICP-MS Chemical separation for environmental samples

AMP Cs selective adsorption AG MP-1 M Anion-exchange resin Separation Mo, Sb, Sn

1-40g AG 50W-x8 Cation-exchange resin & Sr resin Separation major matrix and Ba

Ba, Mo < 5 ppb Sn, Sb < 0.5 ppb Cs recovery: 95 % Matrix elements separation

AG 50W-X8 Cation-exchange column Method 1: Muromac M , 1.5 M HCl

Method 2: Muromac M, 1 M HNO3 with Sr resin Method 3: Eppendorf column, 1 M HNO3 with Sr resin

Zheng et al., Anal Chem., 2016b 135Cs and 137Cs analysis using ICP-MS/MS Chemical resolution Finally, Q2 is set to measure the desired 135Cs and 137Cs

Target ions are separated from matrix ions by Q1 set at m/z 135 and 137, BaO+, BaOH+ respectively, and they enter the collision/reaction cell where

• they react with N2O to separate Cs/Ba, • eliminate MoAr+ polyatomic interference, • suppress formation of BaO+, BaOH+ SbO+ and SnO+.

Zheng et al., Anal Chem., 2014 Chemical resolution of Cs from interfering Ba in ICP-MS/MS APEX desolvation system for sensitivity increase

ion-molecule reaction + ⇒ + + Micromist nebulizer Ba + N2O BaO , BaOH 0.4 mL/min Cs (1 ppb)-Ba (5 ppb) Cs+ remains unreactive

APEX-ICP-MS/MS, Micromist nebulizer 0.4 mL/min, Cs (0.2 ppb)-Ba (1 ppb) Sensitivity enhancement 11 times Eliminate/reduce polyatomic interferences in ICP-MS/MS 95,97Mo40Ar interference

Best condition:

N2O Flow rate 50% (0.5 mL/min)

Interferences from95 Mo40Ar+ and 97Mo40Ar were negligible

97Mo40Ar+

95Mo40Ar+

Intensity (cps) Intensity

N2O flow rate (%) (100 % equal to 1 mL/min)- fourth cell Eliminate/reduce polyatomic interferences in ICP-MS/MS 119 16 121 16

Sn O and Sb O interferences Production proportions

Intensity (cps) Intensity

N2O flow rate (%) (100 % equal to 1 mL/min)- fourth cell

Best condition: N O Flow rate 50% 2 (0.5 mL/min)

Interferences from SbO+ and SnO+ were Intensity (cps) Intensity negligible

N2O flow rate (%) (100 % equal to 1 mL/min)- fourth cell 135Cs and 137Cs analysis using ICP-MS/MS

̴ 10-10 Theoretically 10-14 (10-7x10-7) 135Cs and 137Cs analysis using ICP-MS/MS

ICP-MS/MS

APEX-ICP-MS/MS Detection limit (calculated based on 1 g solid sample) Mass unit (pg/g) ICP-MS method 133Cs 0.9 ICP-MS/MS 0.36 APEX-ICP-MS/MS 135Cs 0.01 ICP-MS/MS 0.002 APEX-ICP-MS/MS 0.05 Aridus-SF-ICP-MS 137Cs 0.006 ICP-MS/MS 0.002 APEX-ICP-MS/MS 0.05 Aridus-SF-ICP-MS Aridus SF-ICP-MS data cited from Russell et al. 2014 Analytical method validation: reference materials 137Cs activity: 23 – 1142 Bq/kg

Global fallout For the first time,

137 Fukushima accident Cs 28 Bq/kg ICP-MS realized the detection of global fallout level soil sample!

Fukushima accident Irish seawater IAEA-443

Fukushima accident Irish sea APEX-

Csratio atom 137 Cs 23 Chernobyl 137 Global fallout accident Fukushima accident Cs/ TIMS data Irish sea 135 from Snow et al. Chernobyl accident 2014, 2015

Chernobyl accident Contents ■Development of advanced mass spectrometric techniques for radionuclide (actinides, Cs) analysis • Sensitivity improvement • Chemical separation development

■Pu isotopes as geochemical tracer: transport process in the ocean

■Tracing Fukushima nuclear accident released Pu and Cs isotopes in the environment

31 Pu isotopes as geochemical tracer: transport process in the ocean

Nuclear Weapons testing in Bikini Atoll in 1954 (Bravo thermonuclear detonation, 15 MT)

Sources of Pu isotopes in the NW Pacific?

Global fallout Pacific Proving Ground close-in fallout

32 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Isotopic signature of plutonium in Sagami Nada Pu isotopic compositions Okhotsk NW Pacific and its Sea in the deep layer sediment marginal seas (18-20 cm), we found: Japan Sea East China Sea 240 239 Pacific Ocean Pu/ Pu ratio 0.27-0.30 Bay Tokyo 241Pu/239+240Pu activity ratio 25.0 (in the 1950s) Sagami Nada 137Cs KT91-03-8 KT90-04-2 240Pu/239Pu 239+240Pu

KT91-03-P 20 0.32 KT91-03-6 Bikini close-in fallout ratio 1950s Sagami Trough 15 1963 0.28 PPG (Marshall Islands Tests) 240 239 KT90-04-3 Pu/ Pu ratio 0.30-0.36

10 0.24

Pu RATIO RATIO Pu Pu

Pu RATIO Pu 241Pu/239+240Pu activity ratio

239 239 239

Pu ACTIVITY (mBq/g) (mBq/g) ACTIVITY ACTIVITY Pu Pu

Pu ACTIVITY (mBq/g) ACTIVITY Pu  27 (Koide et al., 1981)

Pu/ Pu/ Pu/

240 240

5 0.2 240

239+240239+240 239+240 Global fallout ratio Sedimentation rate: 0.4 cm/y

210Pb dating

Cs and and and Cs Cs

Cs and and Cs 0 0.16

137 137 137 0 5 10 15 20 25 30 DEPTH (cm) Sedimentation rate 0.4 cm/y, 210Pb dating 33 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Continuous supply seawater with higher Am/Pu ratio Enhanced particle scavenging Vertical profiles between Pu 241Am increase after deposition and 241Am in Sagami Nada

Pu 14 241 Mainly 241Am growth Am

after deposition

/g) Estimate the release date of Pu 12 and less particle 239+240 241 1 (λ1 - λ2) A2(t)

mBq scavenging Am T = ln [ 1+ ]

) and ) 10 λ A (t)

λ1 - λ2 2 1 Pu ( Pu

Am to to Am 8

241

239+240 mBq/g Pu activity activity ratio Pu 239+240 6 Pu λ1 (0.0483), λ2 (0.0016)

Am & & Am 241 239+240 A2(t) ( Am, 5.03 ± 0.37)

241 4 241

241 239+240 A1(t) ( Pu, 9.72 ± 1.88)

Am/ of of

Am/ Pu Activity ( Activity

241 2 and and

activity ratio of activity 0 Release date: 1949 ±4 y Activites 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 Depth (cm)

Zheng and Yamada, ES & T, 2004; J. Oceanogr. 2008 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Transport of PPG close-in fallout Pu in the NW Pacific

Hypothesis Direct atmospheric deposition ??? Transportation via Oceanic 240Pu/239Pu atom ratio in soils in process, Japan: Advective lateral transportation, (Muramatsu et al., JAAS, 1999; JRNC, boundary scavenging??? 2003) Water column

0.168 — 0.181 surface soils 0.168 --- 0.194 0-30 cm vertical profile

agrigation 240Pu/239Pu atom ratio in lake aggregation settling sediments in Japan:

Japan Sea East China Sea disagrigationdisaggregation 0.186  0.016 Lake Obuchi Kuroshio Current ( Zheng & Yamada, JEM. 2005) N. Equatorial Current Sediments 0.182  0.005 Lake Towada Pu Highly sensitive analytical technique (Otsuka et al., JRNC, 2004) Enewetak Bikini is required for trace level Pu isotope ratio measurement in: Settling particles seawater

35 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

First dataset on Pu isotopic composition in setting particles in the world

36 Zheng and Yamada, ES & T, 2006 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

South China Sea and Sulu Sea Dong, Zheng* et al., JER., 2010

Okhotsk Sea Sediments 2014 Japan Sea sediments Zheng and Yamada, Sci. Total Environ. 2006 Zheng and Yamada, JRNC, 2006 Yangtzer River Estuary Sediments

2011

37 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Increase of Pu inventory in water column Evidence of PPG Pu transport Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Distribution 200 km Water column of Pu in the 0.18-0.20 Sediment column

western NW 0.15-0.18 Pacific 0.20-0.22 Oyashio current 0.22-0.23 0.22-0.24 Before the 0.20 0.21-0.26 0.20-0.27

0.19-0.26 - Fukushima 0.21 0.22-0.24 0.22-0.30 0.21-0.24 DNPP Kuroshio current 0.24-0.26 accident 0.21-0.33 0.23-0.32

0.18-0.21 Baseline 0.23-0.28 240 239 Pu/ Pu ratio North Equatorial Current 0.24-0.39

Bikini 0.150-0.281 Enewetak NW Pacific 0.26-0.28

Sources of Pu in the North Pacific: Global fallout and PPG fallout 240Pu/239Pu atom ratio: 0.18 0.30-0.36

Zheng et al., Geochem. J., 2012 39 Pu同位体比によるPu isotopesPuの海洋輸送プ口セスの解明および地球化学的トレーサーとしての as geochemical tracer: transport process in the ocean 利用

Pu atom ratios in the surface sediments for the Japanese estuaries

CM-06-09 Estuary

CM-04 Mogami River Estuary Estuary Estuary Estuary Gono River Naka River Estuary Estuary Oi River Estuary Yoshino Estuary Kuma River River Estuary Estuary Kako River Estuary SST-3 Hiroshima Bay Oyodo River Estuary SST-4

240Pu/239Pu atom ratio range: 0.170-0.270 Mean 240Pu/239Pu atom ratio in the Pacific side: 0.231

Important baseline data of Pu isotopes for radiological assessment of the impact of Fukushima nuclear accident in the marine environment

Bu, Zheng* et al., Biogeosci., 2014 40 Contents ■Development of advanced mass spectrometric techniques for radionuclide (actinides, Cs) analysis • Sensitivity improvement • Chemical separation development

■Pu isotopes as geochemical tracer: transport process in the ocean

■Tracing Fukushima nuclear accident released Pu and Cs isotopes in the environment

41 Fukushima Daiichi Nuclear Power Plant

Six boiling water reactors in FDNPP Four reactors (U1-U4) were destroyed by the accident

U1-U3 operating at the time of the earthquake and tsunami U4 fuel had been removed and stored in cooling pools

U1-U3 nuclear fuel 256 metric tons which includes 5.5 tons MOX fuel Spent fuel pools (SFP) in the four destroyed reactor buildings contained additional 461 metric tons fuel

Release sources 1. Fuel in the damaged reactor core 2. Fuel in the spent fuel pool (SFP) 气冷堆 沸水堆 压水堆 核电站Power plant 切尔诺贝Chernobyl利核事故 accident 福岛核事故Fukushima nuclear accident

USA太平洋 PacificPPG核试验场 Proving Ground (PPG) 全球沉降Global平均值 fallout 核武器Nuclear weapon grade

0 0.2 0.4 0.6 0.8 1.0 240Pu/240239Pu/Pu239 atomPu 原子比 ratio

42 200 km 100 km

Mito

Kamagaya Chiba (NIRS)

S3 30 km S2 20 km

S1

Fukushima DNPP

J-Village Tracing Fukushima nuclear accident released Pu and Cs isotopes in the environment

Isotopic evidence of Pu release from the FDNPP

Zheng et al., Sci. Rep. 2012 44 福島Tracing原発事故由来 Fukushimaの nuclear人工放射性核種 accidentの released放出源解明 Pu とand環境動態 Cs isotopes解析の in新 theトレーサー environmentの確立

Yang, Zheng* et al., Sci. Rep. 2015 http://fukushima.jaea.go.jp/initiatives/cat03/entry03.html 福島Tracing原発事故由来の人工放射性核種 Fukushima nuclear accidentの released放出源解明と環境動態 Pu and Cs isotopes解析の in新トレーサー the environmentの確立

Pu isotopic fingerprint for source identification

240Pu/239Pu 241Pu/239Pu 241Pu/239+240Pu 238Pu/239+240Pu atom ratio atom ratio activity ratio activity ratio

Global fallout 0.180±0.007 0.00194±0.00014 1.2 (2011/3/15) 0.026

Atmospheric fallout 0.1922±0.0044 0.00287±0.00056 1.86 (2000/1/1) 0.037 1963-1979 in Japan

Nagasaki A-bomb 0.028 – 0.037 0.00073 1.21 (1945/8/9) 0.074±0.001

Pacific Proving Ground 0.30 – 0.36 0.0057 (2005) 27 (1952-1954) 0.001 – 0.014

Chernobyl accident 0.408±0.003 0.123±0.007 83 (1986/5/1) 0.5

FDNPP accident 0.323-0.330 0.128-0.135 108 (2011/3/15) 1.07-2.89

Data for global fallout are cited from Kelley et al. 1999; Holm, 1988. Data for atmospheric fallout in Japan (1963-1979) are cited from Zhang et al. 2010 and Otsuji-Hatori et al. 1996. Data for Nagasaki A-bomb are cited from Yamamoto et al. 1983. Data for Chernobyl accident are cited from Muramatsu et al. 2000; Ketterer et al. 2004; IAEA, 1986; Hirose et al., 2001. Data for the Pacific Proving Ground are cited from Muramatsu et al. 2001; Diamond et al. 1960; Koide et al. 1985; Lee et al. 2005. Data for Fukushima accident are cited from Zheng et al., 2012.; TEPCO, 2012. New FDNPP Pu isotope ratio measurements: Yamamoto et al., J. Environ. Radioact. 2014 240Pu/239Pu ratio Schneider et al., Sci. Rep., 2013 241Pu/239Pu ratio Shinonaga et al., ES&T, 2014 Evrard et al., ES&T, 2014 46 福島Tracing原発事故由来の人工放射性核種 Fukushima nuclear accidentの released放出源解明と環境動態 Pu and Cs isotopes解析の in新トレーサー the environmentの確立

Zheng et al., EST Critical review, 2013 47 福島Tracing原発事故由来の人工放射性核種原発事故由来 Fukushimaの nuclear人工放射性核種 accidentの released放出源解明と環境動態解明 Pu とand環境動態 Cs isotopes解析の in新トレーサー新 theトレーサー environmentの確立

Estimation of the amounts of Pu isotopes released FDNPP accident Chernobyl METI calculated Estimation of this study Amount of released (Bq) Pu-239+240 8.7x1013 6.4x109 1.0x109 – 2.4x109 Pu-241 7.2x1015 1.2x1012 1.1x1011 – 2.6x1011 Pu-238 3.5x1013 1.9x1010 2.9x109 – 6.9x109

Pu inventories at reactors (Bq) at the time of accident initiation Pu-239+240 2.4x1015 --- 8.3x1015 Pu-241 1.9x1017 --- 7.0x1017 Pu-238 1.0x1015 --- 1.1x1016

Percentage of core inventory released (%) Pu-239+240 3.5 --- 1.2x10-5 – 2.9x10-5 Pu-241 3.5 --- 1.6x10-5 – 3.7x10-5 Pu-238 3.5 --- 2.0x10-5 – 4.7x10-5

A rough estimation on the amounts of atmospheric release of Pu isotopes based on 137Cs/239+240Pu activity ratios observed in litter samples in 20-30 km zones to the total amount of 137Cs released estimated by METI and Stohl et al. 2011, and 238Pu/FDNPP239+240Pu released activity ratioPu: 4of orders 2.9 observed of magnitude in environmental lower than samples Chernobyl accident

Zheng et al., Sci. Rep., 2012; ES&T 2013 48 福島原発事故由来の人工放射性核種の放出源解明と環境動態解析の新トレーサーの確立 Pu isotopes in seawater samples (5 – 1600 km) off Fukushima coast Bu, Zheng* et al., J. Nucl. Radiochem. Sci. 2015 No observable increase of Pu activity and change of 240Pu/239Pu atom ratio

事故前海水

Oikawa et al., 2015 福島Tracing原発事故由来の人工放射性核種 Fukushima nuclear accidentの released放出源解明と環境動態 Pu and Cs isotopes解析の in新トレーサー the environmentの確立 Pu contamination in Ocean was negligible

(2011-2013) >200 samples

Source identification of Pu in marine sediments off Fukushima coast 5 km--220 km

0.20 FDNPP source 0.0030 0.16

0.0025 PPG Yamamoto et al., 0.12 Fukushima

0.0020 sediments

0.08 0.0015 Global 0.04 fallout 0.0010 PPG source GF 0.00 0.0005 0.16 0.20 0.24 0.28 0.32 0.36 0.40 0.16 0.20 0.24 0.28 0.32 0.36 0.40 0.44 0.48 240Pu/239Pu atom ratio 240Pu/239Pu atom ratio Bu, Zheng* et al., ES&T, 2014b 50 福島Tracing原発事故由来の人工放射性核種 Fukushima nuclear accidentの released放出源解明と環境動態 Pu and Cs isotopes解析の in新トレーサー the environmentの確立 Further source identification Cs isotopes (135Cs/137Cs) in litter in Fukushima

0.360 15 March,0.002 2011 Wet-precipitation Reactor 2 release? 0.359 0.005

0.351 0.009

20-21 March, 2011 51 Wet-precipitation, Reactor 2, Reactor 3? 福島原発事故由来の人工放射性核種の放出源解明と環境動態解析の新トレーサーの確立

135Cs/137Cs in litter and in reactor core & SFP

Comparison of 135Cs/137Cs isotopic ratios observed in litter and lichen samples and those in nuclear fuels in the damaged reactors (core-1, core-2 and core-3) and in the spent fuel pools (SFPs) based on the model calculation of inventory (Nishihara et al., 2012). Zheng et al. ES&T, 2014 52 福島原発事故由来の人工放射性核種の放出源解明と環境動態解析の新トレーサーの確立

Reactor unit 2 as the major release source for Cs deposition in the NW of the FDNPP

Comparison of Cs and Pu isotopic compositions among litter (S2 and S3) and surface soil (S6) samples, nuclear fuels in the damaged reactors and in the SFPs.

53 Releases from Reactor 2 0.33-0.36

0.36-0.38

Releases from Reactor 1

Pink squares represent river suspended particles (Cao et al. Talanta, 2016) Yellow circles represent soil and litter samples (Zheng et al. ES&T, 2014) White triangles represent soil samples (Yang et al., Anal Chim Acta, 2016) Orange circles represent grass and moss samples (Shibahara et al., JNST, 2014) 福島Tracing原発事故由来の人工放射性核種原発事故由来 Fukushimaの nuclear人工放射性核種 accidentの released放出源解明と環境動態解明 Pu とand環境動態 Cs isotopes解析の in新トレーサー新 theトレーサー environmentの確立 Cs isotope ratio as a geochemical tracer 134Cs, 136Cs are difficult to be measured in the future Need new “tracer” to study environmental behavior and fate of the FDNPP-sourced radioactive Cs isotopes: 135Cs/137Cs new tracer

Kumamoto et al. Sci. Rep. 2014 134Cs/137Cs activity ratio as a tracer to understand the transport and fate of Fukushima-sourced 137Cs in the Pacific courtesy of Dr. M. Aoyama

134Cs 2.06 year 136Cs 13.2 day 137Cs 30.2 year 135Cs 2.3E6 year 55 Thank you very much! ご清聴ありがとうございました

This work was supported by the Kakenhi Grant-in-Aid for Scientific Research on Innovative Areas (24110004), the JSPS KAKENHI (grant number JP17k00537, 17H01874) and partly supported by the Agency for Natural Resources and Energy, the Ministry of Economy, Trade and Industry (METI), Japan, and the Grant of Fukushima Prefecture related to Research and Development in Radiological Sciences.