Acta Polytechnica CTU Proceedings
type: channel
description: A peer-reviewed serial open access publication, published by the Czech Technical University in Prague, is focused on publishing proceedings from conferences organized or co-organized by the Czech Technical University in Prague. Acta Polytechnica CTU Proceedings is published in electronic version, a printed version is possible only on demand. Each individual issue can also have, besides the ISSN, their own ISBN. Acta Polytechnica CTU Proceedings is indexed by Scopus (since 2020) and DOAJ. Selected Volumes are indexed by Web of Science database. Articles are licenced under a Creative Commons Attribution 4.0 International licence
publisher: Czech Technical University in Prague
language: en
publication name: Acta Polytechnica CTU Proceedings
issn: 2336-5382
items: An evaluation of primary lining deformation using measurements with FBG sensors during a tunnel excavation
items: Special foundation of new buildings in Nové Sady Street in Brno
items: Effect of tangent and secant elastic constants on CCBO stress evaluation in transversely isotropic rock
items: Landslide mapping using drone-based method
items: Modelling diaphragm walls using a time-dependent elasto-plastic material model
items: Derivation of soil shear modulus from push and pull tests of micropiles
items: A geotechnical investigation for an office building in the foothills of the Bohemian Forest
items: Calibration of the hardening soil model in excalibre
items: Innovative approaches to a solution for surface deformations on earth structures of linear traffic construction
items: 51st and 52nd Conference Foundation Engineering Brno 2023 and 2024
items: Thermal diffusivity of ATF cladding materials using laser flash technique
items: Experimental study of the Leidenfrost effect in the context of high heat flux cooling
items: Adaptation of SUBCAL subchannel code for square-lattice rod bundles using PSBT benchmark
items: Dispersion type metal-metal based high-density fuels for nuclear reactors – sample preparation, analysis and examination of LOCA behaviour
items: Numerical simulation of secondary heat exchanger in S-Allegro
items: Subtractive gamma discrimination technique for neutron diamond detectors operating in mixed radiation fields
items: Microstructural and mechanical property characterization of high-density uranium fuel for light-water reactors
items: Project VALVERDE – validation and verification of computational tools to describe corium spill to improve deterministic analyses of severe accidents
items: Impact of fecral oxide composition on severe accident progression in MELCOR
items: High-temperature oxidation of non-zirconium materials for ATF
items: Corrosion behaviour of AISI 348 stainless steel in simulated WWER environment and during LOCA conditions
items: Post-CHF nuclear fuel operation with Time-at-Temperature criteria
items: Šimáně 2025 – International Student Conference on Nuclear Engineering
items: Experimental analysis of physical properties of lightweight gypsum plasterboard
items: A study of the behavior of samples of high-performance concrete shells with filled core exposed to compression
items: Deep learning-based modeling and simulation of heat conduction
items: Characterization of the microstructure of cement paste exposed to gamma radiation by scanning electron microscopy
items: Mechanical properties of cement composites with plasma-treated waste glass aggregate
items: Prestress load distribution modeling for containment digital twin model
items: Prestressed textile reinforced concrete with carbon composite reinforcement

An evaluation of primary lining deformation using measurements with FBG sensors during a tunnel excavation
type: item
description: The paper presents an evaluation of data gathered with the FBG (Fiber Bragg Gratings) instrument for primary lining deformation measurement, which was installed into primary lining of adit during construction. The evaluation is related to the initial shape of primary lining, and its deflection curve is computed. Definition of appropriate boundary conditions can be verified with the use of geodetic convergence monitoring results. The developed evaluation procedure can be used also for determination of Bragg wavelengths during the design of primary lining monitoring.
subject: Articles
  topic: section
subject: geotechnical monitoring
  topic: keywords
subject: underground structures
  topic: keywords
subject: primary lining
  topic: keywords
subject: fibre optics Fiber Bragg Gratings
  topic: keywords
creator: Jan Záleský
creator: Petr Mayer
creator: Michal Beneš
creator: Jiří Barták
creator: Jan Pruška
creator: Marek Záleský
creator: Zdeněk Sekyra
creator: Monika Lidmilová
creator: Ladislav Šašek
rights: Copyright (c) 2026 Jan Záleský, Petr Mayer, Michal Beneš, Jiří Barták, Jan Pruška, Marek Záleský, Zdeněk Sekyra, Monika Lidmilová, Ladislav Šašek https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 46
ending page: 51
doi: 10.14311/APP.2026.56.0046

Special foundation of new buildings in Nové Sady Street in Brno
type: item
description: The construction of the TITANIUM building was started in 2008 near the main railway station in Brno, along the left side of Nové Sady Street. This was followed by the southern extension and expansion of the IN SADY building, then the northward extension of the TITANIUM X and CENTROPOLIS buildings. Various special foundation methods were used in the construction of the building pits and the actual foundation of the buildings. Responses to the realistic form of neogenic clay were also important.
subject: Articles
  topic: section
subject: piles
  topic: keywords
subject: sheet piles
  topic: keywords
subject: Neogene bedrock
  topic: keywords
subject: groundwater
  topic: keywords
creator: Petr Svoboda
rights: Copyright (c) 2026 Petr Svoboda https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 32
ending page: 36
doi: 10.14311/APP.2026.56.0032

Effect of tangent and secant elastic constants on CCBO stress evaluation in transversely isotropic rock
type: item
description: The Compact Conical Borehole Over-coring (CCBO) method is employed for the determination of the three-dimensional stress state in rock environments. The method utilises a strain gauge cell to quantify the deformation of over-cored rock, the deformation characteristics of which are evaluated in the laboratory. It is assumed that the in situ rock material is homogeneous, elastic and transversely isotropic and it is, therefore, imperative to ascertain the deformation parameters of the transversely isotropic material present in situ. The tangent and secant deformation parameters were taken from previous research and then employed throughout the stress determination process. This paper outlines the fundamental principles of the method and presents results from practical measurements carried out at the Grimsel Underground Research Laboratory in Switzerland. The stress results vary depending on whether alternative deformation characteristics (i.e. tangent or secant) are taken into account during the evaluation process.
subject: Articles
  topic: section
subject: 3D stress state
  topic: keywords
subject: stress state in rock mass
  topic: keywords
subject: CCBO method
  topic: keywords
subject: over-coring method
  topic: keywords
subject: in situ stress
  topic: keywords
subject: determination of stress
  topic: keywords
subject: transversely isotropic rock
  topic: keywords
creator: Alice Petrlíková
creator: Lubomír Staš
creator: Alexej Kolcun
creator: Vlastimil Kajzar
creator: Petr Koníček
creator: Kamil Souček
rights: Copyright (c) 2026 Alice Petrlíková, Lubomír Staš, Alexej Kolcun, Vlastimil Kajzar, Petr Koníček, Kamil Souček https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 16
ending page: 22
doi: 10.14311/APP.2026.56.0016

Landslide mapping using drone-based method
type: item
description: The article focuses on the possibilities of landslide mapping using photogrammetric and LiDAR measurements from a drone. The measurements are then evaluated and compared with conventional methods.
subject: Articles
  topic: section
subject: territory mapping
  topic: keywords
subject: landslides
  topic: keywords
subject: photogrammetry
  topic: keywords
subject: LiDAR
  topic: keywords
subject: drone
  topic: keywords
creator: Daniel Turanský
creator: Tomáš Štor
rights: Copyright (c) 2026 Daniel Turanský, Tomáš Štor https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 37
ending page: 40
doi: 10.14311/APP.2026.56.0037

Modelling diaphragm walls using a time-dependent elasto-plastic material model
type: item
description: This paper utilizes an advanced time-dependent elastoplastic material model for the modelling of diaphragm walls via the Finite Element Method (FEM). After describing the timedependent behaviour of concrete, the Shotcrete material model is specified, and calibration of the material model in long-term conditions based on laboratory testing is carried out. Finally, a real boundary value problem of deep excavation supported by permanent diaphragm walls with the strut is solved. Various strategies of modelling are used and compared. The Shotcrete material model allows simulating creep deformations continuously (that is not stepwise), but when limiting tensile and compressive strength, it is necessary to include reinforcement.
subject: Articles
  topic: section
subject: diaphragm wall
  topic: keywords
subject: creep
  topic: keywords
subject: shrinkage
  topic: keywords
subject: material model
  topic: keywords
subject: biaxial test
  topic: keywords
subject: calibration
  topic: keywords
subject: finite element method
  topic: keywords
subject: Plaxis 2D
  topic: keywords
creator: Daniela Marková
creator: Juraj Chalmovský
rights: Copyright (c) 2026 Daniela Marková, Juraj Chalmovský https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 1
ending page: 7
doi: 10.14311/APP.2026.56.0001

Derivation of soil shear modulus from push and pull tests of micropiles
type: item
description: The article presents a method for earning soil shear modules from the results of micropile loading tests. The micropile is first loaded with a push force and then with a pull force. The shear modules are derived from two graphs of the dependence of micropile displacements on the loading forces. One represents a push and the other a pull test. Three values of soil shear moduli are obtained, namely for elastic deformation, plastic hardening and the last one after soil failure at a slip plane on micropile shaft.
subject: Articles
  topic: section
subject: soil
  topic: keywords
subject: shear module
  topic: keywords
subject: micropile
  topic: keywords
subject: load test
  topic: keywords
creator: Karel Vojtasík
rights: Copyright (c) 2026 Karel Vojtasík https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 41
ending page: 45
doi: 10.14311/APP.2026.56.0041

A geotechnical investigation for an office building in the foothills of the Bohemian Forest
type: item
description: An office building with a partial basement on an undeveloped plot within Polná na Šumave was proposed. The municipality is located on the border of Boletice Military Training Area which had some specific security measures that had to be respected during the investigation. The detailed geotechnical investigation describes the geological conditions of the area, points out several complications that can be expected and finally proposes solutions to mitigate them.
subject: Articles
  topic: section
subject: geotechnical investigation
  topic: keywords
subject: military training area
  topic: keywords
subject: geophysical study
  topic: keywords
subject: soil stabilization
  topic: keywords
creator: Viktor Sotorník
creator: Petr Černoch
rights: Copyright (c) 2026 Viktor Sotorník, Petr Černoch https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 29
ending page: 31
doi: 10.14311/APP.2026.56.0029

Calibration of the hardening soil model in excalibre
type: item
description: The hardening soil model is one of the most commonly used constitutive models in engineering practice. This model is based on multi-surface plasticity and combines the well-known Mohr-Coulomb failure criterion, a hardening shear surface and a cap yield surface into a single model. The stress-strain behaviour is improved by including nonlinear elasticity. In this paper a calibration tool for a modified version of the hardening soil model is presented which is currently implemented in the online calibration application called ExCalibre.
subject: Articles
  topic: section
subject: hardening soil model
  topic: keywords
subject: calibration
  topic: keywords
subject: ExCalibre
  topic: keywords
creator: Do Chinh Phuong
creator: Tomáš Kadlíček
creator: David Mašín
creator: Jan Najser
rights: Copyright (c) 2026 Do Chinh Phuong, Tomáš Kadlíček, David Mašín, Jan Najser https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 23
ending page: 28
doi: 10.14311/APP.2026.56.0023

Innovative approaches to a solution for surface deformations on earth structures of linear traffic construction
type: item
description: The modification of the slopes of linear transport structures includes humus and grassing which is intended to improve their resistance to erosion. Nevertheless, these slopes are increasingly affected by landslides of the surface layers with the key factors being extreme precipitation fluctuations and the influence of new earthwork technologies. The solution requires an interdisciplinary approach and the introduction of innovative measures. An important role is also played by geodetic monitoring and outputs from modern methods (3D scanning) which provide detailed data on slope changes. A pilot project focused on embankment monitoring in the Hradec Králové region showed the importance of these technologies in dealing with landslides.
subject: Articles
  topic: section
subject: laser scanning
  topic: keywords
subject: slope stability
  topic: keywords
subject: risk management
  topic: keywords
subject: maintenance
  topic: keywords
creator: Václav Mráz
creator: Jiří Vacek
creator: Pavel Dvořák
rights: Copyright (c) 2026 Václav Mráz, Jiří Vacek, Pavel Dvořák https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
starting page: 8
ending page: 15
doi: 10.14311/APP.2026.56.0008

51st and 52nd Conference Foundation Engineering Brno 2023 and 2024
type: item
description: 51st and 52nd CONFERENCE FOUNDATION ENGINEERING BRNO 2023 and 2024 The traditional yearly conference of Foundation Engineering Brno is organized by the Czech Geotechnical Society. This is the largest annual event in the field, where researches, academicians, designers, investors and contractors present, share and discuss the results of their research and share their experiences with each other. Each year is focused on a certain topical subject. Selected experts from abroad are invited for Keynote lecture for each conference. This issue of Acta Polytechnica Proceedings includes selected scientific papers that were presented at the 51st and 52nd Conference of the Foundation Engineering held in Brno in 2023 and 2024. Key Topics: geotechnical investigation, earth structures, foundation structures, underground structures. Date: November 6 - 7, 2023 and November 11 - 12, 2024 Venue: Brno URL: www.cgts.cz Organized by: Czech Geotechnical Society of the Czech Institution of Civil Engineers Guest editor: Alena Zemanová Scientific comittee: 2023 Jiří Barták Jana Frankovská Taťana Holoušová Eva Hrubešová Jan Pruška Daniel Jirásko Jan Masopust Petr Nosek Michael Remeš Jindřich Řičica Ivan Slávik Peter Turček Ivan Vaníček Petr Svoboda Věra Glisníková Jiří Boštík Lumír Miča Lubomír Klímek 2024 Jana Frankovská Ivan Slávik Věra Glisníková Petr Svoboda Tereza Hamouzová Peter Turček Eva Hrubešová Jaroslav Beňo Lubomír Klímek Lumír Miča Daniel Jirásko Taťana Holoušová Ivan Vaníček Martin Vaníček Jan Pruška Alena Zemanová Michael Remeš Local organizing comittee: 2023 Petr Svoboda Věra Glisníková Jiří Boštík Lumír Miča Lubomír Klímek 2024 Daniel Jirásko Taťana Holoušová Ivan Vaníček Martin Vaníček Jan Pruška Alena Zemanová Michael Remeš Guarantor of the peer review proces: Daniel Jirásko Guarantor of language editing: Renáta Nivenová
subject: Foreword
  topic: section
rights: Copyright (c) 2026 https://creativecommons.org/licenses/by/4.0
date: 2026-02-20
publication date: 2026-02-20
doi: 10.14311/

Thermal diffusivity of ATF cladding materials using laser flash technique
type: item
description: Accident tolerant fuel (ATF) cladding materials are designed to improve the fuel behavior in normal operation while further enhancing the material performance in accidental scenarios. The paper presents experimental data on thermal diffusivity for five advanced cladding candidates considered as ATFs, evaluated over a wide temperature range using the laser flash technique. The measured data were evaluated to identify trends in thermophysical behavior in the investigated temperature range. Based on the results, correlations were established to describe the temperature dependence of thermal diffusivity for each material. The analysis also revealed characteristic differences in the thermal diffusivity for various candidates. These findings provide a comparative perspective on the heat transfer capabilities of the tested materials and offer a fundamental experimental basis for their further optimization in accident tolerant fuel applications.
subject: Articles
  topic: section
subject: accident tolerant fuel
  topic: keywords
subject: cladding
  topic: keywords
subject: laser flash technique
  topic: keywords
subject: thermal diffusivity
  topic: keywords
subject: SiC
  topic: keywords
subject: FeCrAl
  topic: keywords
creator: Jakub Vrzal
creator: Martin Ševeček
creator: Luka Vlahovic
rights: Copyright (c) 2025 Jakub Vrzal, Martin Ševeček, Luka Vlahovic https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 89
ending page: 100
doi: 10.14311/APP.2025.55.0089

Experimental study of the Leidenfrost effect in the context of high heat flux cooling
type: item
description: The behavior of water droplet on heated surfaces is experimentally observed to investigate the properties of the insulating vapor layer, a key element of the boiling crisis phenomenon. The lifetime of droplets on the heated surface is measured and compared with analytical models to examine the formation of the insulating vapor layer thickness between the coolant and the heated wall. The potential for reducing the Leidenfrost effect and increasing the critical heat flux by adjusting the surface roughness is examined to improve the thermohydraulic properties of the first-wall cooling channels. The behavior of water droplets on the heated surface with variable roughness is observed through the acoustic emission method. The behavior of water droplets on heated copper surfaces was experimentally studied using inductive and electrical heating with thermocouple temperature control, camera recording and acoustic emission analysis. The measured droplet lifetimes were compared with analytical models to evaluate the insulating vapor layer thickness. The practical relevance lies in reducing the Leidenfrost effect and increasing the critical heat flux, which can improve the cooling performance of high heat flux components such as tokamak first-wall channels.
subject: Articles
  topic: section
subject: Leidenfrost effect
  topic: keywords
subject: water droplet
  topic: keywords
subject: evaporation
  topic: keywords
subject: high heat flux cooling
  topic: keywords
subject: boiling crisis
  topic: keywords
subject: acoustic emission
  topic: keywords
creator: Vojtěch Smolík
creator: Slavomír Entler
creator: Pavel Zácha
creator: Jan Podaný
creator: Alžbeta Endrychová
creator: Marek Nejman
rights: Copyright (c) 2025 Vojtěch Smolík, Slavomír Entler, Pavel Zácha, Jan Podaný, Alžbeta Endrychová, Marek Nejman https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 63
ending page: 70
doi: 10.14311/APP.2025.55.0063

Adaptation of SUBCAL subchannel code for square-lattice rod bundles using PSBT benchmark
type: item
description: Subchannel analysis is a commonly used approach for simulating heat transfer and coolant flow in nuclear reactor cores. This paper presents the adaptation of the SUBCAL computational code, originally developed for reactors with a triangular lattice, to configurations with a square lattice. Geometry-dependent computational relations, models and correlations were identified and analyzed based on the research. The selected relations for the square lattice were implemented into the SUBCAL code, and the computational model was optimized for the recalculation of the PSBT benchmark. Verification of the proposed changes was carried out by evaluating the results of the benchmark recalculation against experimental data and through code-to-code comparisons with results from other participating organizations. These modifications and the recalculated PSBT benchmark represent the starting point for validating the SUBCAL code for this type of analysis.
subject: Articles
  topic: section
subject: subchannel analysis
  topic: keywords
subject: SUBCAL
  topic: keywords
subject: PSBT benchmark
  topic: keywords
subject: boiling crisis
  topic: keywords
subject: void fraction
  topic: keywords
creator: Lucie Titzová
creator: Vojtěch Caha
creator: Jiří Čížek
rights: Copyright (c) 2025 Lucie Titzová, Vojtěch Caha, Jiří Čížek https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 80
ending page: 88
doi: 10.14311/APP.2025.55.0080

Dispersion type metal-metal based high-density fuels for nuclear reactors – sample preparation, analysis and examination of LOCA behaviour
type: item
description: Metal-based nulear fuels have been proposed as an alternative to UO2 partly in response to increasing pressure to continually improve nuclear system safety. In this work, a set of High-Density Fuel samples manufactured from depleted uranium alloys and Zr-based matrix have been manufactured and evaluated in the as-manufactured and post-LOCA conditions. A qualitative analysis of the samples showed that the matrix and fuel behaviour is mostly consistent with theory and available research while quantitative analysis revealed a major impact of fuel element geometry on packing density and distribution. Fuel–matrix–cladding interactions of varying intensity have also been observed during fabrication and under LOCA conditions.
subject: Articles
  topic: section
subject: Accident Tolerant Fuel
  topic: keywords
subject: High-Density Fuel
  topic: keywords
subject: nuclear fuel
  topic: keywords
subject: dispersion fuel
  topic: keywords
subject: metallic uranium
  topic: keywords
creator: Petr Šárek
creator: Jakub Krejčí
creator: Tomáš Chmela
creator: Jitka Kabátová
rights: Copyright (c) 2025 Petr Šárek, Jakub Krejčí, Tomáš Chmela, Jitka Kabátová https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 71
ending page: 79
doi: 10.14311/APP.2025.55.0071

Numerical simulation of secondary heat exchanger in S-Allegro
type: item
description: This paper presents a computational analysis of the Secondary Heat Exchanger (SHX) in the S-Allegro experimental facility. The S-Allegro facility is a helium circuit which serves as an experimental platform for validating thermohydraulic calculations of helium flow in support of Gascooled Fast Reactor (GFR) development. A computational analysis performed on the SHX included calculations using criterial equations of heat transfer and, most importantly, numerical simulation. Both methods were compared to experimental data and adjusted to achieve a good agreement. The results of the numerical simulations are used to analyse flows in the heat exchanger and identify potential improvements in future design of heat exchangers for GFR. The study provides insights into the thermal performance of helium-water heat exchangers and contributes to the validation of computational methods for GFR technology development.
subject: Articles
  topic: section
subject: CFD
  topic: keywords
subject: GFR
  topic: keywords
subject: Gas-cooled Fast Reactor
  topic: keywords
subject: heat exchanger
  topic: keywords
subject: nuclear power
  topic: keywords
subject: numerical simulations
  topic: keywords
creator: Adam Palouda
rights: Copyright (c) 2025 Adam Palouda https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 56
ending page: 62
doi: 10.14311/APP.2025.55.0056

Subtractive gamma discrimination technique for neutron diamond detectors operating in mixed radiation fields
type: item
description: A detection system based on diamond detectors and subtractive discrimination was developed for the measurement of thermal neutrons flux distribution changes during rod drop transient at the VR-1 reactor. The detection system was modified to replace the pulse-shaped method used for discrimination. The electronics available at the department was not able to measure high count rates with the pulse shape discrimination method. Subtractive discrimination allows us to reduce the requirements in the signal processing area, as the shape does not need to be recorded, and therefore the digitizer performance can be significantly lower. For this reason, a pulse stretching amplifier was developed and tested.
subject: Articles
  topic: section
subject: neutron detection
  topic: keywords
subject: amplifier
  topic: keywords
subject: subtractive gamma discrimination
  topic: keywords
subject: diamond detectors
  topic: keywords
subject: nuclear reactor
  topic: keywords
subject: transients
  topic: keywords
creator: Ondřej Novák
creator: Ondřej Huml
creator: Martin Kropík
creator: Ľubomir Sklenka
rights: Copyright (c) 2025 Ondřej Novák, Ondřej Huml, Martin Kropík, Ľubomir Sklenka https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 49
ending page: 55
doi: 10.14311/APP.2025.55.0049

Microstructural and mechanical property characterization of high-density uranium fuel for light-water reactors
type: item
description: One of the key concepts in the development of accident-tolerant fuels (ATFs) involves the use of high-density fuels, aimed at improving the safety and economics of light-water reactors. This work focuses on the microstructural and mechanical characterization of experimentally fabricated segments of dispersion-type high-density uranium fuels with a zirconium matrix and Zr-based cladding, intended for future testing in research reactors. Both U-Mo alloys and pure uranium metal were investigated, with particular attention given to the influence of thermal treatment on the phase composition and microstructure of the fuel segments. In addition, changes resulting from thermal exposure were evaluated. The research includes the identification of newly formed phases during transient conditions and the analysis of diffusion phenomena in the material. Mechanical properties were evaluated through microhardness measurements, and the results will serve as input parameters for computational simulations using the Serpent code to support the introduction of these fuels in the VR-2 research reactor.
subject: Articles
  topic: section
subject: accident tolerant fuels
  topic: keywords
subject: high-density uranium fuels
  topic: keywords
subject: microstructure
  topic: keywords
subject: research reactor
  topic: keywords
subject: U-Mo
  topic: keywords
creator: Filip Mach
creator: Patricie Halodová
creator: Martin Ševeček
creator: Jakub Krejčí
creator: Petr Šárek
rights: Copyright (c) 2025 Filip Mach, Patricie Halodová, Martin Ševeček, Jakub Krejčí, Petr Šárek https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 41
ending page: 48
doi: 10.14311/APP.2025.55.0041

Project VALVERDE – validation and verification of computational tools to describe corium spill to improve deterministic analyses of severe accidents
type: item
description: The VALVERDE project focuses on the investigation of the melt flow characteristics of the core melt simulant material and the subsequent development of suitable procedures and methodologies for the description of the melt flow of the simulant in a defined geometry. The main aim is to develop an experimental setup in which the melt spreading of the corium will be performed using suitable simulants. The current version of the experimental setup and the CFD simulations of the spreading of the reactor core melt simulant will be presented.
subject: Articles
  topic: section
subject: corium
  topic: keywords
subject: melt spreading
  topic: keywords
subject: corium simulant
  topic: keywords
subject: CFD
  topic: keywords
creator: Jan Komrska
creator: Pavel Pekárek
creator: Tomáš Hoppe
creator: Pavel Zácha
rights: Copyright (c) 2025 Jan Komrska, Pavel Pekárek, Tomáš Hoppe, Pavel Zácha https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 33
ending page: 40
doi: 10.14311/APP.2025.55.0033

Impact of fecral oxide composition on severe accident progression in MELCOR
type: item
description: Experimental studies have shown that the composition of the oxide layer forming on FeCrAl surface depends strongly on the temperature of the environment, with varying fractions of aluminum, chromium, and iron oxides forming under different conditions. In this work, multiple oxide compositions were incorporated into MELCOR simulations for evaluation of their impact on cladding degradation. The weight fractions of aluminum, chromium, and iron oxides were derived from published experimental data, serving as basis for modifications of the material model. Simulations of a representative Loss of Coolant Accident scenario show that these changes significantly affect cladding temperature evolution, oxidation progression, and hydrogen generation. These results highlight the need to account for environmentally dependent behavior when modeling advanced cladding materials in integral codes.
subject: Articles
  topic: section
subject: ATF cladding
  topic: keywords
subject: FeCrAl
  topic: keywords
subject: LOCA
  topic: keywords
subject: severe accident
  topic: keywords
subject: MELCOR
  topic: keywords
creator: Lukáš Hamřík
creator: Peter Mičian
creator: Štěpán Foral
creator: Karel Katovský
creator: Pavel Máca
creator: Jitka Vojáčková
rights: Copyright (c) 2025 Lukáš Hamřík, Peter Mičian, Štěpán Foral, Karel Katovský, Pavel Máca, Jitka Vojáčková https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 25
ending page: 32
doi: 10.14311/APP.2025.55.0025

High-temperature oxidation of non-zirconium materials for ATF
type: item
description: Non-zirconium materials, such as silicon carbide (SiC) and FeCrAl alloys, have attracted interest for developing Accident-Tolerant Fuel (ATF) cladding systems owing to their superior hightemperature oxidation resistance. SiC offers excellent thermal stability, high-temperature properties, irradiation tolerance, and low activation, while FeCrAl alloys provide outstanding oxidation resistance in steam and air through a stable alumina (Al2O3) layer. This study examines their oxidation behavior under simulated severe-accident conditions. Microstructural changes and mechanical integrity after exposure were analyzed using scanning electron microscopy (SEM) and ring compression tests (RCT). The analysis revealed material-specific strengths and limitations, emphasizing the role of temperature and oxidation environment.
subject: Articles
  topic: section
subject: oxidation
  topic: keywords
subject: Accident-Tolerant Fuel (ATF)
  topic: keywords
subject: Silicon-Carbide (SiC)
  topic: keywords
subject: FeCrAl
  topic: keywords
creator: Alžběta Endrychová
creator: Jakub Krejčí
creator: Martin Ševeček
creator: Martin Cesnek
creator: Claudia Aparicio
creator: David Rada
rights: Copyright (c) 2025 Alžběta Endrychová, Jakub Krejčí, Martin Ševeček, Martin Cesnek, Claudia Aparicio, David Rada https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 16
ending page: 24
doi: 10.14311/APP.2025.55.0016

Corrosion behaviour of AISI 348 stainless steel in simulated WWER environment and during LOCA conditions
type: item
description: This study investigates the corrosion and high-temperature oxidation behaviour of AISI 348 stainless steel under normal and extreme conditions for potential nuclear applications. Plate specimens were exposed to simulated WWER primary water conditions in an autoclave at 360 °C for extended duration, reaching up to 1659 days. In addition to long-term exposure testing, short-term high-temperature oxidation experiments were performed at temperatures up to 1 400 °C to evaluate oxide scale formation, spallation behaviour, and structural integrity. Characterization techniques included Mössbauer spectroscopy for oxide phase identification, microhardness measurements, and optical microscopy for grain size evaluation. Mechanical testing, including ductility assessment and microhardness measurements, was conducted after high-temperature exposure to evaluate the material’s ability to retain mechanical integrity under accidental conditions.
subject: Articles
  topic: section
subject: AISI 348
  topic: keywords
subject: stainless steel
  topic: keywords
subject: corrosion
  topic: keywords
subject: LOCA conditions
  topic: keywords
subject: WWER
  topic: keywords
creator: Václav Bouček
creator: Jakub Krejčí
creator: Martin Cesnek
creator: Jitka Kabátová
creator: Martin Ševeček
rights: Copyright (c) 2025 Václav Bouček, Jakub Krejčí, Martin Cesnek, Jitka Kabátová, Martin Ševeček https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 8
ending page: 15
doi: 10.14311/APP.2025.55.0008

Post-CHF nuclear fuel operation with Time-at-Temperature criteria
type: item
description: The dryout and departure from nucleate boiling criteria are used to set safety limits on nuclear heat transfer and temperature values in nuclear reactors. This review argues for the use of a Time-at-Temperature criterion to improve efficiency and utilization of nuclear fuels and reduce costs. To illustrate the importance of such criteria, the review presents the different phenomena of cladding and fuel rods that could impact the continued operation of nuclear reactors, as well as the experiments and operating events that occurred in light-water reactors.
subject: Articles
  topic: section
subject: Time at Temperature
  topic: keywords
subject: Critical Heat Flux
  topic: keywords
subject: Departure from Nucleate Boiling
  topic: keywords
subject: dryout
  topic: keywords
subject: nuclear fuel
  topic: keywords
creator: Ambre Bertoux
creator: Martin Ševeček
rights: Copyright (c) 2025 Ambre Bertoux, Martin Ševeček https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29
starting page: 1
ending page: 7
doi: 10.14311/APP.2025.55.0001

Šimáně 2025 – International Student Conference on Nuclear Engineering
type: item
description: Nuclear-related sciences and technology have a long and rich history within the Czechoslovakia. Even though the Czech Republic and Slovakia have been separated since 1993, wide cooperation on different levels including education and research still exists. In order to support cooperation and good relations between Czech and Slovak students in nuclear engineering and related disciplines, the Department of Nuclear Reactors organizes annually a student conference on nuclear engineering - Šimáně. Students mainly from Czech and Slovakian nuclear institutes are invited to present their research and share their knowledge. Participants from other foreign institutes are welcomed as well. The conference is named after professor Šimáně, who graduated at the Dr. Edvard Beneš Technical University in Brno. During his early career, he had the opportunity to work with Fréderic Joliot-Curie at College de France. Later, he significantly contributed to the foundation of the nuclear science, industry and education in the Czechoslovakia. He became the first employee of the Institute of Nuclear Physics at the Czechoslovakian Academy of Science, later he became the first director of the Nuclear Research Institute in Řež. Professor Šimáně was well established even on the international level. He was a director at the Joint Institute of Nuclear Research in Dubna or a division director at the International Agency for Atomic Energy. His work was also significantly connected with Faculty of Nuclear Sciences, CTU in Prague where he acted as Dean from 1967 to 1972. The main objective of the conference is to provide an opportunity for BSc., MSc. and Ph.D. students of nuclear-oriented study programmes to publish and present their scientific results achieved during their university studies. Furthermore, it should give the participants experience in the field of presenting their own research, writing scientific papers and also broaden their knowledge throughout the related fields and to remind them ri…
subject: Foreword
  topic: section
subject: Neutron-physical calculations, Material research and application of ionizing radiation, Thermal-physical calculations and accident simulations
  topic: keywords
creator: Editorial Foreword
rights: Copyright (c) 2025 Editorial Foreword https://creativecommons.org/licenses/by/4.0
date: 2025-12-29
publication date: 2025-12-29

Experimental analysis of physical properties of lightweight gypsum plasterboard
type: item
description: This article presents an experimental analysis of a newly developed gypsum plasterboard for dry construction. The new board has a density that is 40 kgm−3 lower than existing boards and was created with an emphasis on conserving resources and reducing the energy consumption required for its production. Because gypsum is the most energy-intensive raw material, the research team focused on minimizing its content. As a result, the new board uses 12 % of mass less gypsum, which translates into an approximately 6 % reduction in CO2 emissions from the annual production process. Crucially, this was achieved while meeting the relevant standard requirements for mechanical, thermal-technical, and fire performance, and maintaining the board’s “sustainable” user properties. The article details the experimental analysis conducted on key mechanical and thermal-technical parameters of the board.
subject: Articles
  topic: section
subject: gypsum plasterboard
  topic: keywords
subject: lightweight
  topic: keywords
subject: mechanical properties
  topic: keywords
subject: experiments
  topic: keywords
creator: Martin Hataj
creator: Jan Jochman
creator: Jan Pošta
creator: Mária Domonkos
creator: Ondřej Zobal
creator: Miroslav Nyč
rights: Copyright (c) 2025 Martin Hataj, Jan Jochman, Jan Pošta, Mária Domonkos, Ondřej Zobal, Miroslav Nyč https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 29
ending page: 33
doi: 10.14311/APP.2025.54.0029

A study of the behavior of samples of high-performance concrete shells with filled core exposed to compression
type: item
description: The production of concrete has a huge impact on the environment, especially due to its emission of CO2. Nowadays, it is required to reduce CO2 emissions and at the same time reduce the consumption of non-renewable resources. One way to achieve these goals is through the usage of recycled aggregate. However, when these materials are used, there are significant changes in the properties of concrete, particularly a reduction of mechanical strength, modulus of elasticity, and durability. This article presents the possibility of using a thin shell made of high-performance concrete as core protection of a concrete sample with recycled aggregate to improve the abovementioned properties. Moreover, using high-performance concrete as the outer layer enables the potential of high-performance concrete to be exploited. The article describes the influence of different shell reinforcements on the failure of the samples under compressive stress. A shell layer without additional reinforcement was used for the reference samples. Other sets of samples contained dispersed reinforcement in the form of polypropylene or polyvinyl alcohol fibers. The last reinforcement was a technical textile – a laboratory-prepared composite grid made of carbon rovings. All samples were subjected to a compressive test and the failure mode of the samples was observed in particular.
subject: Articles
  topic: section
subject: fiber-reinforced concrete
  topic: keywords
subject: textile-reinforced concrete
  topic: keywords
subject: high-performance concrete
  topic: keywords
subject: concrete with recycled aggregate
  topic: keywords
subject: fiber reinforcement
  topic: keywords
subject: textile reinforcement
  topic: keywords
subject: carbon footprint
  topic: keywords
creator: Eliška Kafková
creator: Jan Macháček
creator: Věra Kabíčková
creator: Tomáš Vlach
rights: Copyright (c) 2025 Eliška Kafková, Jan Macháček, Věra Kabíčková, Tomáš Vlach https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 50
ending page: 54
doi: 10.14311/APP.2025.54.0050

Deep learning-based modeling and simulation of heat conduction
type: item
description: The present study focuses on applying deep neural networks (DNNs) to surrogate modeling of heat conduction problems. Deep learning algorithms, valued for their ability to learn hierarchical data representations through multi-layered networks, excel at identifying complex patterns. In this work, the U-Net architecture – widely recognized for its effectiveness in image segmentation – is adapted to model stationary heat transfer, providing a novel approach to a critical challenge in engineering and physics. Specifically, we propose a deep learning-based surrogate model to predict stationary temperature fields in 2D rectangular domains representing two-phase heterogeneous materials.
subject: Articles
  topic: section
subject: stationary heat transport
  topic: keywords
subject: convolutional neural network
  topic: keywords
subject: U-Net architecture
  topic: keywords
creator: Ondřej Šperl
creator: Jan Sýkora
rights: Copyright (c) 2025 Ondřej Šperl, Jan Sýkora https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 79
ending page: 84
doi: 10.14311/APP.2025.54.0079

Characterization of the microstructure of cement paste exposed to gamma radiation by scanning electron microscopy
type: item
description: Hardened cement paste with a water-cement ratio of 0.4 was examined under five different relative humidity (RH) conditions (11 %, 33 %, 76 %, 96 %, and 100 %). These samples were exposed to gamma radiation with a total dose of 13.82 MGy over 341 days. Scanning electron microscopy (SEM) was the primary tool used for characterizing the samples’ microstructure at a microscale, aided by image analysis (IA), which showed negligible changes in Calcium-Silicate-Hydrate phases but a decrease in Portlandite of 1.5–3.5 % under 33–100 % RH conditions. Point elemental analysis was conducted to determine the (Ca-S)/Si ratio of the inner product, finding a significant increase of up to 20 % at medium RH conditions (33–76 %).
subject: Articles
  topic: section
subject: electron microscopy
  topic: keywords
subject: cement paste
  topic: keywords
subject: gamma radiation
  topic: keywords
creator: Andrea Špaková
creator: Jiří Němeček
creator: Lukáš Procházka
creator: Patricie Halodová
rights: Copyright (c) 2025 Andrea Špaková, Jiří Němeček, Lukáš Procházka, Patricie Halodová, Jiří Němeček https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 72
ending page: 78
doi: 10.14311/APP.2025.54.0072

Mechanical properties of cement composites with plasma-treated waste glass aggregate
type: item
description: This research focuses on evaluating the effect of low-temperature plasma surface treatment of finely ground recycled glass on the mechanical properties of cement composites. The use of waste glass in construction represents an environmentally friendly alternative, but its application may cause alkalisilica reaction (ASR), leading to material degradation. To prevent this phenomenon, plasma treatment was applied with the aim of improving the adhesion of glass particles to the cement matrix, enabling the partial replacement of traditional filler materials. In cement composites, glass primarily functions as an alternative fine aggregate. Its use offers several potential advantages, including improving the pozzolanic properties of the composite, meaning it reacts with calcium hydroxide, thereby contributing to the formation of additional binding phases. In this way, glass not only replaces traditional fillers but also enhances the long-term mechanical properties of the material. However, inappropriate particle size or high reactivity of the glass may lead to ASR, which causes cracking and degradation of the material. Plasma treatment was employed to mitigate these negative effects by enhancing the adhesion between glass particles and the cement matrix, thereby increasing the overall cohesion, strength, and resistance of the composite to environmental influences and degradation. The samples were tested for compressive strength and bulk density after 28, and 168 days of curing. The results indicated that plasma treatment, particularly with oxygen, led to a moderate improvement in mechanical properties compared to untreated samples, but the values did not reach the levels observed in the reference sample without glass powder.
subject: Articles
  topic: section
subject: waste glass
  topic: keywords
subject: cold plasma
  topic: keywords
subject: surface treatment
  topic: keywords
subject: mechanical properties
  topic: keywords
subject: cement composite
  topic: keywords
creator: Aleš Palička
creator: Zdeněk Prošek
creator: Pavel Tesárek
creator: Oleg Babčenko
rights: Copyright (c) 2025 Aleš Palička, Zdeněk Prošek, Pavel Tesárek, Oleg Babčenko https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 62
ending page: 66
doi: 10.14311/APP.2025.54.0062

Prestress load distribution modeling for containment digital twin model
type: item
description: This paper examines the prestress load distribution in the ducts of the prestressing tendons of a VVER-type nuclear reactor containment. It introduces a method for distributing the simplified linear load from the prestressing cable onto the surface area of the duct. Furthermore, a procedure for applying this calculation to a detailed numerical 3D model of a containment segment is described. This method can be implemented into computational software, such as OOFEM, to incorporate this more accurately defined load into a comprehensive stress analysis of the segment. Realistic definition of load distribution from prestressing tendons on the surface of the ducts is critical for identifying potential deviations from a uniform prestress distribution within the containment wall. This, in turn, facilitates assessments such as evaluating the extension of the structure’s service life.
subject: Articles
  topic: section
subject: unbonded prestressing reinforcement
  topic: keywords
subject: structural loading
  topic: keywords
subject: prestressing ducts
  topic: keywords
subject: digital twin
  topic: keywords
subject: 3D model
  topic: keywords
creator: Matyáš Ratislav
creator: Bořek Patzák
creator: Petr Štemberk
creator: Jan Štěpán
rights: Copyright (c) 2025 Matyáš Ratislav, Bořek Patzák, Petr Štemberk, Jan Štěpán https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 67
ending page: 71
doi: 10.14311/APP.2025.54.0067

Prestressed textile reinforced concrete with carbon composite reinforcement
type: item
description: The article deals with the potential of prestressed textile concrete. The prestressing principle, which is nowadays commonly used part of construction, is combined with the developing technology of textile concrete which is concrete reinforced with non-metallic reinforcement. In this case the carbon reinforcement is used because it shows the best mechanical parameters in comparison with glass or basalt reinforcement. The paper presents the advantages of using prestressed textile carbon composite reinforcement of textile reinforced concrete and at the same time deals with problems related to it, such as the correct choice of impregnation using epoxy resin and the technological method of introducing prestress into the sample. The article focuses on comparison between 3 types of epoxy resin, specifically Sikafloor 156, LH 300 and EPOREZIT EPOVILL-A. The results are presented on experimental samples tested in four-point bending test.
subject: Articles
  topic: section
subject: HPC
  topic: keywords
subject: textile reinforcement
  topic: keywords
subject: prestressed concrete
  topic: keywords
subject: prestressing form
  topic: keywords
subject: epoxy resin
  topic: keywords
creator: Jan Macháček
creator: Eliška Kafková
creator: Věra Kabíčková
creator: Tomáš Blažek
creator: Tomáš Vlach
rights: Copyright (c) 2025 Jan Macháček, Eliška Kafková, Věra Kabíčková, Tomáš Blažek, Tomáš Vlach https://creativecommons.org/licenses/by/4.0
date: 2025-12-15
publication date: 2025-12-15
starting page: 55
ending page: 61
doi: 10.14311/APP.2025.54.0055