MODARIA-II Summary of work Working Group: 11-15 participants - - PowerPoint PPT Presentation

WG7 - Assessment of Fate and Transport of Radionuclides Released in the Marine Environment

MODARIA-II Summary of work

Working Group:

• 11-15 participants
• Interim meetings in

– Monaco – Vienna – Kiev

Work of the group

• Pacific Ocean scenario: Fukushima releases
• Marine kds and water/sediment interactions
• Generic NPP scenario (WG3)
• Atlantic Ocean (historical releases from reprocessing

facilities)

• Numerical schemes in Lagrangian models
• Final Report

Three papers published

• R. Periáñez, R. Bezhenar, I. Brovchenko, K.T. Jung, Y. Kamidara, K.O.Kim, T. Kobayashi, L.

Liptak, V. Maderich, B.I. Min, K.S. Suh, 2019. Fukushima 137Cs releases dispersion modelling

• ver the Pacific Ocean. Comparisons of models with water, sediment and biota data. Journal of

Environmental Radioactivity 198, 50-63.

• R. Periáñez, I. Brovchenko, K.T. Jung, K.O. Kim, V. Maderich, 2018. The marine kd and

water/sediment interaction problem. Journal of Environmental Radioactivity 192, 635-647.

• Periáñez, R., Bezhenar, R., Brovchenko, I., Duffa, C., Iosjpe, M., Jung, K.T., Kim, K.O.,

Kobayashi, T., Liptak, L., Maderich, V., McGuinnity, P., Min, B.I., Nies, H., Osvath, I., Suh, K.S., de With, G., 2019 Marine radionuclide dispersion modelling: recent developments, problems and challenges. Environmental Modelling & Software 122, 104523. Review paper.

Fukushima scenario

Direct releases (JAEA) Example of surface deposition, March 15, (JAEA, KAERI)

Simulations

FORA model surface circulation (March 2011) Box definition for model comparisons Simulations: two year-long; monthly mean circulations Transport models include an integrated BUM (3 types: equilibrium, dynamic, allometric) Model results compared with measurements in water (3 layers) sediment and biota (4 species)

Sampling points

Surface water

Zooplankton and non-piscivorous fish

Non-piscivorous fish Zooplankton

Marine kd and water/sediment interactions

• When kds are measured in the sea, samples should be taken as far as possible from radionuclide

releases: equilibrium in sediment/water tracer partition does not exist in the release area. Kd model not applicable here.

• Distribution coefficients for suspended sediments and for seabed sediment may vary in orders of

magnitude being all the environmental conditions and particle properties identical.

• It is essential to know how these measurements in sediments are carried out, i.e., only the readily

exchangeable phase is extracted or not.

• In the initial phase of an accidental radionuclide release, 1-step and 2-step models produce essentially the

same results. Thus, for rapid radioactive assessments after an emergency a 1-step model may be

• adequate. However, a 2-step model should be better used for longer-term calculations.
• A multi-layer model is required to evaluate sediment inventories of radionuclides; but a single-layer model,

adequately tuned, may produce satisfactory results for radionuclide concentrations in the surface

• sediment. This is generally the case for radioactive assessments after accidents.
• As a general conclusion for the assessment of radioactive emergencies, which imply short temporal

scales, it should be recommended to have available site-specific values of kinetic rates which could be used in radionuclide transport models.

• A semi-empirical equation has been proposed to modulate the freshwater adsorption kinetic rate, k1, due

to changes in salinity and pH

Generic NPP scenario. Releases in the Atlantic Coast of the US (WG3 scenario)

USEV contiguration POSEIDON-R configuration Three models: POSEIDON-R (IMMSP) Specific box model (USEV) Eulerian ESTE (ABmerit) Radionuclide discharges for year 2016 were provided by WG3 All required inputs from literature search (depths, water currents and fluxes, SPM, sedimentation rates…) by each modelling team Completely blind model comparisons

Results: calculated concentrations in water and sediments around the NPP

Atlantic Ocean: historical releases from reprocessing plants

Example of surface circulation from JAMSTEC OFES model (Ocean global circulation model For the Earth Simulator). Mean monthly values are used.

• Simulations about 50 year-long
• BUM included in transport models
• Models compared with measurements in MARIS

database 137-Cs releases

Example: south Norwegian Sea

But OFES does not correctly solve flux through North Strait. Other options tested:

HYCOM results south North Sea

Surface water Deep water Sediment Dover Strait flux is not correctly solved FIOCOM model (First Institute of Oceanography, China) does not improve Too coarse resolution? Tide residuals in the Irish Sea are relevant? Measurements: MARIS database

Numerical schemes in Lagrangian models

One dimensional transport in a tidal channel Compare interpolation schemes Effect of dx when concentrations are calculated

⃗ r (t +Δt)=⃗ r (t)+⃗ q Δt

Model comparisons

Single particle: Initial deposition and mixing added:

Final Report

1) Introduction 2) Fukushima NPP accident scenario. Large scale simulations and biota transfer of 137-Cs 3) The water/sediment interaction problem 4) Atlantic Ocean scenario: historical releases from European nuclear fuel reprocessing facilities 5) Testing numerical interpolation schemes in Lagrangian models. Preliminary results 6) Generic NPP scenario 7) General recommendations for the use of models in radioactive assessments after accidents in the marine environment and determination and use of kds 8) Conclusions 9) Annex: Models applied to the generic NPP scenario