Projects / Programmes
January 1, 2020
- December 31, 2027
| Code |
Science |
Field |
Subfield |
| 2.13.00 |
Engineering sciences and technologies |
Process engineering |
|
| 2.03.00 |
Engineering sciences and technologies |
Energy engineering |
|
| Code |
Science |
Field |
| T160 |
Technological sciences |
Nuclear engineering and technology |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
Nuclear safety, nuclear power plant, fluid mechanics, heat transfer, mass transfer, system code, computational fluid dynamics, steam explosions, combustion, pool scrubbing, structural integrity, solid mechanics, probability, risk, interdisciplinary, High performance computing.
Data for the last 5 years (citations for the last 10 years) on
April 26, 2024;
A3 for period
2018-2022
| Database |
Linked records |
Citations |
Pure citations |
Average pure citations |
| WoS |
402 |
4,687 |
3,969 |
9.87 |
| Scopus |
517 |
6,116 |
5,159 |
9.98 |
Researchers (25)
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0106 |
Jožef Stefan Institute |
Ljubljana |
5051606000 |
90,753 |
Abstract
The program consists of four major interrelated topics that cover a large part of reactor engineering.
HEAT AND MASS TRANSFER
Basic heat and mass transfer phenomena are being investigated theoretically and experimentally. Single-phase turbulent heat transfer is modelled with Direct Numerical Simulation and Large Eddy Simulation. Two-phase gas-liquid flow is modelled by coupling interface tracking/sharpening and two-fluid models. Velocity and temperature experimental measurements in momentum and thermal boundary layers will be performed, as well as measurements describing interface behaviour in two-phase flow.
Heat and mass transfer in reactor systems is being investigated using descriptions on different length scales. Thermal-hydraulic transients in pressurized water reactors will be simulated using system codes (volume-averaged scale) and Computational Fluid Dynamics codes (local scale), including coupling of thermal-hydraulic and reactor physics models. Phenomena in advanced liquid metal and gas-cooled reactors will also be simulated. Fluid-structure interaction will be studied by coupling thermal hydraulics and structural response.
SEVERE ACCIDENT PHENOMENA
The topic comprises fuel-coolant interaction, behaviour of nuclear power plant (NPP) containment atmosphere, and pool scrubbing. Studies of fuel-coolant interaction will involve stratified steam explosions in water and processes of fuel-sodium interaction, including melt fragmentation. The behaviour of NPP containment atmosphere containing hydrogen will be modelled on the local instantaneous scale; scaling-up of experimental results to actual NPPs will be proposed. Pool scrubbing of gas, contaminated by fission products in the form of particles, will be investigated using multi-fluid modelling.
STRUCTURAL INTEGRITY AND AGEING
Principles and mechanisms of cracking in reactor systems, due to the specifics of NPP operation, will be investigated.
A tool for classifying metallic polycrystalline aggregates according to their susceptibility to intergranular cracking will be developed.
Engineering-like and physics-based computational tools will be developed to study the influence of localized plastic deformation on intergranular cracking in neutron-irradiated austenitic stainless steels.
A tool for assessing the uncertainty of microstructural fatigue cracks, due to high-cycle complex loads in reactor systems, will be developed.
PROBABILISTIC SAFETY ASSESSMENT (PSA)
PSA is a systematic probabilistic method applied for analysis of reliability and safety of complex systems. New methods that will contribute to improved risk modelling of NPPs will be developed.
Deterministic and probabilistic safety analyses will be integrated and used for risk-informed decision making.
A new method for assessment of onsite power system reliability of a NPP and consequential implications on plant safety will be developed.
New importance measures for identification of most important elements of a NPP will be introduced.
Significance for science
The program consists of four major interrelated topics that cover a large part of reactor engineering.
HEAT AND MASS TRANSFER
1. Basic heat and mass transfer phenomena
Experiments, Direct Numerical Simulation and Large Eddy Simulation results of mixed convection, single-phase heat transfer in various simplified geometries can elucidate physical phenomena on the smallest length scales. The created databases can be used for further development of Reynolds Averaged Navier-Stokes turbulent models for less computationally demanding simulations in realistic geometries.
Direct Numerical Simulation of two-phase gas-liquid flow resolves most of the spatial and temporal scales and can explain some of the basic two-phase flow phenomena. Two-phase flow models, which are based on the two-fluid model and are able to perform tracking of large interfaces and neglect small ones, will require assessment and further improvement of (semi)empirical closures in various flow regimes. Improved mathematical models and numerical schemes will improve the capabilities of three-dimensional codes for simulations of realistic two-phase flows.
High-quality experiments in simple geometries, which will be performed in our experimental loop, will help to explain basic phenomena of turbulent heat and mass transfer, as well as of gas-liquid interface behaviour.
2. Heat and mass transfer in reactor systems
Simulations of complex turbulent flows in fuel bundles with mixing vanes and the development of three-dimensional description of the flow in the reactor vessel and in primary coolant loops will provide similar contributions as the research within basic heat and mass transfer phenomena.
Complete sets of systems in NPPs are described with system-like codes, which combine one-dimensional (1D) description of cooling loops with a quasi-3D description of the reactor vessel. The current research aims at developing methods for integrating deterministic and probabilistic safety assessment of NPPs. An additional challenge is the quantification of uncertainties of both kinds of safety analyses.
SEVERE ACCIDENT PHENOMENA
One of the important remaining issues in interaction of two liquids with high temperature difference, of which one may reach saturation conditions during the interaction, is the likelihood and consequences of energetic and non-energetic fuel-coolant interactions. The unexpected strong spontaneous steam explosions in stratified melt-water configurations were observed only recently, and research will contribute to the improved understanding of this phenomenon. Research on melt fragmentation and potential of vapour explosions in sodium will contribute to the understanding of basic fuel-sodium interaction phenomena.
The investigation of the behaviour of a non-homogeneous atmosphere in nuclear power plant containment will contribute to the advancement of knowledge in the specific topic of mixing and entrainment in a multi-component gaseous mixture. It will also contribute new knowledge on modelling of turbulence in gas mixing.
The investigation of pool scrubbing of gas, contaminated with fission products in the form of particles, will contribute new knowledge on three-phase gas-liquid-solid particles hydrodynamics.
STRUCTURAL INTEGRITY AND AGEING
The research on ageing processes of metals will contribute in the areas of development and improvement of modelling approaches. Specifically, the statistical analysis of intergranular stresses performed in a large set of polycrystalline models will identify most influential material, morphological and loading parameters that contribute to stress concentrations, which will result in a more detailed understanding of crack initiation phenomena. Also, practical computational tools will be developed that will be useful in further research.
PROBABILISTIC SAFETY ASSESSMENT
Probabilistic safety assessment must evolve in order to address existing and future challenges with the consider
Significance for the country
The results of proposed aspects, four fields of research and their mutual interrelation and complementarity embody a necessary theoretical basis for safety analyses, related with the safe and stable operation of the Krško (Slovenia) nuclear power plant (NPP), as well as for the execution of the most demanding expert tasks for the Krško NPP and the Slovenian Nuclear Safety Administration.
In more detail: research in the field of thermal-hydraulic safety analyses, including combi-ned research with structural and probabilistic safety analyses, are especially important for interdisciplinary analyses and expert tasks that involve transient phenomena and hypothetical accidents. In this way, the research contributes to the long-term availability of competitive electrical energy, and to the protection of the population and the environment. The long-term operation of the Krško NPP also means large reductions of greenhouse gas emissions.
Additional research in the field of structural safety analyses enables a more accurate prediction of the lifetime of important components of the Krško NPP, which has a direct influence on the availability of electricity. At the same time, the purposes of the research are set to enable direct knowledge transfer in support of the life-time extension of the existing plant and the planned construction of the new nuclear plant in Slovenia. The acquired knowledge will also be useful in the process and mechanical industries.
The high level of nuclear safety puts nuclear energy among the safest energy sources on the planet. Individual and societal health risks due to the release of radioactive materials are extremely low. Nevertheless, a significant part of the population sees nuclear energy as excessively dangerous. Our research and public activities of our members help to reduce the gap between the perceived risk and actual risk of nuclear power plants.
The Reactor engineering research programme forms the basis of the under-graduate and graduate nuclear engineering studies programmes at the Faculty of mathematics and physics of the University of Ljubljana. The programme represents also a basis for international cooperation, which provides access to wider knowledge and contributes to the increase of the national expertise.
