Igor Brovchenko , Vladimir Maderich ,

1. Radionuclide transport modelling Igor Brovchenko, Vladimir Maderich, Institute of Mathematical Machine and System Problems, National Academy of Sciences of Ukraine, Ukraine K.T.Jung, K.O.Kim Korea Institute of Ocean Science and Technology, South Korea

2. Main applications of SELFE/SCHISM: • Sediment transport (Yellow Sea) • Radionuclide transport (Fukushima) • Stratified flows (Weddel Sea) • Lagrangian particle tracking models: • Oil spills • Sediments • Radionuclides

3. Model of radionuclide transport

4. Observed vertical profilesof 137Cs in bed sediments around the Fukushima NPP Closest to NPP point Black, Buesseler 2014

5. Observed vertical profilesof 137Cs in bed sediments around the Fukushima NPP July 2012 February 2012 Ambe et. al. 2014

6. Multylayer bed sediment and radionuclide model

7. Tortuosity is the ratio of the length of the curve (L) to the distance between the ends of it (A-B) Tortuosity factor can be related with porosity of medium Boudreau, 1997

8. Radioactivity model equations in water column - dissolved radionuclide in water, Bq/m3 - particulated radionuclide on i-th suspended sediments, Bq/m3 - settling velocity of i-th suspended sediments, m/s - concentration of suspended sediments, kg/m3 - distribution coefficient between dissolved and particulated phases - desorption rate, 1/s

9. Governing equation for the bed sediments Upper layer thickness: Upper layer fractions: Upper layer porosity: Lower layers fractions And porosity: -bed layer thickness -mass fraction of sediment of class I in the bed layer j -porosity in the layer j

10. Radionuclide transport model equations for bed layers

11. Exchange between water column and bottom sediments Shaw and Hanratty (1977) is Schmidt number, u* is friction velocity Exchange rate corrected for rough bottom is Reynolds number

12. Migration of radionuclides in bed sediments in laboratory experiment Concentration profiles in pore water Concentration profiles in sediments J. Smith et. al. 2000

13. Channel flow morphology processes Cs inflow = 1.e+6Bq/m3, for t<14days Cs inflow = 0. for t > 14days • Scenarios: • One fraction of sediments, no erosion-deposition • One fraction of sediments, erosion- deposition • Three fractions of sediments, no erosion-deposition • Three fraction of sediments, erosion- deposition

14. Simulation of one- and three-fraction scenarios SSC Particulate Dissolved One fraction with erosion Three fractions with erosion

15. Bed surface layer concentration and inventory along the channel Concentration Inventory

16. Vertical profiles of concentration in locations along the channel

17. Application for the Fukushima Daichi NPP accident Forcing used in numerical simulations: • Open boundary: global HYCOM (UV,TS,El) • Tides: NAO99 database • Meteo: Era-Interim (temperature, wind, cloudiness, humidity, pressure) Period of simulation: 1 Jan 2011 – 30 Jun 2011

18. Scenario of direct and atmospheric release Atmospheric deposition Direct release

19. Comparison of dissolved 137Cs with TEPCO measurements

20. Evolution of bottom inventory April 6 April 1 April 11 April 21 May 1 May 11

21. Evolution of bottom contamination profiles pore water sediments

22. Evolution of bottom contamination profiles pore water sediments

23. Evolution of total inventories calculated by one-layer and multilayer models

24. Conclusions • A new 3D radioactivity transport model coupled with multiscale circulation and multifractional sediment transport modules is developed • Simulation of radionuclide migration in bed sediments is in good agreement with laboratory experiment • Redistribution of radionuclide between different fractions of sediments is far slower (10 days for 137Cs) than between water and the total concentration in the sediment (several minutes). • It was shown that multi multifractional sediment and multilayer bed representation is very important on the example of contamination in channel with depression.

26. Mutual adjustment of the concentration of radioactivity in the pore water and in the mutifraction sediment The difference between the concentration of radioactivity in the sediment fraction and the total concentration in the sediment: • Concentration in the pore water tends to the equilibrium with • characteristic time of several minutes • Redistribution of the radioactivity between fractions is much • slower, with characteristic time 10 days.

27. One-layer model of bed sediment contamination Equilibrium pore water concentration

28. Idealized case of contamination of a single sediment layer by waterthrough a diffusion mechanism

29. Radionuclide transport model equations for upper bed layer

30. Bioturbation rate j j+1 If uniform -decay of bioturbation with depth -biodiffusion coefficient in layer j

31. A hypothetical time-series record of the concentration of a solid or solute species at a chosen point in a bioturbated sediment Bernard P. Boudreau “Diagenetic Models and Their Implementation: Modelling Transport and Reactions in Aquatic Sediments” (1997)

32. Profiles of the apparent Kd calculated for the experiment J. Smith et. al. 2000 Kd slowly approaches to the equilibrium value 2 m3/kg

33. Standard diagenetic equations Boudreau, 1997

34. Types of advection in the bed sediments • Burial and compaction. Burial – moving of the sediment-water interface. Compaction – closer packing of sediment particles, caused by the weight of the overlying sediment column with expulsion of porewater. • Externally impressed flow. Pressure driven underground flows • Biological advection Boudreau, 1997

35. Diffusion fluxes a. Molecular and Ionic Diffusion b. Hydrodynamic dispersion Boudreau, 1997 c. Bioturbation – biological mixing Diffusive models and non-local models

36. Models of sorption/desorption Borretzen, Salbu, 2002

37. Comparison of total inventory with Black&Buesseler 2014 measurements