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[en] Based on conservative assumption this paper proposes the hydrodynamic model of occurrence and distribution of a tsunami. Using numerical simulation authors have established possibility to reach a have height of 15 m off the Fukushima-Daiichi coast when the reduced factor of hydrodynamic resistance is 1.8 . According to the developed model, flooding possibility is defined by a site level, earthquake intensity and distance, and duration of seismic impacts
[en] Purpose of the meeting: • To review progress and milestones on all research activities; • To discuss the preliminary experimental data obtained from the Natural Circulation Loop Facility L2 in Italy constructed for the assessment of different methodologies for the evaluation of the reliability of passive safety system; • To discuss lessons-to be-learned from the Fukushima Daiichi Accident in Japan and its implications to near future R&D needs on thermal-hydraulics and reactor safety; • To develop an outline of integrated annual technical report and future collaboration plan
[en] Purpose of research coordination meeting: • To review progress and milestones on all research activities; • To discuss the preliminary experimental data obtained from the Natural Circulation Loop Facility L2 in Italy constructed for the assessment of different methodologies for the evaluation of the reliability of passive safety system; • To discuss lessons-to be-learned from the Fukushima Daiichi Accident in Japan and its implications to near future R&D needs on thermal-hydraulics and reactor safety; • To develop an outline of integrated annual technical report and future collaboration plan
[en] Highlights: • Incineration ash could be converted hydrothermally to pollucite to immobilize Cs. • Pollucite could be synthesized readily with a wide range of Cs/Si ratios. • With Ca(OH)_2 added, a tough pollucite could be used to solidify Cs-polluted RHA. • Leaching results showed that the amount of Cs leached from specimen was very low. - Abstract: The Fukushima nuclear accident in Japan on March 11, 2011 produced huge amounts of Cs-polluted incineration ashes; conventional solidification methods seem unsuitable for the treatment of large amounts of Cs-polluted ashes. A novel hydrothermal method was developed to directly convert Cs-polluted incineration ash (rice husk ash) into pollucite to immobilize Cs in its crystal structure in situ. Results revealed that pollucite could be synthesized readily over a wide range of added Cs (Cs/Si = 0.2–0.6); the addition of more Cs (Cs/Si ≥ 0.5) caused the formation of a small amount of cesium aluminosilicate (CsAlSiO_4), which exhibits poor immobilization behavior for Cs. Pollucite could be formed even for a short curing time (1 h) or at a low curing temperature (150 °C). However, a high curing temperature or a long curing time favored the formation of a pure pollucite. With the added calcium hydroxide, a tough specimen with a flexural strength of approximately 22 MPa could be obtained, which suggested that this technology may be applied directly to the solidification of Cs-polluted incineration ashes. Hydrogarnet and tobermorite formations enhanced the strength of the solidified specimens, and meanwhile the formed pollucite was present in a matrix steadily. Leaching test demonstrated that the amount of Cs that leached from the synthesized specimens was very low (0.49 × 10"−"5–2.31 × 10"−"5) and even lower than that from the reference hollandite-rich synroc (2.0 × 10"−"2), although a higher content of Cs was found in the synthesized pollucite specimens (6.0–31.7%) than in the reference (3.7%). Therefore, the hydrothermal conversion of Cs-polluted incineration ash into pollucite can be applied to immobilize Cs directly.
Analysis by the IRSN of a study having shown morphological defects in populations of Japanese firs around the Fukushima power plant - Published in Nature Scientific Reports on August 28, 2015 [Watanabe Y., Ichikawa S., Kubota M., Hoshino J., Kubota Y., Maruyama K., Fuma S., Kawaguchi I., Yoschenko V.I., Yoshida S. Morphological defects in native Japanese fir trees around the Fukushima Daiichi Nuclear Power Plant. Sci. Rep., 5, 13232; doi: 10.1038/srep13232 (2015)]
[en] After the accident at the Fukushima Daiichi Nuclear Power Plant (F1NPP) in March 2011, much attention has been paid to the biological consequences of the released radionuclides into the surrounding area. A Japanese team investigated the morphological changes in Japanese fir, a Japanese endemic native conifer, at locations near the F1NPP. Japanese fir populations near the F1NPP showed a significantly increased number of morphological defects, involving deletions of leader shoots of the main axis, compared to a control population far from the F1NPP. The frequency of the defects corresponded to the radioactive contamination levels of the observation sites. A significant increase in deletions of the leader shoots became apparent in those that elongated after the spring of 2012, a year after the accident. These results suggest possibility that the contamination by radionuclides contributed to the morphological defects in Japanese fir trees in the area near the F1NPP. This paper provides an analysis of the publication of these results by Watanabe, Y. et al. in 'Nature Scientific Reports' on August 28, 2015. The original article is attached to the document
[en] Highlights: • Particle scrubbing at the pool inlet has been measured to be over 90% whenever Stokes numbers higher than 10−2. • Mechanical removal processes like inertial impaction, are dominant in jet scrubbing, even if condensation conditions prevail. • A coherent correlation of jet scrubbing efficiency depending on Stokes number and saturation ratio has been derived. • Correlation coefficient, average relative error and physical consistency support this approach as a promising via of modeling. - Abstract: The Fukushima accident stressed the significance of suppression pools as passive systems for fission product trapping. Even though pool scrubbing was extensively investigated in the past, there are gaps in the existing data base and modeling that need to be addressed, particularly those relative to high gas injection velocities in the pool. In this paper, the main results of an experimental campaign (PSP tests) on particles scrubbing at the pool inlet region when the carrier gas forms a submerged jet (“jet scrubbing”), are presented and discussed. The tests have been conducted in the PECA-PS facility of the Laboratory for Analysis of Safety Systems (LASS) and the experimental conditions have been based on two non-dimensional variables: the Weber non-dimensional number, which has been set to values over the threshold from globule to jet regime; and the gas saturation ratio, which has ranged from under saturation to over-saturation. Jet scrubbing efficiency at the pool inlet has been measured to be over 90% whenever the gas enters the pool within the jet regime (Wetest ≥ Wec), regardless thermal boundary conditions. Analysis of gas steam content, though, has not shown any clear trend. Based on the PSP experiments and some others gathered from the open literature, a tentative correlation dependent on non-dimensional Stokes number (Stk), which accounts for inertial impaction, and saturation ratio (S), which captures diffusiophoretic deposition, has been proposed as a first step to empirically model jet scrubbing. Finally, some lessons learned for forthcoming experiments have been withdrawn, particularly concerning the high impact of hydrodynamics. This work has been done within the framework of the 7th FWP of EURATOM through the EU-PASSAM project (Grant agreement No. 323217 – Euratom 7FP).
[en] This publication summarizes the findings and conclusions of an IAEA coordinated research project (CRP) on fuel modelling in accident conditions, which was initiated under the IAEA Action Plan on Nuclear Safety following the Fukushima accident. The overall aim of the project was to analyse and better understand fuel behavior in accident conditions, with a focus on loss of coolant accidents. In the course of the project the participants used a mixture of data derived from accident simulation experiments, in particular data designed to investigate the fuel behaviour during design basis accident and design extension conditions. They carried out calculations on priority cases selected from a matrix of cases identified at the first research coordination meeting and designed to support their individual priorities. These priority cases were chosen as the best available to help determine which of the many models used in the codes best reflect reality. The CRP provided an ideal platform to compare their code results with others and especially with experimental data, to which they otherwise would not have had access. The achievements made within this CRP fostered new collaborations and enhanced the development and improvement of common models and highlighted differences in the interpretation of some experiments and therefore in the use of the codes - the so-called user effects.
[en] As part of the efforts to understand the unexpected ''self-regulating'' mode of the RCIC (Reactor Core Isolation Cooling) systems in Fukushima accidents and extend BWR RCIC and PWR AFW (Auxiliary Feed Water) operational range and flexibility, mechanistic models for the Terry turbine, based on Sandia's original work , have been developed and implemented in the RELAP-7 code to simulate the RCIC system. In 2016, our effort has been focused on normal working conditions of the RCIC system. More complex off-design conditions will be pursued in later years when more data are available. In the Sandia model, the turbine stator inlet velocity is provided according to a reduced-order model which was obtained from a large number of CFD (computational fluid dynamics) simulations. In this work, we propose an alternative method, using an under-expanded jet model to obtain the velocity and thermodynamic conditions for the turbine stator inlet. The models include both an adiabatic expansion process inside the nozzle and a free expansion process outside of the nozzle to ambient pressure. The combined models are able to predict the steam mass flow rate and supersonic velocity to the Terry turbine bucket entrance, which are the necessary input information for the Terry turbine rotor model. The analytical models for the nozzle were validated with experimental data and benchmarked with CFD simulations. The analytical models generally agree well with the experimental data and CFD simulations. The analytical models are suitable for implementation into a reactor system analysis code or severe accident code as part of mechanistic and dynamical models to understand the RCIC behaviors. The newly developed nozzle models and modified turbine rotor model according to the Sandia's original work have been implemented into RELAP-7, along with the original Sandia Terry turbine model. A new pump model has also been developed and implemented to couple with the Terry turbine model. An input model was developed to test the Terry turbine RCIC system, which generates reasonable results. Both the INL RCIC model and the Sandia RCIC model produce results matching major rated parameters such as the rotational speed, pump torque, and the turbine shaft work for the normal operation condition. The Sandia model is more sensitive to the turbine outlet pressure than the INL model. The next step will be further refining the Terry turbine models by including two-phase flow cases so that off-design conditions can be simulated. The pump model could also be enhanced with the use of the homologous curves.
[en] Many methods for processing and culinary preparation of food are applied worldwide. Investigations carried out after the FDNPP accident on food processing are in general agreement with previously reported values. Some detailed information especially for the food processing methods specific to Japan have been obtained after the FDNPP accident and collated in this chapter. These data were not available at the time when IAEA TRS 472 or TECDOC 1616 were compiled. Some foods collected from forests, such as bamboo shoots and wild edible plants — known in Japan as “Sansai” — are rarely consumed in non-Asian countries, except for mushrooms and ferns. For “Sansai”, the most frequent culinary preparation methods are “tempura” (which constitutes battered and deep-fried food materials) and boiling for short time after washing. For these cooking processes only a limited reduction in radiocaesium content can be expected during cooking. Compiled data are available for a small number of food processing methods used in Japan. The low radiocaesium activity concentrations in many foods made it difficult to study the effects of food processing. However, for some products, potassium can be used as an analogue for estimating the modification of radiocaesium contents in food during processing and may be helpful in enhancing relevant data for different raw materials and food processing options in the future. More food processing data would be needed to enhance current guidance on: (a) how food processing can be used to reduce radiocaesium intakes in post-accident situations; and (b) providing more realistic estimates of internal dose.
[en] The impact of radiocaesium on mycorrhizal development and functioning of plant photosynthetic apparatus is considered. The possibility of mycorrhizal symbiosis application in phytoremediation of radioactively contaminated areas is analyzed. It is found that colonization of plants by AM fungus resulted to significant decrease of radiocaesium content in their aboveground parts, while it didn't have considerable impact on the radionuclide uptake by plant root system. AM fungi can restrict or enhance direct root uptake of radiocaesium as well as its root to shoot translocation. Radiocaesium activity concentration was considerably lower in shoots of mycorrhizal plants as compared to nonmycorrhizal ones grown on different soil types. Plant colonization with the G. intraradices resulted in 50 - 100 % decrease of radiocaesium TF from soil to aboveground biomass and 40 - 70% reduction of its translocation from plant roots to shoots. The studied plants could be potentially cultivated within areas with moderate radiocaesium contamination levels and further used in agricultural purposes. The opposite effect was observed in case of H. annuus (sunflower), where AM colonization led to nearly 10-fold increase of 134Cs activity in roots and shoots. This hyper-accumulating plant could be used in combination with AM fungi for radiocaesium phytoextraction from the soil. (authors)