Material effect in nuclear Fuel - Coolant interaction: Structural characterization of the steam explosion debris and solidification mechanism

Thesis Abstract This thesis has been performed under co-tutelle supervision between Charles University in Prague (Czech Republic) and Strasbourg University (France). It also profited from the background and cooperation of Institute of Inorganic Chemistry Academy of Science of the Czech Republic and French Commission for Atomic and Alternative energies (CEA Cadarache, France). Results of the work contribute to the OECD/NEA project Serena 2 (Program on Steam Explosion Resolution for Nuclear Applications). Presented thesis can be classed in the scientific field of nuclear safety and material science. It is aimed on the so-called "molten nuclear Fuel - Coolant Interaction" (FCI) that belongs among the recent issues of the nuclear reactor severe accident R&D. During the nuclear reactor melt down accident the melted reactor load can interact with the coolant (light water). This interaction can be located inside the vessel or outside in the case of vessel break-up. These two scenarios are commonly called in- and ex-vessel FCI and they differ in the conditions such as initial pressure of the system, water sub-cooling etc. The Molten fuel - coolant interaction can progress into thermal detonation called also "steam explosion" that can challenge the reactor or containment integrity. Recent experiments have shown that..

Selected nanoparticles systems and their physical and chemical properties

Department of Inorganic ChemistryKatedra anorganické chemiePřírodovědecká fakultaFaculty of Scienc

Selected nanoparticles systems and their physical and chemical properties

of "rigorous" work Author: MSc. Václav Tyrpekl Supervisor: RNDr. Daniel Nižňanský, PhD. Katedra Anorganické Chemie Přírodovědecká Fakulta, Univerzita Karlova v Praze Name: Selected systems of nano-particles and their physico-chemical properties Presented work belongs to the topic of solid-state chemistry, which focuses mainly on the preparation and characterization of nano-particles and nano-composites. The introduction describes current knowledge of classical magnetism and magnetism of small particles. Next paragraphs describe the sol-gel technique, which uses alkoxides of transition elements for preparation of gels, xerogels and nano-composites. The introduction ends by the overview and explanation of experimental techniques that were employed for final sample characterization. The experimental work is divided in three thematic parts: i) Preparation and characterization of CoFe2O4/SiO2 composite in the form of spheres of few microns in diameter ; ii) Preparation and characterization of Fe3O4/SiO2 composite in the form of spheres with core- shell morphology with diameter of several tens of nanometers ; iii) Preparation and characterization of Fe2O3/TiO2 composite with photo-catalytic properties. In the first part, the SiO2 micro-spheres of average 11 micrometers in diameter, doped by..

Preparation and characterization of CoFe2CoFe2O4 nanocomposites

Department of Inorganic ChemistryKatedra anorganické chemieFaculty of SciencePřírodovědecká fakult

Selected nanoparticles systems and their physical and chemical properties

of "rigorous" work Author: MSc. Václav Tyrpekl Supervisor: RNDr. Daniel Nižňanský, PhD. Katedra Anorganické Chemie Přírodovědecká Fakulta, Univerzita Karlova v Praze Name: Selected systems of nano-particles and their physico-chemical properties Presented work belongs to the topic of solid-state chemistry, which focuses mainly on the preparation and characterization of nano-particles and nano-composites. The introduction describes current knowledge of classical magnetism and magnetism of small particles. Next paragraphs describe the sol-gel technique, which uses alkoxides of transition elements for preparation of gels, xerogels and nano-composites. The introduction ends by the overview and explanation of experimental techniques that were employed for final sample characterization. The experimental work is divided in three thematic parts: i) Preparation and characterization of CoFe2O4/SiO2 composite in the form of spheres of few microns in diameter ; ii) Preparation and characterization of Fe3O4/SiO2 composite in the form of spheres with core- shell morphology with diameter of several tens of nanometers ; iii) Preparation and characterization of Fe2O3/TiO2 composite with photo-catalytic properties. In the first part, the SiO2 micro-spheres of average 11 micrometers in diameter, doped by...rigorózní práce Autor: Mgr. Václav Tyrpekl Školitel: RNDr. Daniel Nižňanský, PhD. Katedra Anorganické Chemie Přírodovědecká Fakulta, Univerzita Karlova v Praze Název: Vybrané nano-částicové systémy a jejich fyzikálně-chemické vlastnosti Předkládaná práce spadá do tematiky chemie pevné fáze a zabývá se zejména syntézou a charakterizací magnetických nano-částic a nano-kompozitů. Úvod práce popisuje současné znalosti o klasickém magnetismu pevných látek a magnetismu malých částic. Dále následuje popis metody sol-gel, která využívá alkoxidy přechodných kovu k přípravě gelů, xerogelů a kompozitních materiálů. Úvod je zakončen přehledem a výkladem experimentálních metod, které byly použity k charakterizaci výsledných produktů. Samotná experimentální práce je rozdělena do tří tematických oddílů: i) Příprava a charakterizace kompozitu CoFe2O4/SiO2 ve formě mikrokuliček o velikosti několika mikrometrů; ii) Příprava a charakterizace kompozitu Fe3O4/SiO2 ve formě kuliček s morfologií "core-shell" s velikostí několika desítek nanometrů; iii) Příprava a charakterizace kompozitu Fe2O3/TiO2 s foto-katalytickými vlastnostmi. V prvním tematickém oddílu byly připraveny mikrokuličky SiO2 o průměrné velikosti 11 mikrometrů dopované super-paramagnetickými nano-krystaly CoFe2O4. Výsledný produkt byl charakterizován...Department of Inorganic ChemistryKatedra anorganické chemieFaculty of SciencePřírodovědecká fakult

Materiálový efekt při interakcích jaderné palivo - chladící médium: Strukturní analýza úlomků parní exploze a mechanismus solidifikace

Thesis Abstract This thesis has been performed under co-tutelle supervision between Charles University in Prague (Czech Republic) and Strasbourg University (France). It also profited from the background and cooperation of Institute of Inorganic Chemistry Academy of Science of the Czech Republic and French Commission for Atomic and Alternative energies (CEA Cadarache, France). Results of the work contribute to the OECD/NEA project Serena 2 (Program on Steam Explosion Resolution for Nuclear Applications). Presented thesis can be classed in the scientific field of nuclear safety and material science. It is aimed on the so-called "molten nuclear Fuel - Coolant Interaction" (FCI) that belongs among the recent issues of the nuclear reactor severe accident R&D. During the nuclear reactor melt down accident the melted reactor load can interact with the coolant (light water). This interaction can be located inside the vessel or outside in the case of vessel break-up. These two scenarios are commonly called in- and ex-vessel FCI and they differ in the conditions such as initial pressure of the system, water sub-cooling etc. The Molten fuel - coolant interaction can progress into thermal detonation called also "steam explosion" that can challenge the reactor or containment integrity. Recent experiments have shown that...disertační práce Předkládaná disertační práce byla vypracována v rámci doktorátu "pod dvojím vedení" mezi Univerzitou Karlovou v Praze a Univerzitou ve Štrasburku (Francie). Práce využívala také zázemí Ústavu Anorganické Chemie AVČR, v.v.i a Francouzské komise pro jadernou energetiku (CEA Cadarache, Francie). Výsledky práce přispívají do projektu OECD/NEA Serena 2, zaměřeného na řešení problému parního výbuchu v jaderných aplikacích. Práce tematicky zapadá do oblasti jaderné bezpečnosti a vědy o materiálech. Hlavním zaměřením je tzv. "interakce roztaveného jaderného paliva s chladivem, která patří mezi současné vědní problémy těžkých havárií jaderných reaktorů. V případě těžké nehody jaderného reaktoru s roztavením vsádky může tavenina reagovat s chladivem (lehkou vodou), generovat velké tlakové rázy a ohrozit tím integritu jaderné nádoby nebo kontejmentu. Tato interakce může nastat uvnitř reaktorové nádoby nebo v případě jejího porušení v reaktorové šachtě. Tyto dva scénáře se lišší ve vstupních podmínkách (teplota, tlak) a mohou tedy vyvolat jiné následky. Interakce taveniny s vodou může dospět do stavu tzv. "termální detonace" nazývané také parní exploze. Současné experimenty ukázaly, že složení taveniny má významný vliv na výskyt a intenzitu takovéto exploze. Obzvláště velký rozdíl byl...Department of Inorganic ChemistryKatedra anorganické chemieFaculty of SciencePřírodovědecká fakult

Preparation and characterization of CoFe2CoFe2O4 nanocomposites

Department of Inorganic ChemistryKatedra anorganické chemieFaculty of SciencePřírodovědecká fakult

Review on high-pressure spark plasma sintering and simulation of the impact of die/punch material combinations on the sample temperature homogeneity

This paper provides a thorough review on high-pressure spark plasma sintering (HP-SPS) experiments conducted to date, with a focus on different tooling materials and their impact on microstructural, mechanical and optical properties of the resulting materials. Any SPS experiment conducted with a pressure over 200 MPa was considered as “high-pressure”. This review was supported by a comprehensive finite-element modelling study of the temperature distribution in the sample and tool set-up as a function of the used geometries, tooling material combinations, temperature window and sample material properties. The effect of the electrical and thermal conductivities of the tool and sample material on the temperature gradients in some specific sample-tool material combinations was elucidated. Electrically and thermally conductive samples in combination with SiC tools showed the lowest temperature gradients during processing, whereas electrical insulators in combination with high pressure WC, steel or TZM tools with an inner graphite die showed the smallest temperature gradients over the sample

Amphiphilic P(OEGMA-co-DIPAEMA) Hyperbranched Copolymer/Magnetic Nanoparticle Hybrid Nanostructures by Co-Assembly

This work presents the utilization of amphiphilic poly(oligo(ethylene glycol) methyl methacrylate)-co-poly(2-(diisopropylamino)ethyl methacrylate), P(OEGMA-co-DIPAEMA), hyperbranched (HB) copolymers, forming polymeric aggregates in aqueous media, as building nanocomponents and nanocarriers for the entrapment of magnetic cobalt ferrite nanoparticles (CoFe2O4, MNPs), and the hydrophobic drug curcumin (CUR) in their hydrophobic domains. Dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM) techniques were used to evaluate the multifunctional hybrid nanostructures formed in aqueous media by co-assembly of the components and their solution properties. Magnetic nanoparticles (MNPs) or MNPs/CUR were co-assembled effectively with pre-existing polymer aggregates, leading to well-defined hybrid nanostructures. Magnetophoresis experiments revealed that the hybrid nanostructures retain the magnetic properties of MNPs after their co-assembly with the hyperbranched copolymers. The hybrid nanostructures demonstrate a significant colloidal stability under physiological conditions. Furthermore, MNPs/CUR-loaded aggregates displayed considerable fluorescence as demonstrated by fluorescence spectroscopy. These hybrid nanostructures could be promising candidates for drug delivery and bio-imaging applications