coastal dispersion model reliability in accidental
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Coastal dispersion model reliability in accidental situation (Fukushima, Japan), how to make the most of in-situ measurements?
Bailly du Bois P.1, Laguionie P.1, Garreau P.2, Theetten S.2
1 IRSN/PRP/SERIS/LRC Rue Max Pol Fouchet - BP10, Cherbourg-Octeville, 50130, France e-mail: pascal.bailly-du-bois@irsn.fr
2 IFREMER/DYNECO/PHYSED Technopôle de Brest-Iroise, Plouzané, 29280, France
e-mail: pierre.garreau@ifremer.fr
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 2/21
Fukushima accident in marine environment conditions▌Accident in the Fukushima Dai-ichi nuclear power plant
represented the most important artificial radioactive release flux into the sea ever known.
▌Origins of the labelling:Atmospheric fallout onto the ocean, Direct release of contaminated water from the plantTransport of radioactive pollution by leaching through contaminated soil.
▌Principal radionuclides measured: 137Cs t1/2=30 years, 131I t1/2=8 days
▌ In the vicinity of the plant (less than 500 m), concentrations in early April reached 68 000 Bq.L-1 for 134Cs and 137Cs, and exceeded 100 000 Bq.L-1 for 131I
Measurement data sources: TEPCO, MEXT, Detection limits: more than 5Bq.l-1 (monitoring measurements)
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 3/21
Hoyashio
Kuroshio
General currents (Hycom simulation)
Hydrograhic domain
Bathymetry (JODC data )
Tsugaru strait
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 4/21
Atmospheric fallout
Estimation of total atmospheric release: 11.5 PBq of 137Cs.
IRSN estimation of cumulated 137Cs deposit at 80 km of distance from Fukushima Dai-ichi plant is 3 PBqInitial ratio (131I/137Cs) = 14)
Calculated cumulate 137Cs wet deposit, April 23, 2011
140.1 140.35 140.6 140.85 141.1 141.35 141.6 141.85 142.1 142.3536.2 36.3 36.4 36.5 36.6 36.7 36.8 36.9
37 37.1 37.2 37.3 37.4 37.5 37.6 37.7 37.8 37.9
38 38.1 38.2
137Cs wet deposit
Bq.m-2
Fukushima Dai-ichi
0 20 40 60 80 100 km
N0.0E+000
2.5E+005
5.0E+005
7.5E+005
1.0E+006
1.3E+006
1.5E+006
1.8E+006
2.0E+006
2.3E+006
2.5E+006
2.8E+006
3.0E+006
3.3E+006
3.5E+006
3.8E+006
4.0E+006
140.1 140.35 140.6 140.85 141.1 141.35 141.6 141.85 142.1 142.3536.2 36.3 36.4 36.5 36.6 36.7 36.8 36.9
37 37.1 37.2 37.3 37.4 37.5 37.6 37.7 37.8 37.9
38 38.1 38.2
137Cs dry deposit
Bq.m-2
Fukushima Dai-ichi
0 20 40 60 80 100 km
N0.0E+000
3.6E+003
7.2E+003
1.1E+004
1.4E+004
1.8E+004
2.2E+004
2.5E+004
2.9E+004
3.2E+004
3.6E+004
4.0E+004
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 5/21
Seawater 137Cs concentrations, 131I/137Cs ratio*
Seawater measurements at less than 2 km from the
Fukushima Dai-ichi
power plant.
Direct release average IR* around 20
Measurements at more than 5km from the coast.
IR* 5 -
30
1E0
1E1
1E2
1E3
Cae
sium
137
, Bq/
L
0
10
20
30
40
50
60
70
80
90
Iodi
ne 1
31 /
caes
ium
137
20/03 25/03 30/03 04/04 09/04 14/04 19/04 24/04 29/04 04/05 09/05 14/05 19/05 24/05 29/05 03/06 08/06 13/06 18/06 23/06 28/06
Caesium 137, Bq/L Ratio I131/Cs137, decay corrected
1E1
1E2
1E3
1E4
1E5
Cae
sium
137
, Bq/
L
0
10
20
30
40
50
60
70
80
Iodi
ne 1
31 /
caes
ium
137
20/03 27/03 03/04 10/04 17/04 24/04 01/05 08/05 15/05 22/05 29/05 05/06 12/06 19/06 26/06
Caesium 137 Ratio I-131/Cs-137, decay corrected
*initial ratio (IR): 131I/137Cs decay corrected to the 11 March 2011
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 6/21
Estimation of the direct release source-term into seawater137Cs quantities were estimated on the basis of individual measurements in a 50 x 100 km area around the plant (issues: depth, mixing layer, atmospheric fallout, rain water washout, …)
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
April 11 - 18
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
April 18 - 25140.8 141 141.2 141.4 141.6
April 25 - May 02
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6May 02 - 16
Fukushima Dai-ichi
a b c d
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
Blue frame: area for integration of 137Cs quantities : Sampling locations
e f g hMay 16 - 30 May 30 - June 13 June 13 - 27 June 27 - July 110 km 20 km 40 km 60 km
Interpolated137Cs
concentrations from April 11
to July 11
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 7/21
Estimation of the source-term from direct releases into seawater
Measurement period Number of measurements
accounted
137Cs quantity
Begin End Middle
11/04/11 18/04/11 14/04/11 92 11.6 PBq
18/04/11 25/04/11 21/04/11 77 4.75 PBq
25/04/11 02/05/11 28/04/11 118 3.38 PBq
02/05/11 16/05/11 09/05/11 293 0.67 PBq
16/05/11 30/05/11 23/05/11 233 0.26 PBq
30/05/11 13/06/11 06/06/11 227 0.16 PBq
13/06/11 27/06/11 20/06/11 250 0.04 PBq
27/06/11 12/07/11 04/07/11 202 0.002 PBq
Quantities of 137Cs deduced from interpolation of individual measurements in seawater.
Other estimations: 1 – 4PBq (TEPCO, Tsunume et al., Kawamura et al.)
Average mixing layer thickness deduced from hydrographic measurement: 32m
NERH, 2011. Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety – The Accident at TEPCO’s Fukushima Nuclear Power Stations. NERH Report. www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.htmlTsumune D., Tsubono T., Aoyama M., Hirose K., 2011. Distribution of oceanic 137Cs from the Fukushima Daiichi Nuclear Power Plant simulated numerically by a regional ocean model. Journal of Environmental Radioactivity Volume, Issues 0. DOI: 16/j.jenvrad.2011.10.007Kawamura H., Kobayashi T., Furuno A., IN T., Iishikawa Y., Nakayama T., Shima S., Awaji T., 2011. Preliminary Numerical Experiments on Oceanic Dispersion of 131I and 137Cs Discharged into the Ocean because of the Fukushima Daiichi Nuclear Power Plant Disaster. Journal of Nuclear Science and Technology Volume 48, Issues 11, Pages 1349-1356. DOI: 80/18811248.2011.9711826
PBq: 1015Bq
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 8/21
Estimation of the rate of seawater renewal
Environmental half-time
exponential decay
t1/2 = 6.9 d
Constant dilution by clean water through marine currents due to convergence of Kuroshio and Oyashio currents
Seasonal changes in the ocean circulation ?Return of contaminated water back in the area ?
If no more releases occur and dilution remains constant, back to prior situation could be expected in Nov 2011
Exponential decay back extrapolated to April 8: 22PBq
Main incertitude: depth of the mixing layer
Evolution of 137Cs quantities measured in seawater
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 9/21
Flux estimation of 137Cs from direct releases
This source-term could be used in numerical dispersion models
Evolution of concentrations and
corresponding fluxes of 137Cs in
seawater
Assumptions:• Measurements close to the plant are representative of the released flux.• Amount of 22 PBq corresponds to the quantity of 137Cs released from March 26 to April 8
(average concentration:15 716 Bq.L-1, number of values = 28, duration = 13.2 days).• Fluxes of 137Cs could be deduced from concentrations by applying the factor:
1.06E+11 Bq released / Bq.L-1 measured
Right Y axis in figure shows this conversion.
1E1
1E2
1E3
1E4
1E5
Cae
sium
137
, Bq/
L
1E12
1E13
1E14
1E15
1E16
Cae
sium
137
, Bq/
day
20/03 27/03 03/04 10/04 17/04 24/04 01/05 08/05 15/05 22/05 29/05 05/06 12/06 19/06 26/06 03/07 10/07 17/07
30 m North of Fukushima Dai-ichi
More details in: Bailly du Bois P., Laguionie P., Boust D., Korsakissok I., Didier D., Fiévet B. 2011. Estimation of marine source- term following Fukushima Dai-ichi accident. Journal of environmental Radioactivity. DOI:10.1016/j.jenvrad.2011.11.015
Total direct release until July 18 -> 27 PBq(12 PBq -> 41 PBq)
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 10/21
Hydrodynamic models in marine accidents
▌Coastal models are key components of operational forecast systems which could be deployed during crisis such as point- source pollution incidents.
▌Model reliability can be assessed with field-based data.
▌ In this context, artificial radionuclides are exceptional validation tools because they can be measured at all scales and source-terms are generally well known.
▌The MARS (Model for Applications at Regional Scale) model was used After Fukushima Dai-ichi accident to reproduce and forecast the behaviour of contaminated waters for direct releases and deposit in Pacific ocean.
▌Dissolved 137Cs measurements allowed assessing model reliability in this low energetic tidal environment (currents of 1 m.s-1), but strong general circulation (Kurushio and Oiashio currents).
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012
Crisis modelling for Fukushima marine AccidentConstraints :
High resolution to follow the radionuclide releases
Taking into account the regional an local circulation- Kuroshio current (strong density unstable current)- The flux trough the Tsugaru Strait- The wind forcing (possibility of typhoons)- The tides (relatively low)
Use the data available in the framework of a crisis
The oceanic forecast and hindcast of global model of MERCATOR-Ocean
- resolution about 8-10 km (1/12°) - one field per day (T, S, U, V, ssh)
The atmospheric forecast and hindcast of global model NCEP- resolution about 50 km(1/2°)
Tidal Harmonic component (16) atlas FES2004 (1/8°)
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012
The FUKU0 configuration of MARS3D code
Animation of the sea surface temperature:
ftp://ftp.ifremer.fr/ifremer/dyneco/pgarreau/FUKU/film_temp.gif
Animation of current (zoom):ftp://ftp.ifremer.fr/ifremer/dyneco/pgarreau/FUKU/film_tsugaru.gif
10 000 m depth
Tsugaru strait
Fukushima power plant
Extension : 31°N - 43.2°N , 137°E - 152°E (1000km*1200km)Resolution : about 1 nautical mile (1/60°)
: 40 sigma levels refined near the surface
OBC and IC : temperature, salinity, currents, sea level from Mercator-Ocean,combined with the tidal harmonics
Run : on 256 MPI ranks
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 13/21
Model calculation of the mixing layer
Quantities of 137Cs simulated in the inventory area confirms the 32m estimation of the mixing layer for the computation of inventories.
-60
-50
-40
-30
-20
-10
0
Dep
th (m
eter
s)
0% 20% 40% 60% 80% 100%Cesium 137 inventory
Cs137 inventory in the surface layer Average thickness for calculation
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 14/21
Environmental half time
1E12
1E13
1E14
1E15
1E16
1E17
Dis
solv
ed c
esiu
m 1
37 in
the
area
20/03 30/03 09/04 19/04 29/04 09/05 19/05 29/05 08/06 18/06 28/06 Date
Simulated quantities Environmental half time of 17 daysMeasured quantities Environmental half time of 6.9 days
Model renewing time is lower than deduced from in-situ measurements
Differences between model and measurements concentrations will increase with time.It could explain why other model/measurement comparisons gives lower estimations of direct releases (Tsunume et al., Kawamura et al.). But estimation from Buesseler et al. based on other measurements confirms our order of magnitude for direct releases. Buesseler, K. O., Jayne S. R., Fisher N. S., Rypina I. I., Baumann H., Baumann Z. et al. 2012. Fukushima-derived radionuclides in the ocean and biota off Japan. PNAS 2012 109 (16) 5984-5988, doi:10.1073/pnas.1120794109.
Environmental half-times
6.9 days
17 days
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 15/21
Matching calculations / measurements
1E0
1E1
1E2
1E3
1E4
1E5
Bq/
L
28/03 04/04 11/04 18/04 25/04 02/05 09/05 16/05 23/05 30/05 06/06 13/06 20/06 27/06 04/07
Measurements Mars Simulation
Cs137
1E0
1E1
1E2
1E3
Bq/
L
28/03 02/04 07/04 12/04 17/04 22/04 27/04 02/05 07/05 12/05 17/05 22/05 27/05 01/06 06/06 11/06 16/06 21/06 26/06 01/07 06/07
Measurements Mars simulation
Cs137
Less than 1 km off the facility
More than 5 km off the facility
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 16/21
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
137Cs in surface seawater, April 11 - 18
Fukushima Dai-ichi
Measurements : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
Fukushima Dai-ichi
Simulation : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
137Cs in surface seawater, April 25 - May 02
Fukushima Dai-ichi
Measurements : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
Fukushima Dai-ichi
Simulation : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
137Cs in surface seawater, May 02 - 16
Fukushima Dai-ichi
Measurements : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
Fukushima Dai-ichi
Simulation : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
137Cs in surface seawater, May 30 - June 13
Fukushima Dai-ichi
Measurements : Sampling location
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
Fukushima Dai-ichi
Simulation : Sampling location
Matching calculations / measurementsApril, 14 April, 28
May, 9 June, 6
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 17/21
Atmospheric wet deposit
A large incertitude remain concerning parameters of wet deposit onto the sea. Results confirms the orders of magnitude used in simulation of deposit (vd=5.10-5 m/s, lambda=5.10-5 hr.mm-1.s-1)
137Cs in surface seawater, March 22
140.8 141 141.2 141.4 141.6
37
37.2
37.4
37.6
37.8
Fukushima Dai-ichi
137Cs in surface seawater, March 31
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
02468101215192329364556698610013016020025031039048060074092011001400170021002700
Bq.L-1
137Cs in surface seawater, April 7
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
137Cs in surface seawater, March 25
140.8 141 141.2 141.4 141.6
Fukushima Dai-ichi
Coloured spots: measurementsShaded background: simulation
: Sampling locationColoured spots: measurementsShaded background: simulation
: Sampling locationColoured spots: measurementsShaded background: simulation
: Sampling locationColoured spots: measurementsShaded background: simulation
: Sampling location
End of the atmospheric deposit: 16 March
After 28 March: influence of the direct release
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 18/21
Model animation
Color-scale changed by a factor 10
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 19/21
Discussion
• Association between simulations and measurements and early measurements are essential to estimate source terms.
• Why simulated renewing time is too long: wind shear stress or open condition limits?
• Studies in the English Channel and North Sea show that the wind drag coefficient is a key parameter, depending of the meteorological data applied. This question will be examined in more details.
• Before March 11 2011, direct releases to the sea was not accounted for possible nuclear power plant accidents. Generally marine systems are not the first emergency in such situations, but answers must be prepared and other situations could end up to dispersion of radionuclides (ship wreck).
• Stochastic turbulence in the Fukushima area, measurements available and poor knowledge of the source term made difficult to investigate exact location of the plume following releases.
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 20/21
Conclusions: radionuclides
• Contamination of the marine environment following the accident in the Fukushima Dai-ichi nuclear power plant represents the most important artificial radioactive direct liquid release into the sea ever known (arround 27 PBq for 137Cs only).
• Available measurements made possible to estimate the environmental half-time of the release area, and the radionuclide fluxes from direct releases.
• Due to the exceptional dilution conditions, concentrations in seawater decrease strongly at the end of 2011.
• It will be different for benthic species living close to the plant or concerned by transfer through suspended matter coming from deposited sediments, rivers or desorption in seawater of radionuclides fixed onto sediments.
• Caesium 137 and 134 from Fukushima will remain detectable for several years in the North Pacific. 137Cs/134Cs ratio could be used as a tracer for studies on water masses pathways and transit times.
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 21/21
Conclusions: hydrodynamic models
• Hydrodynamic models are essential tools to approach consequences of accidents in marine environment. It is our duty to apply them, even very far from Europe.
• Simulations during accidents are useful to : organize in-situ intervention and sampling, manage living resources and human uses of marine system, information of stakeholders and populations.
• Models made possible dynamic calculation of transfers to living species by using biological half-lives of radionuclides (if available).
• Measurements of dissolved radionuclides made possible to approach Mid- and long-term precision of hydrodynamic models.
• Measured and simulated process are comparable, some key parameters as renewing time could be improved.
• Even if few early data are available, useful orders of magnitude for atmospheric deposit parameters are provided by simulations.
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 22/21
Special thanks to:
MEXT and TEPCO for the Internet publication of the concentration data collected in the environment.
Celine Duffa, Mireille Arnaud, Olivier Connan, Vanessa Parache, Tina Odaka and “Centre Technique de Crise” staff of the French Institute of Radioprotection and Nuclear Safety for searching compiling and checking thousands of measurements.
We want to express all our sympathy to Japanese people.
Coastal dispersion model reliability in accidental situation (Fukushima, Japan) - JONSMOD2012 23/21
Inventory of main 137Cs releases in the oceans
Source PBq (1E+15Bq)
Fallout from nuclear weapon tests 704*
Nuclear fuel reprocessing 1951 - 2010
BNFL Sellafield 41.21
Areva-NC La Hague 1.04
Tchernobyl accident 16*
Solid waste dumping 41.4 (total beta + gamma)
Fukushima accident
Direct liquid release 27
Atmospheric fallout 3 (80 km radius circle)
* Aarkrog, 2003. Input of anthropogenic radionuclides into the World Ocean. Deep Sea Research Part II: Topical Studies in Oceanography Volume 50, Issues 17-21, Pages 2597-2606
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