MAIN RESEARCH AREAS OF THE LABORATORY:
– reliability of power plant facilities: research of metal aging processes and degradation of properties due to the impact of operational factors;
– development and research of multifunctional materials and composites;
– testing of materials, assessment and analysis of their qualitative indicators.
RELIABILITY OF POWER PLANT FACILITIES: RESEARCH OF METAL AGING PROCESSES AND DEGRADATION OF PROPERTIES DUE TO THE IMPACT OF OPERATIONAL FACTORS
The Laboratory carries out research aimed at the investigation of ageing processes of steel and special alloys that are used as constructional elements for power plants and at studying patterns of aging processes, solving issues concerning control of these processes and service life. Applying mechanical tests, X-ray Diffraction (XRD) and elemental composition analysis, as well as optic and scanning electron microscopy, structural and property changes of aged steel and non-ferrous alloys are studied. Experimental and numerical methods are used to predict operational reliability taking into account material ageing processes and other operational factors. The implementation of the work focuses on the investigation of fundamental physical and chemical phenomena affecting structure and properties of metals. In this research direction, researchers of the Laboratory participate in long-term institutional scientific research and experimental development programs: Scientific research of safety important processes taking place in nuclear and thermal nuclear facilities and Research of processes of nuclear power plant operation decommissioning, nuclear waste and spent nuclear fuel management and radiation impact analysis
In 2016, the project Service life assessment model for new generation steel funded by the Research Council of Lithuania was completed. The objective of the work was to investigate developments of structural changes in steel under high temperature and their influence on the mechanical characteristics and degradation parameters. The structural changes occurring under the influence of temperature were determined investigating phase transformations in steel by assessing the evolution of steel carbides and changes in crystal lattice parameters. Phase changes of steel at 600-700 °C was investigated by means of XRD, scanning electron microscopy and EDX methods. Due to chemical elements diffusion during steel ageing evolution of carbides occurs which manifests by changes in size, element composition and crystalline lattice parameters. The analysis M23C6 carbide lattice changes during high temperature aging revealed that these changes are characteristic for estimation the extent of steel degradation, and thus may be recommended instead of other structural investigation methods.
Johnson-Mehl-Avrami kinetic equation was applied for creating a kinetic model for predicting changes of carbide crystallographic parameters as well as steel mechanical properties taking into account aging temperature and time. It was determined that predicted tensile and creep properties of thermally aged samples correlate well with experimental data. Research results revealed that the developed method rather well defines changes of mechanical properties at thermal ageing and could be relevant in estimating energy facilities ageing-related degradation and could be applied in forecasting their lifetime evaluation.
Fig. 1. Investigation of martensite ferrite steel ageing processes: identification of carbide changes
The Laboratory continued the research initiated by IAEA in 1998 related to degradation impact of hydrogen and hydrides on zirconium alloys. Analysis of Nuclear fuel Cladding Resistance to Hydride Cracking during Long-Term Storage
coordinated by the International Atomic Energy Agency (IAEA) was completed in 2016. The objective of this work was to develop experimental procedures in order to assess conditions of hydride cracking in zirconium alloy fuel cladding – threshold stress intensity factor values and temperature limits, under which failure of fuel cladding may occur. By applying controlled hydriding, special construction samples were made of zirconium alloy fuel cladding, in which by changing stress levels, hydride cracking process under given temperatures was studied. The research is important for solving the issues of ensuring safe operation of nuclear power plants and assessing the resistance of fuel cladding to the hydride cracking during long-term storage of spent nuclear fuel.
In 2016, researchers of the Laboratory together with the team of the Laboratory of Nuclear Installation Safety continued the European Union financed programme Horizon 2020 project INcreasing Safety in NPPs by Covering gaps in Environmental Fatigue Assessment, INCEFA-PLUS. The objective of the project INCEFA-PLUS is to obtain new experimental data and submit recommendations by evaluating fatigue induced degradation in the nuclear reactor operating conditions. The impact of strain and stress mode, hold time, and the surface roughness on the fatigue life of austenitic steels will be investigated. Information about the possible fatigue degradation mechanisms will be obtained after conducting the microstructure and a fractographic research of the tested samples. The obtained experimental data will be standardized and presented in the online fatigue strength database. The research will seek to fill in the current gaps in the existing data: create fatigue assessment procedures that would as much as possible comply with the real NPP operational conditions. The research will seek to fill in the current gaps in the existing data: create fatigue assessment procedures that would as much as possible comply with the real NPP operational conditions. During the project, a modified environmental fatigue assessment procedures will be created, which will allow a more accurate estimation of the mean strain, hold time and surface roughness influence. This will enable better management of nuclear facility components ensuring a long-term safe operation of the NPP.
Under a contract with JSC „Kauno arena“ “Corrosion failure analysis of galvanized steel hot water supply pipelines and ethylene glycol supply pipelines used in air conditioning system
” samples of steel galvanized pipes, used in hot water plumbing system, were investigated. Analysis of corrosion reasons was carried out, factors evoking it were identified and recommendations were submitted. The samples of ethylene glycol supply piping, used in conditioning system, were investigated and its leakage reasons were identified.DEVELOPMENT AND RESEARCH OF MULTIFUNCTIONAL MATERIALS AND COMPOSITES
In 2016, a subsidy-funded scientific Research of impact of nano-sized modified admixtures on the structure of composite materials was completed. The work aims at investigating the structure of natural and synthetic layered nano silicates and optimizing the modification methodology; it also seeks to research the impact of modified silicates and complex nano-sized admixtures on morphology of cement composite materials.
The influence of modification conditions on the structural changes of nano-sized admixtures (natural and synthetic nano-silicates) was identified, i.e. on the distance among tetrahedral layers, and on the nature of modifier and nano-silicates interaction. Modification methodology of nano-silicate as nano-filler for constructional materials was optimized, it can also be applied in implementing other analogous research and continuing activities in the field of new composites development with the assigned tasks.
The obtained results are an important step in the development of composite material, the components of which will be replaced by alternative and environmentally friendly materials, yet the structural properties of the material would remain unchanged. IDENTIFICATION OF PLASTICS
The European Commission sets a target by the 2025 to reduce pollution related with plastics industry and to increase recycling of plastics waste and secondary usage in EU member states. The problem is relevant in Lithuania as well since there is lack of relevantly recycled waste, whereas producers lack good quality recycled raw material. The quality of plastic waste recycling is directly related with their relevant identification.
In 2016, laboratory researchers applying equipment of integrated science, studies and business centre (valley) “Santaka”, specified methodology for plastics identification, which was used to identify polymer waste. Sorted plastic waste are used as secondary raw material for many products. This not only protects nature and primary natural resources, but also enables everyone to economize.
TESTING OF MATERIALS, ASSESSMENT AND ANALYSIS OF THEIR QUALITATIVE INDICATORS
Researchers of the Laboratory provide accredited Laboratory services, and perform material testing and assessment of their qualitative conformity. In 2015, the Laboratory was reaccredited to comply with the LST EN ISO/IEC 17025 standard. As a result of successful collaboration with economic entities, the Laboratory conducts research and provides consults on the quality issues of product manufacturing.
The Laboratory is accredited to carry out tests on:
- Plastic pipes (EN 1401, EN 12201, EN 13476, etc.);
- District heating pipes, pre-insulated bonded pipe systems (EN 253);
- Plastics and cellular plastics;
- Masonry mortars and plastering mortars (EN 998);
- Refractory products.
Laboratory researchers constantly analyze demands of clients and expand the scope of services provided both in accredited and non- accredited field. In 2016, they successfully participated in the comparative testings in Germany (Kunststoff-Institut Lüdenscheid and DRRR), a high level of excellence was approved in the field of plastics testing – the certificates were granted. While cooperating with business representatives a decohesion testing of electrofusion-welded plastic joints was performed.
Fig. 3. Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics
Fig. 4. Decohesion testing of electrofusion-welded plastic joints
In 2016, as a result of the investigations carried out by the researchers of the Laboratory, 5 articles were published in scientific journals referenced in Clarivate Analytics WoS database. The researchers participated at three international conferences.