Long term behavior of tritium
activity concentration in coastal
regions of Fukushima and the North
Pacific Ocean since 1970s
青山道夫
Michio AOYAMA筑波大学 福島大学
Univ. of Tsukuba Fukushima Univ.
Current status of Fukushima Daiichi
decommissioning project, treated water, and futurecollaboration among RP experts
22 June 2021 online JHPS and KARP

Objectives of this talk
• Present the long-term history of 137Cs
and 3H in the marine environment tounderstand their behavior.
• Present the Fukushima accident impact inthe marine environment based onobservations and model simulations.
• Estimate the impacts of planned tritium
release based on simple proportional
calculation and published results of modelsimulation.

Contents of this talk
• Major long-lived artificial/natural radionuclides in themarine environment• Long term behavior of 137Cs and tritium in the marine
environment at the coastal region of Japan, the Sea ofJapan, and the Pacific Ocean• A few model simulations of 137Cs and tritium• Simple proportional calculation of the possible impactof 3H release based on 137Cs observations in case ofFNPP1 accident• summaryTable 1 List of major long lived artificial/naturalradionuclides in marine environment
Fissionyield
Isotope(%)aT1/2 (yr)Radiation Sources (ranked by importance)

3H

12.32

β

Natural, Nuclear fuel reprocessing plantdischarges, Atmospheric weapons tests

14C

5.70×103βNatural, Atmospheric weapons tests

99Tc

2.11×105

β30.2γ, β2.06γ, β28.8

β129I

1.57×107γ, βb239Pu

2.41×104αAtmospheric weapons tests

240Pu

6.56×103αAtmospheric weapons tests

137Cs

5.57134Cs
90Sr

3.50

coastal discharges, atmospheric weaponstests
Atmospheric weapons tests, Nuclear fuelreprocessing plant discharges, Fukushima,
Chernobyl
Fukushima, Chernobyl
Atmospheric weapons tests, Nuclear fuelreprocessing plant discharges
Nuclear fuel reprocessing plant discharges,
NaturalAoyama, 2019, Artificial radionuclides, Encyclopedia of Ocean Sciences

4Source of radionuclides in our environment
source terms
Atmospheric weapons tests (Northern Hemisphere only)
Atmospheric weapons tests (North Pacific Ocean only)

year
1970
1970

137Cs
765+-79*
290+-30*

134Cs

90Sr
310#

Nuclear facility accidentsWindscale**Three Mile Island***Chernobyl****Fukushima (release to atmosphere)
Fukushima (direct discharge to ocean)

1957
1979
1986
2011
2011

0.044

0.00110.0002285
15-20
3.5+-0.747
1015-20 0.01-0.2###
3.5+-0.7 around 1$

Liquid effluents from nucler fuel reprocessiong plants at UK and France$$$$1970–1979
29.78
1980–1984
9.15
1985–1989
0.46
1990–1994
0.13
1995–1999
0.07
2000–2004
0.05
2005–2008
0.06

3.83
1.63
0.47
0.26
0.26
0.10
0.03

unit: PBq

3H
240000##

106Ru

131I

14
0.59
74-3700.00056
6500
1760
11000####
16020$$

0.05$$

11.7
13.6
23.6
35.4
69.4
73.1
48.9

133Xe

7.7
4.1
2.1
0.3
0.1
0.1
0.0

*:Aoyama et al., 2006 **:SCOP50 ***:THE KEMENY REPORT ON THE ACCIDENT AT THREE MILE ISLAND (October, 1979)https://tmi2kml.inl.gov/Documents/2aKemeny/Presidents%20Commission,%20Technical%20Assessment%20Task%20Force,%20Vol.%20I%20(1979-10-30).pdf ****:UNSCERA2008#:An activity ratio between 137Cs and 90Sr at Tokyo during the period from 1963 to 1965 times 137Cs amount in Aoyama et al., 2006##:Galeriu and Melintescu, 2011, global inventory ###: assumed that 137Cs vs. 90 Sr activity ratio is 100####:Report of the Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO’s Fukushima Nuclear Power Stations -, June 2011$:Povinec et al., 2012 $$:Takahata et al., 2018 $$$:Tsumune et a;., 2012. 131I/137Cs activity ratio is 5.7.
$$$$Reproduced from Table 40 in United Nations, “ANNEX C”, in Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of AtomicRadiation, 2000 Report to the General Assembly, with scientific Annexes, I, United Nations publication, Austria, 2000, 158–291 (2000) for the period from 1970 to 1994.
And, annual data was summarized from three EU reports European Commission Radiation Protection 127, 143 and 164 for the period from 1995 to 2008 (Van der Strichtand Janssens, 2001, 2005, 2010)

5Comparison of environmental
characteristics
3H137Cs• HTO• Evaporation/Precipitation• Not easy to conduct tosimulation after injected intomarine environment becauseof evaporation, precipitation.
Need to consider fresh water
flux from rivers/undergroundwater• Concentration Factor is ca. 1
for fish filet in marineenvironment ( rapidequilibrium between tissuefree water tritium, TFWT, andthe environment )• Cs+ cation: NaCl, KCl, CsCl inocean• Less mobility on land
• No evaporation,resuspension on land
• Wet and dry deposition• Easy to conduct tosimulation after injected
into marine environment
because move as seawater• Concentration Factor is ca.
100 for fish filet in marine
environment
6

137Cs activity concentration in surface water
Red: 56N at FNPP1, Fukushima coast
Black: Pacific Ocean

A figure deleted from here

Apparent half residence time of 137Cs in
the Pacific Ocean before 2011 :ca. 16 years
Left；Aoyama, 2019, Artificial radionuclides, Encyclopedia of Ocean Sciences
7right：青山、岩波科学2021年4月号

3H activity concentration in the midlatitude of western Pacific Ocean

Apparent half residence time:ca. 10 years. Less advection/diffusion compared with 137Cs which means source exist for 3H

Aoyama, M., Charmasson, S., Hamajima, Y., Duffa, C., Tsumune, D., and Tateda, Y.: Tritium
activity concentration and behaviour in coastal regions of Fukushima in 2014,8Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2021-10, in review, 2021.

Trend of tritium activity concentration in the mid latitude of the Nor
Atlantic Ocean
360 Bq m-3

240 Bq m-3
A figure was deleted from here

120 Bq m-3

Apparent half residence time:
１TU = 118 Bq m-3
ca. 10 years same as that in the NP
Pierre-Emmanuel Oms, Pascal Bailly du Bois, Franck Dumas, Pascal Lazure, Mehdi Morillon, Claire Voiseux, Cedric
Le Corre, Catherine Cossonnet, Luc Solier, Pascal Morin, Inventory and distribution of tritium in the oceans in2016, Science of The Total Environment, Volume 656, 2019,9137Cs activity concentration in surface

water in 1970-1979(left) and 2011(right)

Higher in the NH, lower in the SH
Higher close to the sources
Two figures were deleted from here

Aoyama, M., 2018. Long-range transport of radiocaesium derived from global fallout
and the Fukushima accident in the Pacific Ocean since 1953 through 2017-Part I:
Source term and surface transport, J Radioanal Nucl Chem, 318, 1519-1542. doi:
10.1007/s10967-018-6244-z

10

１TU = 118 Bq m-3

Again, Higher in the NH, lower in theSH and higher at close to the sources
regions same as the feature of 137Cs
Two figures were deleted from here

Fig. 4. Mean decay-corrected tritium
concentrations in the oceans between 0 and 500 m
depth (TU16), between years 1967 and 2016. Boxes

boundaries and decay-corrected and non- decay–corrected tritium
concentrations are listed in Table 2. If several measurements are available atone location over time, the average concentration is plotted. New tritium
concentrations from this article are represented with squares, while datacompiled from the literature are shown with circles. Nuclear power plants areindicated with red circles (data obtained fromhttp://GlobalEnergyObservatory.org).

Pierre-Emmanuel Oms, Pascal Bailly du Bois, Franck Dumas, Pascal Lazure, Mehdi Morillon,
Claire Voiseux, Cedric Le Corre, Catherine Cossonnet, Luc Solier, Pascal Morin, Inventory anddistribution of tritium in the oceans in 2016,
Science of The Total Environment, Volume 656, 201911

The features close to Japan: the SOJ (@Fukui) andFukushima coast vs. open water

3H trend in open water
12

Details of 3H trend at stations close toFukushima NPP since end of 1970s
Red: just in front ofFNPP1Blue coastal stations
close to FNPP1

Before 2011, planed 3H releasemade 3H activity concentration
as well mixed, but after theaccident 3H activity
concentration in front of FNPP1
increase sporadically due toun-controled release whilelowest activity was close tothat in open water.
Aoyama, M., Charmasson, S., Hamajima, Y., Duffa, C., Tsumune, D., and Tateda, Y.: Tritium
activity concentration and behaviour in coastal regions of Fukushima in 2014,
Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2021-10, in review, 2021.
13

Final mass balance of radiocaesium released from FNPP1 on March 2011
Radioactivity presented here are for 137Cs (134Cs) as of 11 March 2011

We know many!!

Michio Aoyama, Yayoi Inomata , Daisuke Tsumune, andTakaki Tsubono. EGU21-3885

14

Mass balance of tritium: we know a few
1.0 PBq: in the tanks

Released to the Atmosphere?

(Buesseler, 2020)

0.86 PBq (TEPCO, 2020)
2020
2011

3.4 PBq：in the three core

(Nishihara et al., JAEA-Data/Code, 2012)

1.6 PBq: in stagnant water

Atmospheric deposition in the ocean?
Land depositon(Nishihara et al., TAESJ, 2012)?

Ocean/Direct release
0.05 PBq

Inventory in the North Pacific Ocean?

(Takahata et al., 2018)

Sediment
Negligible
Coastal biota
Negligible?

?

Sea Of Japan

Back to NPO

5%?

Surface

STMW?

CMW?

North Pacific model
simulation of 137Cs (lowerpanel) and observed
activity at mid latitude of
the North Pacific Ocean(right)50 Bq m-3 at the middle ofboxes2&3 and 10 Bq m-3 at
US coast were observed.

A figure was deleted from here

50 Bq m-3

10 Bq m-3

W Middle East

16Tsubono et al., 2016 source: direct discharge and atmospheric deposition

Main surface transport pathways were Kuroshio and Kuroshio
extension, subarctic gyre and subtropical gyre. A part of released
radiocaesium was in the STMW and was transported to the SOJ.

A figure was deleted from here

青山道夫、「10年間福島事故で海洋に放出された放射性物質を追いかけて見えたこと」Isotope News No.17773、2021

Signal of Fukushima accident in SOJ:
1-2 Bq m-3 increase from 1.5 Bq m-3

A figure was deleted from hereLong term trend of 137Cs in SOJ
left：Aoyama et al., 2017, JARI right：Inomata and Aoyama, 2017 OS
Observed results in 2015

right：Data source: KINS/ER-092(2016)and previous reports

18

A comparison of simulations
137Cs
3H
50-70 Bq m-3 BG not included

Left: 1.2 PBq 1 month release
Right: 1.2 PBq 1 year release
Zhao et al., 2021, MPB. AttributionNonCommercial-NoDerivatives 4.0
International (CC BY-NC-ND 4.0)

1.5 Bq m-3 BG included

Buesseler et al., 201719
Attribution 4.0

Result of a proportional calculation : 3H vs. 137Cs in themiddle/east in the North Pacific and the SOJ
SourcePre-Fukushima 137Cs weapons tests
observation
natural, weapons tests
Pre-Fukushima 3H
observationand nuclear power plants

15-18 PBq release

direct release andatmopsheric deposition
for about one monthobservation

proportional
calculation byMA

Pacific Ocean
Bq m-3
1.5SOJ
Bq m-31.5

50-70

500-10000

10-50

1-2

one year

3-5 years

1-5

0.1-0.2

1.5 PBq release

controled releasefor one month

1.2 PBq release

controled release for one
Zhao et al.
montharound 20.01

0.1 PBq release

controled release for one
year planed by TEPCO

max. 0.33

max. 0.01

Evaluation at the coastal region
TEPCO released simulation results.

0.1 PBq y-1
BG 3H:
100 Bq m-3
includedhttps://www.tepco.co.jp/en/decommission/progress/watertreatment/images/200324.pdf
Reproduced with written permission of TEPCO dated on 21 June 2021

Evaluation at the coastal region by aproportional calculation
SourcePre-Fukushima 137Cs weapons tests
Pre-Fukushima 3H

observation
observation
natural and weapons tests (Aoyama et al.,2021)

56N at FNPP1
Bq m-3
1.567 +- 20

direct release andatmopsheric deposition
for about one monthobservation

1.5 PBq release

controled releasefor one monthscaling factor(Tsumune et al.,2012)

1.2 PBq release

controled release for one
Zhao et al.
month

not shown

0.1 PBq release

controled release for one
year planed by TEPCO

13 x 103

0.1 PBq release

controled release for one TEPCO simulation Activity>1000
year planed by TEPCO BG as 100 Bq m-3 area 30km x 2km

15-18 PBq releasescaling factor(Tsumune et al.,2012)

6.7 x 107

within a day

2.5 x 106

Other radionuclides in waters inthe tanks• 3H is not an issue regarding with release of waters
in the tanks as shown in the previous slides except
very close to the release site.
• On the contrary, other radionuclides impacts such as
C-14, I-129, Cs-137, Sr-90, Ru-106, similar toprevious releases from nuclear fuel reprocessing
plant in UK and France until the 1990s (UNSCAEAR 2000), should be evaluated before
release. The impact of Co-60 and Sb-125 should bealso evaluated.

summary137• We know what happened in the Cs case after
the TEPCO Fukushima accident based on
observations and model simulations as shown inmy talk.
• Based on the observed facts, we can evaluate theimpact of tritium releases, which is planed byTEPCO, by only doing a simple proportional
calculation without computer model simulations.
• It is safe to say for me that nobody can detect thetritium increase in open water, the North Pacific,
and the SOJ except areas very close to the releasesite.
• Close to the site, impact to community living there or doing
fisheries should be evaluated in terms of social science, not naturalscience.

御清聴ありがとうございました
Thank you for your attention!
25