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The marine <i>kd</i> and water/sediment interaction problem
Periá,ñ,ez, R.,Brovchenko, I.,Jung, K.T.,Kim, K.O.,Maderich, V. Elsevier 2018 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.192 No.-
<P><B>Abstract</B></P> <P>The behavior of marine distribution coefficients is analyzed with the help of numerical experiments and analytical solutions of equations describing kinetic models for uptake/release of radionuclides. The difficulties in measuring true k<SUB>d</SUB> in a marine environment perturbed by an external radionuclide source are highlighted. Differences between suspended matter and bed sediment k<SUB>d</SUB> are analyzed. The performances of different kinetic models (1-step/2step; single-layer/multi-layer) are studied in model/model and model/experiment comparisons. Implications for the use of models to assess radioactive contamination after an emergency are given; as well as recommendations when k<SUB>d</SUB> data are compiled in order to create a useful database.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Equilibrium in radionuclide partition between water and sediment seldom found in the sea. </LI> <LI> Differences between suspended matter and bed sediment kd highlighted. </LI> <LI> One step and two step kinetic models performances compared. </LI> <LI> Single layer and multi-layer models compared. </LI> <LI> Formulation to deal with changes in salinity and pH provided. </LI> </UL> </P>
Periá,ñ,ez, R.,Bezhenar, R.,Brovchenko, I.,Duffa, C.,Iosjpe, M.,Jung, K.T.,Kobayashi, T.,Lamego, F.,Maderich, V.,Min, B.I.,Nies, H.,Osvath, I.,Outola, I.,Psaltaki, M.,Suh, K.S.,de With, G. Elsevier 2016 Science of the Total Environment Vol.569 No.-
<P><B>Abstract</B></P> <P>State-of-the art dispersion models were applied to simulate <SUP>137</SUP>Cs dispersion from Chernobyl nuclear power plant disaster fallout in the Baltic Sea and from Fukushima Daiichi nuclear plant releases in the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted. Three stages which should be considered after an emergency, each of them requiring specific modelling approaches, have been defined. They are the emergency, the post-emergency and the long-term phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Models applied to simulate <SUP>137</SUP>Cs marine dispersion after nuclear accidents. </LI> <LI> Not good agreement initially found in highly dynamic environments. </LI> <LI> Difficulties in developing models for decision making after emergencies highlighted. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Periá,ñ,ez, R.,Bezhenar, R.,Brovchenko, I.,Jung, K.T.,Kamidara, Y.,Kim, K.O.,Kobayashi, T.,Liptak, L.,Maderich, V.,Min, B.I.,Suh, K.S. Elsevier Applied Science Publishers 2019 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.198 No.-
<P><B>Abstract</B></P> <P>A number of marine radionuclide dispersion models (both Eulerian and Lagrangian) were applied to simulate <SUP>137</SUP>Cs releases from Fukushima Daiichi nuclear power plant accident in 2011 over the Pacific at oceanic scale. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with <SUP>137</SUP>Cs measurements in water (surface, intermediate and deep layers), sediment and biota (zooplankton, non-piscivorous and piscivorous fish). A reasonable agreement in model/model and model/data comparisons was obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Marine dispersion models applied to Fukushima releases in the Pacific Ocean. </LI> <LI> Biological uptake model included within physical dispersion models. </LI> <LI> Model results compared with measurements in water, sediments and biota. </LI> <LI> Generally good agreement in model/model and model/data comparisons. </LI> </UL> </P>
Neutron spectrum unfolding using two architectures of convolutional neural networks
Maha Bouhadida,Asmae Mazzi,Mariya Brovchenko,Thibaut Vinchon,Mokhtar Z. Alaya,Wilfried Monange,Francois Trompier Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6
We deploy artificial neural networks to unfold neutron spectra from measured energy-integrated quantities. These neutron spectra represent an important parameter allowing to compute the absorbed dose and the kerma to serve radiation protection in addition to nuclear safety. The built architectures are inspired from convolutional neural networks. The first architecture is made up of residual transposed convolution's blocks while the second is a modified version of the U-net architecture. A large and balanced dataset is simulated following "realistic" physical constraints to train the architectures in an efficient way. Results show a high accuracy prediction of neutron spectra ranging from thermal up to fast spectrum. The dataset processing, the attention paid to performances' metrics and the hyper-optimization are behind the architectures' robustness.