FNCA 2021 Study PanelTokyo

Monitoring of environmental
changes due to nuclear techniques:
Development from radiometric analysis tomass spectrometric techniques
Katsumi Hirose
Laboratory for Environmental
Research at Mount Fuji

Climate change and environmental
impacts• Current major concern of public is climate change
and related environmental effects.
• Biosphere sensitively responds to climate change.
Severe weather, typically super typhoon, hazards
land and human society due to floods, landslideand others. Especially agriculture and fishing areseriously affected by climate change.
Sustainability of human society is closely
dependent on stable climate because ofpredictability of future environment.

Present status of climate:
Evidence of global warming

The most important point is increaseof sea surface temperature due toresponse to surface air temperature.

Environmental response to global warming

Examples: 1. rising of ocean level
2. decrease of sea ice coverageImpacts of on‐going climate change
The highest temperature (18.3 C) wasrecorded in Esperanza, Antarctica on
6 Feb. 2020.

Global warming
increasing occurrence of extreme
meteorological events
droughtdesertification
wildfires (ex. California (July‐ Nov. 200M$ lost), US; Australia(Jan. 50M$ lost))
Heavy rain floods (ex. China (June‐Oct. 320M$ lost; Japan, Kyushu(July 85M$ lost);
landslide India (June‐Oct. 100M$ lost))
Examples are severe disasters
loss of ice in polar regions rising of sea surface height
happened in 2020.
Ecological effects
Effects of biological diversity ex. decrease of coral
Decrease of water resource, decrease of agricultural
production
Human effects
Increase of heatstroke
Occurrence of pandemic of infection

Japan was the greatest economicallost in the world in 2018
due to global warming.

Assessment and prediction of futureearth environment• Long‐term monitoring of green‐house gases
CO observation in airand environmental tracers
2

started in the late 1950s

Green‐house gases: CO2, CH4, N2O, others
Environmental tracers: radioisotopes, others : next slide• Construction of climatechange history accompaniedwith social effects.
Monthly mean concentrations of atmospheric CO2
and its growth rates in Japan.

From JMA

Isotopic tracers of environment• Tracers related to meteorological parameters (temperature andhumidity)
δ18O in tree‐ring : a proxy of relative humidity and precipitation• Tracers of sources identification
Anthropogenic radionuclides (fission products, Pu isotopes, 129I, 14C
and others), stable isotopes (13C, 18O, 15N and others)• Tracers to give time scale (chronology)
Radiocarbon (14C), 210Pb, and others• Tracers of geophysical and geochemical processes
Transport of aerosols in atmosphere: anthropogenic radionuclides
Ocean circulation: 14C, 3H, 137Cs, 236U…
Solar activity: 14C, 7Be, 10Be, …
Biogeochemical processes: Pu isotopes, …
Changes of land environment (erosion): 137Cs, Pu isotopes, …
Plutonium is strongly associated with biogenic organic matter.
Cesium strongly attaches to clay minerals.

Anthropogenic activities has perturbed
isotope world
1. Atomic activities (Nuclear‐weapons testing,nuclear reactor accidents, atmospheric andocean releases of nuclear wastes, …)
new comers: 137Cs, 90Sr, 129I, Pu isotopes, …
perturbed natural isotope ratios: 3H, 14C,…

2. Non‐atomic activities (consumption of fossil
fuels, …)
Supply of dead carbon

Development of isotope analysis• Radioactivity monitoring has been developed
new techniques.
• Radiometric analysis: alpha, beta, and gamma
spectrometry from alpha, beta and gamma
counting.
• Low background measurements (undergroundfacility)• Development of mass spectrometry: Thermal
ionization mass spectrometry, ICP‐MS, AMS
As a typical example of tracers, plutonium isotopes
in environment are introduced in this presentation.

Kinds of Mass Spectrometry• Inductively coupled plasma mass spectrometry (ICP‐MS)• Accelerator mass spectrometry (AMS)
ICP‐MS and AMS are current powerful tools and installed in many
research institute of the world• Thermal ionization mass spectrometry (TIMS)TIMS: high sensitive, but less accessible• Resonance ionization mass spectrometry (RIMS)RIMS instrument is not commercial available.

• Secondary ion mass spectrometry (SIMS)• Glow discharge mass spectrometry (GDMS)SIMS and GDMS: low sensitivity (used surface analysis of high levelsamples)ICP‐MS
Target radionuclides: uranium, thorium and plutonium isotopes,79Se, 90Sr, 99Tc, 129I, 135Cs, 210Pb, 226Ra, 228Ra, 231Pa, 237Np, 241Am, 243Am, 244Cm
Detection limits: 10‐15 g – 10‐8 g, depending interferences and the sensitivity of the instrument.
Typical examples:
99Tc (T : 2.11 ×105y, beta emitter) DL: 10‐12 g (about 1 mBq) comparable
1/2

with beta counting
benefit: short time measurement, while beta counting is time consuming
Plutonium isotopes (239Pu, 240Pu, 241Pu): absolute DL: 5×10‐18 g (Aridus/SF‐ICP‐MS)
The most advantage of ICP‐MS is its ability to measure 239Pu and240Pu individually, while alpha spectrometry can be only provided
information of sum of 239Pu and 240Pu due to very close alpha energies.
135Cs (T : 2.3 ×106y, beta emitter) DL: 10 pg/L (Agilent 8800ICP‐QQQ) Ba‐free solution
1/2(135Cs: 0.41 μBq/L, 137Cs: 32 mBq/L)
theoretical 135Cs/133Cs abundant sensitivity: 10‐14Zheng et al., 2014

Sector Field‐Induced Coupled Plasma‐Mass Spectrometry (SF‐ICP‐MS)
Plutonium isotopes (239Pu, 240Pu, 241Pu, 242Pu)
analysis

Provided by Dr. Zheng

Machine performance of SF-ICP-MS(Element XR)

239Pu

Extremely low detection limit is achieved forPu isotope analysis (DL: 0.043 fg/mL){ 239Pu (0.1 μBq/mL, 240Pu(0.35 μBq/mL),
241Pu(170 μBq/mL)}
Effective sensibility: 0.005 fg (one run)

A. Element XR without Jet-interface
50µl/min nebulizer
NBS 947 100 ppq 239Pu

感度

3.5 M/ppb Pu

240Pu
241Pu

239Pu

242Pu

B. Element XR, Jet-interface, with Aridus II
50µl/min nebulizer
NBS 947 100 ppq 239Pu

感度100 M/ppb Pu

This sensitivity is the same level as that ofAMS technique.

239Pu

C. Element XR, Jet-interface, with APEX-Q
100µl/min nebulizer
NBS 947 10 ppq 239Pu

感度240Pu

60 M/ppb Pu

240Pu
241Pu

242Pu

241Pu

242Pu

Zheng, JNRS, 2015

AMS
(Ultra‐sensitive mass spectrometric technique for long‐lived radionuclides)
Target radionuclides: Radiocarbon, 129I,
10Be, 26Al, 36Cl, 129I, 41Ca, 59Ni, 135Cs, 182Hf, and actinides (236U, 239Pu, 240Pu)

Typical examples:
14C (T : 5.7 ×103y, beta emitter); AMS is the most powerful technique of 14C
1/2

measurements for radiocarbon dating.
129I (T : 1.57 ×107y, beta emitter with low energy); AMS is the only technique
1/2
enabling to measure 129I in pre‐nuclear era

samples with 129I/127I ratio (< 10‐10).
236U (neutron activation product of 235U, T : 2.34 ×107y, alpha emitter having
1/2235
similar energy with U); detection limit for 236U/238U: 10‐15
239Pu, 240Pu; detection limit for 239Pu and 240Pu: 0.5 – 2 μBq

AMS is one of the most sensitive method for Pu isotopes.
The largest benefit of AMS is downsizing of sample and short‐timemeasurement due to high sensitivity.

Plutonium in environment• The first global‐scale contamination of plutonium was occurred by
the Nagasaki nuclear explosion in 1945. Nagasaki plutonium wasdetected in ice core in the Arctic Canada.
• Major source of plutonium in the environment is global fallout due
to the 1961－62 large scale nuclear testing. Estimated total releaseof bomb‐derived 239,240Pu is 15 PBq.
• Significant amounts of plutonium dispersed in globe due to thestratospheric fallout, whereas bomb‐derived plutonium
contaminated locally.
• Plutonium deposition due to the stratospheric fallout showed atypical geographical distribution with mid‐latitude maximum innorthern hemisphere.
• Plutonium is chemically reactive element with some valences Pu(III,IV, V, VI); plutonium form stable complexes with organic ligands.
Environmental behaviors of Pu differ from those of 137Cs and 90Sr.

Plutonium isotope ratios in environmentalsamples
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‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
238Pu/239,240Pu 241Pu/239,240Pu 240Pu/239Pu
SourcesActivity ratio
atomic ratio‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Nuclear Fuel Reprocessing plants
0.25
25
Nuclear Test (1961‐62)
0.026
150.18Bikini ash0.001
260.32Weapon grade Pu
0.014
30.051
half‐life
Fallout from the 21st Chinese test 0.03
11238Pu:87.7 y
Fallout from the 26th Chinese test 0.02
5.5
239Pu:2.413x104 y
0.5
85
Chernobyl (IAEA, 1986)
240Pu:6,571 y
Chernobyl fallout (South Sweden) 0.57
85
Bikini soil
0.004
0.34
241Pu:14.4 yNagasaki soil
0.042
Irish Sea sediment
0.19‐0.22
Japanese soil
0.17
Fukushima core
2.39
0.32
Fukushima black substance
1.64‐2.64 108
0.32‐0.33_____________________________________________________________

Plutonium isotopes are a useful tracer to have better understanding on
sources and environmental changes.

Temporal variation of monthly 239,240Pu deposition observed
at Koenji (Tokyo) and Tsukuba

239,240Pu activities (sum of 239Pu and 240Pu activities)

were measured by alpha spectrometry
Hirose et al., Appl. Radiat. Isot., 66, 1975 (2008)

Temporal variations of 239,240Pu
in stratosphere and surface air

Apparent stratospheric residence
time of plutonium is 1.5±0.5 years.
●：Upper stratosphere (20 – 40 km)○： Lower stratosphere (10 – 14 km)■: surface (New York)■: Tsukuba : Milford Haven
: Prague
: Vilnius
Hirose and Povinec, Sci. Rep., 5, 15703 (2015)

Monthly 239,240Pu deposition (mBq m‐2)

Temporal variation of monthly 239,240Pu deposition at Tsukuba
3.0
2.5
2.0
1.5
1.0
0.501985

1990

1995

2000

2005

2010

Year

Marked seasonal change of 239,240Pu deposition with spring maximum was observed.
Hirose et al., 2003

Massic activity concentration of 239,240Pu (mBq g‐1)

Massic activity of 239,240Pu in deposition samples
0.5
0.4
0.3
0.2
0.101985

1990

1995

2000
Year

2005

2010

Open circle: Jan.‐May
Closed circle: June‐Dec.

Higher massic activities of 239,240Pu occurred in Kosa‐season (spring).
Especially high massic activities of 239,240Pu were observed in the early 2000s.

Outbreak of dust storm
in Chinese deserts
Dust storm in Chinese deserts occurredin spring.

Long‐range transport of Kosa (Chinese dust)

Monthly 239,240 Pu deposition (mBq/m2)

Frequency of dust storm in Chinese deserts and arid regions

noMonthly outbreak frequency of dust storm
upper: outbreak number, lower: frequency of strong wind

Kurosaki and Mikami (2003)

3.02)
-iti
sope
d04u2P,y9l
32ht
no
M

2.5

Temporal change ofmonthly 239,240Pu deposition

2.0
1.5

Seasonal changes may reflectnatural processes.

1.0
0.501990

1992

1994

1996

Year

1998

2000

2002

Hirose et al. J. EnvironMonitor(2003)

Plutonium isotopes as biogeochemical processes
What is biogeochemical process?
Biological activities are an important factor to control earth system.
Biogeochemical processes are closely related to Carbon Cycling on earth
Carbon inatmosphere

CO2 emission
Human activities

Biomass due to
Biologicalactivity

Carbon in land
Biomass
Organic carbon

Carbon in ocean
Reactive metals

Reactive metals: plutonium, thorium, iron,…

Inorganic carbon

Biomass
Organic carbon

North PacificSouth Pacific

Vertical distributions of plutonium in the ocean are controlled by biogeochemical processes:
Biological uptake, sinking of biogenic particles, decomposition biogenic particle in deeper layer.

Vertical profiles of Pu/137Cs ratios
North Pacific

Hirose, Aoyama, Povinec., JER, 2009

South Pacific239,240Pu/137Cs ratio is an indicator of biogeochemical process:Vertical transport of particles and regeneration due to biological decomposition of particles.
239,240Pu/137Cs ratios exponentially increase with depth in the ocean.

Summary• We require long‐term monitoring of anthropogenic
radionuclides to assess their radiological effects released from
nuclear facilities (nuclear reactors and others) including
accidental releases.
1．Radioactivity monitoring has provided huge amounts of timeseries data in atmosphere, land and ocean at global scale.
2．The time series data reflect environmental change due tohuman activities such as climate change, as do naturalvariations.
3. Anthropogenic radionuclides are effective tools as tracers ofenvironmental change.
4．New techniques of radionuclides with high sensitivity andhigh selectivity open new world for use of radionuclides asenvironmental tracers.

Final Remark
Climate change is a threat to sustainability ofhuman society.
The monitoring of anthropogenic radionuclides has
to effectively use for assessment of environmental effects
due to climate changes.

Thank you for your attention!
Acknowledgement:
I would appreciate providing an opportunity to participate
FNCA2021 for Mr. Sano Commissioner of JAEC and Prof. Nakanishi.
I also thank Dr. Zheng and many colleagues to provide information
on new techniques.