Modeling the Dispersion of Radioelements from the Fukushima Power Plant into the

Sea: Methodology for an Emergency Answer, Estimation of Sources, Residence time in the Water Column and Sediment

Claude Estournel for the SIROCCO group, CNRS, Univ.Toulouse, FranceEmmanuel Bosc and Iolanda Osvath, IAEA, MonacoMarc Boquet, Victor Winiarek, CEREA, Paris Tech

presented by Patrick Marsaleix

Motivation•Request from IAEA on March 14: dispersion into the sea of radionuclides from the atmosphere and from direct release•Daily conferences with IAEA: data availability, last news…•March 24: (10 days later) first bulletin on the Sirocco website•Regular improvement of the system and the results

Material• Sirocco Ocean Model (Marsaleix et al., JAOT 2006, Ocean Modelling 2008, 2009a,b, 2011): free surface, sigma coordinate, curvilinear grid (resolution 600m to 5km)• Bathymetry : Japan Oceanographic Data Center merged with GEBCO-08 30" database• Tidal forcing :

• Sirocco Ocean Model (Marsaleix et al., JAOT 2006, Ocean Modelling 2008, 2009a,b, 2011): free surface, sigma coordinate, curvilinear grid (resolution 600m to 5km)• Bathymetry : Japan Oceanographic Data Center merged with GEBCO-08 30" database• Tidal forcing: T-UGOm (Lyard et al., 2006)

Material

• Air-Sea Fluxes: Bulk formulae (ECMWF air parameters and radiative fluxes) resolution: 3hrs, 0.25°

Motivation•Request from IAEA on March 14: dispersion into the sea of radionuclides from the atmosphere and from direct release•Daily conferences with IAEA: data availability, last news…•March 24: (10 days later) first bulletin on the Sirocco website•Regular improvement of the system and the results

Mean tidal transport (a few cm/s)

after one year of integration

MERCATORSST

NCOMSST

Material (continued)

Lateral open boundary conditions and initial state: comparison of two operational models

•MERCATOR (French operational model) used for the Sirocco bulletin•NCOM (US Navy operational model) now being tested

A higher resolution in MERCATORSimilitudes: the Kuroshyo currentDifferences: Eddies, alongshore circulation

MERCATORsurf. current

NCOMsurf. current

RADIONUCLIDES INPUT

1. Atmospheric deposit

Cumulated depositionon the sea:

2.6 1015 Bq

Outputs of the atmosph transport model Polyphemus/Polair3D (1hr, 0.25° resolution) pers. comm. M. Bocquet & V. Winiarek, Ecole des Ponts ParisTech/CEREA

Source term (on our domain)

137Cs

RADIONUCLIDES INPUT

NPP

Unknown, an a priori Cesium 137 flux is thus introduced at the coast. Following a simple inverse method (prediction/correction runs), the input flux is deduced from the nearest monitoring stations T1 and T2 (30m & 300m of NPP).

Bq/l

2. Direct liquid release

simulation

obs. at 30 and 300mof the NPP

ALONGSHORE VALIDATION

NPP

detection limit

At 10 and 16 km south of the NPP2 long series of dataGood agreement model/observation

100k

m

simulationobservation

Bq/lDaini

Iwasawa

Independent observations e.g. not involved in the calibration of the source term

Independent observations

Bq/l

NPP

VALIDATION at 3km offshoreover a ~80km north-south segment

100k

m

simulationobservation

Bq/l

No observation during the peak of release

No observation during the peak of release

No observation during the peak of release

Independent observations

Independent observations

Independent observations

VALIDATIONat 15 km offshore

NPP

100k

m

simulationobservation

Bq/l Underestimation of the simulated atmospheric deposit in the northern region ?

Independent observations

Independent observations

Source term

Cumulated release into the sea:

5.6 1015 Bq

A major result of this study: the source term of the direct liquid release137

Cs A correct agreement observation/simulation=

Confidence in the liquid source term

RESIDENCE TIME IN THE COASTAL REGION

March 20 – April 20 May 1 – May 31 June 1 – June 30

one-month averages

high inputs &strong confinement due to rather calm

wind conditions

more wind events causing dispersion

Bq/l

RESIDENCE TIME IN THE COASTAL REGION

March 20 – April 20 May 1 – May 31 June 1 – June 30

one-month averages

Stock of Cesiumin the coastal box

Songda Typhoon

ESTIMATION OF DEPOSITION OF CESIUM ON THE SEDIMENT

Based on KD=4000liter/kg (IAEA,2004), a concentration of suspended matter of 5mg/land a sedimentation velocity of ~ 1m/day (very fine suspended matter)

0.2

1

2

10

20

2.102

1.103

1.102

2.103

1.104

2.104

1.105

0.2

1

2

10

20

2.102

1.103

1.102

2.103

1.104

2.104

1.105

Bq/m2 Bq/m2

from the atmosphere from the direct release

end of June

PERSPECTIVE AT LOCAL SCALE in collaboration with Institut de Radioprotection et de Sûreté Nucléaire (IRSN)

through a PhD fellowship (We a looking for a candidate!)

Wave height calculated with the Wavewatch3 model

Songda Typhoon

take into account secondary sources •Input by rivers•Resuspension of contaminated sediments