The Comparison of Composite and Conventional Materials in the Bicycle Industry used

Tato závěrečná práce shrnuje základní informace o tradičních materiálech určených na výrobu cyklistických rámů v porovnání s kompozitními materiály. Popisuje mechanické vlastnosti, technologické vlastnosti, způsob tváření a tepelného zpracování jednotlivých slitin. Informuje o jejich použití ve veloprůmyslu.This final thesis summarizes the basic information on traditional materials for the manufacture of bycicle frames in comparison with composite materials. It describes the mechanical properties, technological characteristics, methods of forming and heat treatment of alloys. It informs of their use in bicycle industry.

NEUTRONIC ANALYSIS OF THE CANDIDATE MULTI-LAYER CLADDING MATERIALS WITH ENHANCED ACCIDENT TOLERANCE FOR WWER REACTORS

The paper summarizes preliminary results of neutronic analysis of candidate ATF cladding materials that are under development at the CTU in Prague. To evaluate basic neutronics-related characteristics the Serpent code was used which is a Monte-Carlo based simulation tool. A model of WWER fuel was developed and basic neutronic analysis performed. All coating materials entail certain reactivity penalty compared to reference uncoated cladding that was quantified. The coating of cladding affects also other neutron-physical parameters of cores that modify the performance of the WWER reactors that are discussed

HEAT TRANSFER MODELLING OF TWO-PHASE FLOW IN ISOLATED CHANNEL

This paper deals with Post-CHF (critical heat flux) heat transfer with the focus on different regimes of film boiling. The new thermal-hydraulic code TUBE 2.0 is presented. This code uses the equation of energy conservation and predefined correlations to establish wall temperature, the departure of nucleate boiling ratio as well as other parameters of cooling in a simple geometry - an isolated channel. With experimental data of inverted annular film boiling from Stewart, the best-performing correlation for calculation of post-CHF heat transfer in the channel was determined. Finally, the new presented code TUBE 2.0 and subchannel code SUBCAL owned by Chemcomex a.s. are compared using results of various experiments conducted by Becker. Data from Stewart could not be used because of inability to predict the onset of boiling crisis with several correlations

THERMAL ANALYSIS OF DRY STORAGE AND TRANSPORTATION CASKS CASTOR USING COBRA-SFS

State Office for Nuclear Safety is a regulator body in the Czech Republic handling also licensing of storage and transportation casks (SCs) of the spent nuclear fuel (SNF). One of the main concerns for the dry storage of SNF is the safe removal of the residual heat resulting from the decay of fission products, actinides, and activated construction materials. There are many storage systems in use around the world with different storage configuration, fuel designs and boundary conditions that need to be evaluated. Two thermal models of SNF storage casks CASTOR 440/84 and CASTOR 440/84M were developed using the COBRA-SFS code, which is an internationally accepted and validated code used for licensing of dry storage casks and safety evaluation. The casks are in operation at the Nuclear Power Plant Dukovany for dry storage of the WWER-440 SNF. Both models were validated and used for evaluation of several problems in different configuration and particularly for licensing purposes at the SUJB

Assessment of Accident-Tolerant Fuel with FeCrAl Cladding Behavior Using MELCOR 2.2 Based on the Results of the QUENCH-19 Experiment

To ensure the applicability of accident-tolerant fuels, their behaviors under various accidental conditions must be assessed. While the dependences of the behavior of single physical parameters can be investigated in single- or separate-effect experiments, and more complex phenomena can be investigated using integral-effect tests, the behavior of an entire system as complex as a nuclear power plant core must be investigated using computer code modeling. One of the most commonly used computer codes for the assessment of severe accidents is MELCOR 2.2. In version 18019, the authors enabled the modeling of the behavior of the nuclear fuel with FeCrAl cladding (namely, alloy B136Y3) for the first time, using the GOX model. The ability of this model to reasonably accurately predict the behavior of FeCrAl cladding in accident conditions with quenching was verified in this work by modeling the QUENCH-19 experiment carried out in the Karlsruhe Institute of Technology on the QUENCH experimental device and by subsequent comparison of the MELCOR calculation results with the experiment. This article proves that the GOX model can be used to evaluate the behavior of FeCrAl cladding and that the results can be considered conservative

High-Temperature Oxidation of Chrome-Nickel Alloy

The investigations in this paper deal with the Cr-Ni alloy. The material has been recently proposed as a potential ATF concept, primarily due to its behaviour under high-temperature oxidation. A set of experiments to determine the melting point and describe the oxidation kinetics of the Cr-Ni alloy were performed in Karlsruhe Institute of Technology. Presented results reveal its superb oxidation resistance comparing to zirconium alloys. Therefore, the alloy has a great potential for nuclear applications

Effect of heat-treatment on material properties of L-DED printed austenistic alloy 08CH18N10T for nuclear reactor applications

This paper deals with the evaluation of material properties of the additively manufactured austenistic alloy 08CH18N10T, which is widely used in the Czech Republic nuclear power plants Temelín and Dukovany and other VVER reactors around the world. For purposes of utilization of additive manufacturing technologies for nuclear core components fabrication, two sets of samples were prepared from horizontally and vertically L-DED printed blocks from 08CH18N10T material. Experiments such as microstructure analysis, porosity and Vickers hardness were then performed on L-DED printed and heat-treated 08CH18N10T material, and the obtained material properties were then compared with the properties of L-DED printed 08CH18N10T material without heat-treatment for examination of its effect and also with material properties of conventionally made 08CH18N10T material

COATED CLADDING BEHAVIOR DURING HIGH-TEMPERATURE TRANSIENTS

The concept of accident-tolerant fuels has been proposed and widely investigated over the past decade. The contribution is focused on one of the near-term approaches - the modification of the surface of existing Zr-alloy claddings by protective coatings. The studied specimens are based on Zr-1%Nb substrate with chromium coating, multicomponent chromium nitride and chromium coating and multi-layer chromium nitride/chromium coating deposited by a physical vapor deposition process. Thermomechanical tests were designed to understand the cladding deformation and the burst conditions during the LOCA phenomena. Presented results show both the positive and the negative effect of coating on cladding behavior. All coatings exhibited a reduction of ballooning size and prolongation of time to burst. On the contrary, coating can be connected with larger opening size after burst, higher hydrogen content and deterioration of the local mechanical properties