–    safety assessment of nuclear power plants;

–    safety analysis of thermonuclear fusion reactors;

–    analysis of new generation nuclear power plants;

–    thermal-hydraulic analysis of accident and transient processes;

–    assessment of thermal-hydraulic parameters in NPP containments and other premises;

–    simulation of radionuclides and aerosols transport in the compartments;

–    assessment of nuclear reactor core modifications and analysis of postulated reactivity accidents;

–    reliability estimation and control of energy systems;

–    level 1 and level 2 probabilistic safety assessment of NPPs;

–    strength analysis of constructions, piping and components in complex technical systems;

–    failure analysis and engineering assessment for complex technical systems;

–    risk and hazard assessment of industrial objects;

–    assessment of security of energy supply;

–    modelling and reliability assessment of processes in net systems;

–    probabilistic modelling and analysis of unusual events;

–    sensitivity and uncertainty analysis of modelling results;

–    fundamental research in thermal physics.

 

In 2011, the researchers of the Laboratory, together with other national and foreign subjects, were implementing the following 25 projects: 3 state subsidy funded scientific research projects; 2 projects funded by the national research programme Energy for the Future; 17 international projects (6 projects of the EU 6th and 7th Framework Programmes (FP) and 6 international scientific research programmes without external funding); 3 projects funded by the Lithuanian economy subjects.

             

 

In 2011, two projects, financed by the Research Council of Lithuania, were continued as a part of thenational research programme Energy for the Future.

The aim of the project Research and Assessment Methodology of Energy Systems Reliability and Its Impact on Energy Security is to develop a common scientific assessment methodology and mathematical models of reliability for the Lithuanian energy systems. They would enable studying the reliability of energy systems and assessing the impact of reliability on the security of energy supply in Lithuania. The main elements in the Lithuanian energy system are electricity, gas and oil transmission networks. Individual methodologies of reliability research, assessment and its application serve as the basis of the general methodology for the reliability and risk assessment of electricity networks, developed during the implementation of the project. The general reliability assessment methodology is composed of special methods and methodologies developed in the scope of this project and intended to perform the following tasks: reliability assessment of individual electrical appliances, reliability research of the whole electrical power system (EPS), probability risk analysis of the main accident scenarios, development and application of a general reliability and risk model, analysis of statistical failure data and their application for assessing reliability parameters of network substations and their fragments, calculation of failure and reliability indexes of electricity transmission and distribution network, modelling and assessment of EPS static and dynamic operation modes, probability assessment and ranking of EPS operational modes. The developed individual methodologies define the use of reliability research methods and EPS models. To verify the reliability assessment methodologies of electricity networks, test calculations and result analysis were carried out. The analysis demonstrated a possibility to perform a reliability assessment of electricity networks which will enable estimating the impact of EPS reliability on energy security by applying integral assessment of reliability parameters and impact.

Heat, gas and oil are transmitted via pipeline systems and their reliability depends on the constituent elements, i.e. energy sources, pipelines and installed equipment. Reliability of pipes is closely related to many factors which may have influence on the structural integrity of their systems, and determine their operational lifetime. Failures of transmission and distribution networks, occurring during their operation due to the effect of external factors, corrosion-mechanical processes and loads resulting in thermal-hydraulic processes, not only cause disturbances in supplying energy resources, but may also endanger the safety of people and buildings due to possible explosions. In order to consider all the mentioned factors, an integrated methodology, encompassing probabilistic and deterministic methods, was developed for the reliability assessment. The developed methodology includes probabilistic safety analysis, system reliability theory, Monte-Carlo modelling, deterministic thermal-hydraulic analysis and deterministic probabilistic strength analysis of constructions, which is carried out using finite element method. Thus, a single methodology as well as the fundamentals and principles of its individual constituent parts and models were developed for all pipeline network systems. During the application of this methodology for different systems, the specificity of the systems is taken into account, i.e. heat/ energy-carrier, pipe degradation mechanisms, ageing of constructions, occurrence of loads, equipment used in these systems, statistical failure data and other factors that enable evaluating the reliability level of the analysed system. The applicability of the developed methodology was tested by carrying out experimental calculations for Kaunas heat supply networks.

Apart from reliability assessment methodologies of individual energy system networks, an integral reliability parameter assessment methodology of the Lithuanian energy system, which encompasses the networks and defines their interrelation, was developed. The basis of this integral methodology is the theory, methods and methodologies of research on reliability data and results. The methodologies define the use of reliability research methods and models of various energy systems (electricity, heat, etc.). In order to develop them, three separate research topics were distinguished, namely integral analysis of reliability parameters and research results; assessment of the reliability impact on the spread of disturbances and hazards in the network; modelling of the reliability impact on the common energy system. Moreover, methodologies and methods were developed for the analysis of the uncertainty of reliability parameters and sensitivity of results, integral assessment of energy system reliability parameters; mathematical modelling of the spread of disturbances in a network system with resistance, assessment of network system nodes resistance and parameters, modelling of the spread of hazards caused by disturbances and assessment of their parameters, modelling of reliability impact on the common energy system, and the analysis of reliability impact on the Lithuanian energy system. Together with the related models these methodologies enable the integral reliability research. Considering methodology and indicators developed within project devoted for the security of energy supply , new indicators for assessing the impact of energy systems reliability on the security of energy supply were proposed.

 

The project Development of Methodology for Energy Security Analysis and Integrated Security Level Assessment, which was implemented together with Vytautas Magnus University, was completed in 2011. The objectives of the project were the following:

1.   to develop an exhaustive methodology for energy security analysis, encompassing the research of challenges and disturbances to the energy system, modelling methods of energy system reaction to disturbances and their consequence assessment, and to adjust this methodology to the Lithuanian energy system;

2.   to develop a system for energy security level assessment (measuring), which would enable obtaining a single integral characteristic assessing both the security level of the whole energy system and the impact of various energy development scenarios on energy security.

 

This project is an interdisciplinary work encompassing modelling of energy systems, analysis of technical, economic, environmental, sociopolitical and other threats and their consequences, as well as the assessment of integral energy security level. For this reason, the project was implemented by the researchers of various fields (energy, mathematics, economics, political sciences, sociology). The novelty and originality of this work is signified by the interdisciplinary integration: the assessment of causes and consequences of energy system disturbances is complemented not only with technical and economic information about the system, but also sociopolitical assessment of threats and sociological analysis of consequences. Such integral methodology of energy security analysis has been developed for the first time and, in principle, has no analogues, although the 7FP and other international projects suggest that it is relevant and a great deal of effort is put into developing it.

To achieve a comprehensive energy security modelling and assessment, methodologies and methods were developed and tested by analysing specific examples of the Lithuanian energy system disturbances. As a result of the research, the following was achieved: a methodology for the analysis and assessment of threats to energy system was prepared; probability models for the calculation of threat transformation into disturbances, including the assessment of technical, economic and socio-political threats, were presented; two energy system models were developed for modelling energy disturbances and evaluation of their consequences. The first one is intended for modelling long-term scenarios of energy system development, and minimizing energy production costs and consequences caused by disturbances. The second model is based on probabilistic safety analysis and enables statistical assessment of all possible disturbance scenarios and their consequences. The obtained probabilistic characteristics of consequences provide preconditions for determining the most dangerous disturbances for energy system and the most effective protection measures in regard to energy security.

In the scope of this work, a methodology of energy security level assessment, based on the formation of security indicators and multi-criteria analysis, was also developed. The indicators encompass all aspects of energy security and enable expressing it by a single integral characteristic. The developed mathematical models of the dynamics of indicators and the assessment of their parameters by Bayes method provide for forecasting energy security level until 2025 and comparing the impact of different energy projects on the energy security level.

Moreover, a methodology for the assessment and analysis of threats and their socio-political consequences was also produced. The main geopolitical, competitive, monopolistic and other threats were analysed and a partially quantitative system for the evaluation of socio-political consequences of various threats was developed.

 

 

The researchers of the Laboratory are implementing both the preliminary work for new power plant construction, carried out directly under the order of Visaginas NPP and VATESI, and advanced international scientific research projects that are aimed at developing new nuclear reactors and solving other relevant issues, related to the nuclear safety. Additionally, the researchers take part in projects that aim at sharing knowledge in nuclear energy area with other national infrastructure organizations. These projects are important in strengthening the Lithuanian competence in the nuclear energy field which is necessary for every country owning nuclear power objects.

 

In 2011, under the agreement Update and Complement of Assessment of Potential Visaginas NPP Construction Sites in Respect of External Events between JSC Visaginas NPP and LEI, additional research was continued by analysing the following external factors: human induced events, meteorological phenomena and site flooding. The aim of this project is to assess the suitability of potential sites for VNPP construction following the Nuclear Safety Requirements, newly approved by State Nuclear Power Safety Inspectorate (VATESI) of the Republic of Lithuania, and the updated Safety Requirements of International Atomic Energy Agency (IAEA) as well as taking into account the results of up-to-date research and data. All work is divided into five separate tasks/ topics: Update of Hazards and Events Assessment, Detailed Assessment of Gas Explosion, Description of Possible Actions due to Extreme Situations, Description of Physical Protective Means Application Possibilities and Assessment of Ultimate Heat Sink Characteristics. In 2011, additional research was carried out by assessing unintentional human induced events, meteorological and flooding hazards, a technical certificate “Survey of Statistical Data and Probabilistic Methods” was prepared, and finally, the initial data and updated final reports of separate topics, agreed with the competent authorities, were submitted to the Client.

The results of the performed research may be important while making a decisions regarding a particular VNPP construction site and planning its risk management. Following the recommendations of IAEA, the analysis of external events should be updated if any additional information emerges in the future.

 

The scientists of the Laboratory of Nuclear Installation Safety have been actively participating in the activities of the European Technical Safety Organisations Network (ETSON) since 2009.

On 7-8 November 2011, the representatives of LEI and other ETSON organizations participated in the EUROSAFE forum Nuclear Safety: New Challenges, Gained Experience and Public Expectations organized in Paris. In cooperation withETSON organizations, reports were prepared and presented in a separate seminar “Experience Feedback on the Fukushima NPS Accident”. The first report of the seminar “Description of the Accident Scenarios, Current Status of the Reactors” was presented by the Director of LEI Prof. E. Ušpuras. The researchers of LEI also actively participated in the preparation of Position Paper of the Technical Safety Organizations: Research Needs in Nuclear Safety for Gen 2 and Gen 3 NPPs of ETSON. It introduces relevant and priority directions of research and development of nuclear energy safety, and highlights the collective opinion on priority research and development in the field of nuclear energy expressed by the related ETSON members (BELV – Belgium, GRS – Germany, IRSN – France, VTT – Finland, UJV – the Czech Republic, LEI – Lithuania, VUJE – Slovakia), associated ETSON members (SSTC – Ukraine, JNES – Japan) and safety regulatory bodies, directly enrolled into safety research programmes (CSN – Spain, SSM – Sweden, KFD – the Netherlands). The document was sent to the European Commission, International Atomic Energy Agency, Sustainable Nuclear Energy Technology Platform (SNETP) and other organizations in order to attract attention to relevant research directions in the field of NE safety and initiate projects for the implementation of such research.

In the second meeting of ETSON General Assembly, organized on 9 November 2011, a decision was made to integrate EUROSAFE working groups into ETSON network as umbrella groups (UG). Apart from three already existing umbrella groups (UG 1 – Preparation of Safety Assessment Manual, UG 2 – Scientific Research Programmes, UG 3 – Know-How Management), one more group (UG 4), intended for the research of Fukushima NPP, is going to be established. LEI and its representatives take active participation in all four ETSON umbrella groups. Twelve expert groups that deal with the most important fields of nuclear safety research were also established in ETSON network and the researchers of the Laboratory actively participate in the following eleven groups:

 

–    Operating Experience Feedback, including Incident and Precursor Analysis;

 

In 2011, according to the plans for the project IRIS International Reactor Innovative and Secure (IRIS) and the joint agreement between project participants and Westinghouse Electric Company LLC, the previously performed research for the preparation of the conceptual IRIS project was summarised and presented in a separate Chapter Analysis of Emergency Planning Zones in Relation to Probabilistic Risk Assessment and Economic Optimization for International Reactor Innovative and Secure of the book Nuclear Power Plants. IRIS project and the related research of Westinghouse Electric Company LLC were completed on 29 November 2010. More than 20 companies and 10 countries participated in the implementation of the project, which took 10 years. During this time, the researchers of LEI participated in the preparation of inter-comparative methodologies and work supervision related to the structural, economic, strength, safety and security research of new reactors. In the recent years, the specialists of the Laboratory of Nuclear Installation Safety have participated in performing IRIS probabilistic safety and economical efficiency analysis and research, devoted to reduce the risk of various external hazards and the uncertainty of the obtained results. As the building of a new NPP in Lithuania is planned, scientific research in this field is relevant for studying the construction of new reactors. The carried on contribution to IAEA technical documentation can be also mentioned as one of the most important activities.

 

 

The work of the project SARNET-2 was continued in 2011 (Grant Agreement was signed in 2009). This project aims at the integration of NPP severe accident and operational research in Europe. 41 scientific and business institutions from EU countries, including LEI, participate in this project. The researchers of the Laboratory take part in the activity of the three following working groups of the project:

–    WP4 ASTEC – modelling, adaptation and verification of integrated code ASTEC for severe accidents in NPP;

–    WP5 COOL – cooling of melted core and remaining debris;

–    WP7 CONT – analysis of processes in containments of NPP.

While implementing these activities, the researchers of the Laboratory participated in the meetings of ASTEC users and separate working groups. They also modelled processes in the INPP spent nuclear fuel pools in the cases of Beyond design basis accidents, and the ones taking place in the experimental facilities. The experiments of nuclear fuel assemblies overheating and fast cooling of damaged fuel, carried out in PHEBUS and QUENCH experimental facilities, were modelled. The modelling was performed using ASTEC and RELAP5/SCDAPSIM codes. The sensitivity and uncertainty analysis was carried out by applying methodology and SUSA code developed by GRS (Germany). In parallel, the analyses were performed with IRSN (France) SUNSET software as well. The specificity of application of these two methodologies for carrying out the analysis was discussed. A similar to the QUENCH experiments re-flooding of fuel assemblies was also modelled in case of an accident in spent nuclear fuel pools.

For analysis of processes in containments of nuclear power plants the processes of sprayed water droplets interaction with atmosphere as well as hydrogen mixing and combustion in the containments were investigated applying COCOSYS code. The researchers of the Laboratory modelled the experiments of water droplets evaporation (EVAP) and steam condensation (COND) carried out in the THAI facility. Apart from LEI, other 9 institutions took part in the benchmark. The results obtained by the researchers of LEI were in agreement with the results received by the most advanced organizations.

The participation in the SARNET activity, exchange of experience with the colleagues from other organizations and the analysis and modelling of processes carried out in experimental facilities provide a better understanding of computer codes and greater experience in modelling, which is required to carry out the analysis of real nuclear facilities.

 

The 7FP application Proposal for a Harmonized European Methodology for the Safety Assessment of Innovative Reactors with Fast Neutron Spectrum Planned to be Built in Europe (SARGEN_IV) was submitted to the European Commission in April 2011. It is coordinated by the Radioprotection and Nuclear Safety Institute (IRSN, France) and LEI is one of 22 European institutions which participate in the project. The application was approved by the European Commission in June, and a grant agreement was signed between the EC and the coordinator, IRNS in October. A consortium agreement on this project is going to be signed between the coordinator and every scientific research institution participating in the project in the beginning of 2012.

In the scope of the projects, the researchers of LEI are going to take part in the activities of the following three working groups: (1) review of safety assessment methodologies of innovative reactors; (2) experimental application of the European safety methodologies; (3) development the European Action Plan for the scientific research and technologies of fast neutron reactor safety. LEI is going to coordinate the activity in the Task Review of available international documents for the safety assessment of Generation IV reactors in the first mentioned working group.

 

PHEBUS-FP programme is one of the largest international research programmes for water-cooled nuclear reactor safety and severe accident research. IRSN (France), which initiated the programme in 1988, is presently coordinating it and the Laboratory is continuing the research in its scope. Applying COCOSYS code, the Laboratory performs simulations of the phenomena in PHEBUS containment. In 2011, continuing the cooperation with GRS mbH (Germany), an integral model of containment, which enables a detailed analysis of processes during the FPT-2 experiment, was developed. The researchers of the Laboratory were responsible for modelling thermal-dynamic as well as aerosol and radionuclide transport processes, while GRS mbH complemented the model with the description of chemical transformations of iodine. The performed analysis demonstrated that the jointly developed model may be successfully applied for modelling of all processes in the PHEBUS containment. It also enabled continuation of the long-term cooperation between GRS mbH and the LEI.

 

 

On 13 December 2010, a new agreement on the EU 7FP project MATerials TEsting and Rules was signed. This project started on 1 January 2011. The laboratory of Nuclear Installation Safety and the laboratory of Materials Research and Testing are participating from LEI. Its main objective is to carry out detailed research of material behaviour during the operation of generation IV reactors. The project includes the following activities:

–    Mature materials research focused on testing procedures for the new reactors conditions;

–    Supporting experiments of mature materials aimed to liquid metals characterization and to pre-normative qualification.

–    Pre-normative activities, comprehensive of experiments, to revise and update the design rules.

 

The research of the project is divided into 15 work packages and the representatives of LEI participate in two of them, namely the 6th package Manufacturing and Welding and the 7th package Testing Activities in Support of Design. The fatigue test of the cross-weld specimens in air at 550 ^oC temperature will be performed. The results of the experiments will be used for calculation of the weld coefficients.

In 2011, the analysis of standard documents and other literary sources related to the research of weld fatigue under controlled strain at high temperature was carried out. Following the most successful research of the European scientific institutions, information obtained during consultations and worldwide standards applied for weld tests and research of their properties, experimental procedures and methodology of weld fatigue under controlled strain at high temperature were developed.

 

In 2010, LEI continued activities of NULIFE (Nuclear Plant Life Prediction) network of excellence. One of the main tasks is to create a single organisation structure in the form of a Virtual Institute, capable of providing harmonised R&D at European level to the nuclear power industry and the related safety authorities in the area of lifetime evaluation and management methods for structural components.

This project is also related to the methodology improvement of decision-making, based on risk assessment, and optimization in service inspection. The implementation of the project is carried out by a consortium of participants from 10 contractual organizations and 27 partner organizations. The coordinator of the project is VTT scientific research centre (Finland).

In 2011, the researchers of the Laboratory participated in the activity of the Expert Groups (IA-2) and specialised group for Proposal Preparation (RA-9). Expert Groups (IA-2) prepared the material on “Leak Before Break” methodology applied for austenitic pipeline of RBMK-1500 reactor circulation contour. The material was used for the formulation of the report on national experience in the application of “Leak Before Break” methodology for the assessment of safe operation of pipelines. Moreover, the researchers took part in the workgroup preparing the report Impact of Passive Components on Security and together with NUCLIFE partners from other countries prepared the proposals for FP projects Improved Safety Assessment Procedures based on Probabilistic Considerations (PROSAFE) and Leak before Break in Long Term Operation (LAGOON).

On 14 November 2011, the association NUGENIA uniting the networks of excellence, SNETP, Gen II/III, NULIFE and SARNET, was founded. The set aims of the Virtual Institute NULIFE correspond to the aims of the established association, i.e. technical maintenance of the II and III generation reactors running in the EU countries and scientific research of their lifetime assessment. 7 areas for research and development were also established, namely: nuclear fuel and waste; structural integrity, material ageing and lifetime; safety and risk assessment; severe (beyond) accidents; core and reactor operation; innovative Gen III design; harmonisation activities.

 

 

In accordance with the agreement between the Institute for Energy at the Joint Research Centre of the European Commission (EC JRC IE) and LEI, the implementation of the research on Reliability and Data Analysis of Passive Components was completed in 2011 and the research report Age-Dependant Reliability Analysis and Risk Minimization for Passive Components was updated. The performed research is related to the APSA research network coordinated by EC JRC IE and representing the Network for Incorporating Ageing Effects into PSA Applications and also related to the already-mentioned EU NULIFE network of excellence. 14 organizations from different countries participate in the APSA research network. Taking into account the impact of equipment degradation and change of their reliability characteristics,the organizations aim at the improvement of the classical probabilistic safety assessment. The application of the classical PSA on the basis of the assumption of constant reliability characteristics sometimes results in an practically and theoretically inadequate safety assessment. In order to perform age dependant PSA, a larger amount of data, inspection assessment and more detailed models are essential.

Continuing the work in the scope of this network in recent years, LEI has devoted most of attention to activities, related to the component reliability analysis methods (mostly to the Bayes method) and time dependent reliability characteristics assessment as well as application of such methods and estimates in probabilistic models. Furthermore, the issues of development and application of reliability database and relevant software (e.g. WinBUGS) were considered.

 

In 2011, LEI, as the member of ENIQ (European Network for Inspection and Qualification) coordinated by EC JRC Institute of Energy, continued the participation in the activities of working group on risk analysis TGR (Task Group on Risk). The researchers participated in the preparation/review of technical documents describing the best European practice in the field of risk-informed inspection programme development and optimization. TGR group of ENIQ research network is comprised of 20 different organizations. Activity of this network is related to the EU NULIFE network of excellence and other FP7 projects.

 

 

The European Nuclear Safety Training and Tutoring Institute (ENSTTI) was established in 2010 by ETSON organizations, urged by the Institute for Radiological and Nuclear Safety (IRNS). Recently there are four members in ENSTTI: BELV (Belgium), IRSN (France), GRS (Germany), and LEI (Lithuania). ENSTTI provides vocational training and tutoring in methods and practices required to perform assessments in nuclear safety, nuclear security and radiation protection. The institute encourages technical support organizations to share experience in order to improve nuclear safety by spreading knowledge and practical experience in the field of nuclear safety culture.

Last year, ENSTTI organised two events: a winter seminar Nuclear Safety Fundamentals which took place on 7–10 February in Slovakia and 4-week summer training (27 June – 22 July) in Germany (GRS). The researchers of the Laboratory gave lectures on the NPP dismantling strategies and particular issues of Ignalina NPP dismantling. 15 participants from four European organizations, namely Areva, Bel-V, IRSN and GRS, participated in the summer training. In the future, ENSTTI is expected to become even more active since it has submitted applications to IAEA and the European Commission regarding the organization of similar training.

Participation in the mentioned activities enables acquiring experience in organizing similar courses and improving qualification. Such activities may be necessary after the beginning of Visaginas NPP construction when providing qualification for new staff at the power plant and supervisory institutions.

Continuing the cooperation with the European Technical Support Organizations, in May 2011, LEI signed and agreement with RISKAUDIT IRSN/GRS INTERNATIONAL (GEIE), established in France, in regard to the participation in the project Transfer of Western European Regulatory Methodology and Practices to the Nuclear Safety Authority of Belarus - Institutional and Technical Cooperation with Gosatomnadzor to Develop its Capabilities on the Basis of Transferred Western European Safety Principles and Practices, organized by the European Commission and RISKAUDIT. Under this agreement, the researchers of LEI take part in the activity of the following four working groups: (1) development of nuclear safety legislation; (2) support of nuclear safety licensing by establishing a regulatory institution and developing its functions; (3) training of the employees at the regulatory institution; (4) training of the employees at the educational institutions of the Ministry of Emergency Situations. In cooperation with the project partners, the specialists of the Laboratory participated in the workshops, organized by different working groups, where they presented international nuclear safety requirements and the experience of the European regulatory institutions and technical support organizations related to nuclear power plant safety assessment and licensing of nuclear objects. Moreover, the researchers of the Laboratory took part in the workshops for training the representatives of Belarus to use software packages applied for the analysis of accidents in nuclear power plants. In total, the researchers participated in five workshops in 2011.

LEI was appointed as the leader of the fourth working group and is coordinating the activity of the Lithuanian, Ukrainian and Finish specialists in organizing and running workshops for the employees at the Ministry of Emergency Situations of the Republic of Belarus. In September 2011, the researchers of the Laboratory organized a five-days workshop in the town Svetlaya Roscha, Belarus. Together with the Ukrainian and Finish partners, they presented the main principles of nuclear safety, and introduced the participants to the functions of nuclear safety, emission of radioactive materials during accidents in nuclear power plants, environmental impact and management of emergency situations. A similar workshop, focused on the emergency preparedness in nuclear power plants (on-site) and off-site as well as public information on accidents, is planned next year.

Such support, provided for the neighbouring country, is necessary in order to ensure timely and efficient supervision of the newly-built nuclear power plants in Belarus by its nuclear regulatory institutions, which is especially important not only to Belarus, but also Lithuania (as the plants are going to be built close to the Lithuanian-Byelorussian border) and all Europe.

                  

 

Scientific research of thermonuclear fusion energy (FUSION) development is one of the priorities of the EU FP7. While implementing the research of this field, LEI continued the work described in 7BP EURATOM – LEI Association Agreement. In 2011, cooperating with Max-Plank-Institut für Plasmaphysik (Greifswald, Germany), safety analysis was carried out to assess the capacity of plasma vessel venting system. The analysis of the processes in the cooling system was performed by applying RELAP5 code, while COCOSYS code was used to investigate the processes in plasma vessel.

 

In 2010, an agreement was signed on Limit Analysis of the Port Welds between the Plasma Vessel and the parts in the W7-X Cryostat System with Max-Plank-Institut für Plasmaphysik and the project was completed in December 2011. The aim of the project was to prepare the finite element models of port welds of the plasma vessel and perform a strength analysis, which was done using ABAQUS/Standard software, intended for solving linear and non-linear problems under static and dynamic loads. The software also enables carrying out strength analysis of components made from different geometric forms. The structural integrity analysis of the welding connections was analysed for the following ports / port combinations:

–    port AEQ20 given 1 mm thick weld;

–    port AEK20 given 1 mm thick weld;

–    port AEU30 given 1 mm and 6 mm thick welds.

 

The prepared geometric models were transferred to the finite element software ABAQUS/Standard which was applied for preparing finite element models of port welds of the plasma vessel. The analysis was carried out under the set loads and in the limit case using global scaling factors (SF) 3.0. According to the results of analysis it is possible to conclude that the stability of the all welding between Plasma Vessel and ports will be sustained at all used loading for analysis. In case of limit analysis it was not detected the fact that displacement of the point where loads are applied starts to increase very rapidly and the convergence was never lost during the analysis. The results show that biggest plastic strain was occurred in port AEU30 with gap 6 mm. The biggest displacement was occurred in this port also. The figures (a-d) present the prepared models of this port weld and some of the obtained results.

 

 

The state subsidy funded research project Numerical and Experimental Research of Condensing Two-Phase Flow was successfully completed. During its implementation, a numerical model for thermal-hydraulic system, which uses condensation implosions for circulation, was developed and its practical applicability was justified. This suggests that having analysed and mastered this process, its use for passive return (without external energy) of liquid heat-carrier to the boiler of actual thermal equipment will become possible.

Some significant results were also obtained from the research of the impact of condensation on stratified coocurrent flow in a closed horizontal channel. It was determined that condensation influences hydrodynamic boundary layer of the steam flow. The impact of condensation on interphase friction was modelled using the data obtained by natural experiments, which enabled the application of the simple numerical single-phase flow model FLUENT3D.

The experimental research was carried out using high-speed thermographic technique, which was applied a specially developed methodology for temperature profile measuring. Recommendations for its usage were provided, and the speed of 25 measurements per second with the resolution of 10 measurements for 1 mm of the cross-section was achieved.

 

 

A three-year state subsidy funded research project Analysis of Processes in Complex Technical, Natural and Social Systems Applying Best Estimate Methodology, initiated in 2010, was further continued in 2011. Laboratory of Hydrology and Laboratory of Energy Systems Research also take part in this project which is a continuation of previous common work performed by the three laboratories. The objective of this project is to apply the uncertainty analysis methodology in the field of engineering and social sciences and for modelling the hydrological processes.

Performing the numerical research in technical systems, the processes taking place during severe accidents in nuclear reactors were modelled. The best estimate methodology, ICARE module of ASTEC code, as well as SUSA and SUNSET packages were applied for modelling the FPT1 experiment carried out in PHEBUS experimental facility. The best estimate analysis demonstrated that having assessed the applied uncertainties of the physical and software parameters, ICARE module is capable to simulate the main processes taking place in the fuel during severe accidents. Specific aspects of the application of different codes were also determined.

In 2011, the uncertainty and sensitivity analysis was carried out to examine the impact of shifting to the broader use of biofuel on the Lithuanian economy. The uncertainty and sensitivity analysis methodology devised by GRS (Germany) and SUSA code were used to determine the parameters that have the greatest influence on both the trade balance and general value-added. The obtained results are going to be applied for the development and improvement of more implicated tools for energy-economy interrelation analysis.

Best estimate methodology was used for solving issues related to the environmental system: the influence of uncertainty of the elements of long-term water balance of the Curonian Lagoon on the water balance calculation results was assessed. The performed uncertainty and sensitivity analysis revealed the parameters of hydrological modelling that have the greatest impact on the balance; i.e. the parameters that require further revision in order to calculate the water balance of the Curonian Lagoon.

 

 

In 2011, a three-year state subsidy funded research project Lithuanian Energy Security Research was completed. Its main result is the estimation of the Lithuanian energy security level during various periods of time till 2025 and its comparison to the energy security level of the USA.

 

 

In cooperation with their partners, the researchers of the Laboratory of Nuclear Installation Safety participate in the projects for the decontamination and dismantling of Ignalina NPP equipment (B9 projects).

Last year, the Laboratory received an official letter from the INPP about the successful completion of the project Development of the Ignalina NPP 117/1 Building Equipment Decontamination and Dismantling Project (B9-0). It is the first project in Lithuania devoted for dismantling and decontamination of NPP equipment. The project was implemented by Babcock Nuclear Limited (United Kingdom), Nukem Technologies GmbH (Germany) and LEI consortium. The main objective of the project was to prepare an optimal dismantling and decontamination strategy for emergency cooling system of RBMK-1500 reactor and other equipment, which is located in building 117 / 1 of Ignalina NPP, as well as to develop the design and safety justification documentation necessary for implementing the project, and to provide support for the Client during the licensing (i.e. coordinating the prepared project documentation with the Lithuanian Authorities) and during the implementation of the project.

In the end of 2010, the State Nuclear Power Safety Inspectorate (VATESI) granted permission for initiating the decontamination and dismantling of equipment in the INPP Building 117/1. The possibility to provide support for INPP in carrying out the work was included into the B9-0 project, but the INPP decided not to take it and manage without the help of the Contractor (consortium) in the stage of project initiation. As stated by the representatives of the INPP, this shows the trust of the Client in the work done during the previous stages, i.e. preparing the documentation of the project and agreeing it with VATESI.

 

Development of the Ignalina NPP V1 Building Equipment Decontamination and Dismantling Project (B9-2) was continued in 2011. This project is under the implementation of Babcock (United Kingdom), LEI, Nukem Technologies GmbH (Germany) and Ansaldo (Italy) consortium. Its main objective is to prepare an optimal dismantling and decontamination strategy of the equipment, which is located in Ignalina NPP V1 building, as well as to develop all design and safety justification documentation necessary for implementing the project, and to provide support for the Client during the licensing and implementation stages of the project. A number of systems, located in Ignalina NPP V1 building, are to be dismantled and decontaminated, i.e. reactor gas circuit, exhaust gas cleaning system, system of reactor repair cooling tanks, ventilation system and emergency cooling system of the reactor. The researchers of the Laboratory also participated in the preparation of the Detailed design documentation and provided support during the licensing of Safety Justification Report. The preparation of the Detailed design documentation is going to be finished and agreed with the Client in 2012; the work related to the licensing of the project documentation is also going to be completed.

 

According to the agreement with GNS (Gesselshaft für Nuklear-Service mbH, Germany), a project Modification or Replacement of the cask handling Systems in the Spent fuel halls (SPH)at Ignalina NPP was continued in 2011. The work is carried out in cooperation with SC TECOSand AB machinery plant ASTRA. During its implementation, 6 shock-absorbers (3 in each INPP unit) and other equipment for cask handling are going to be produced and installed in the spent fuel halls of the NPP. The purpose of the main equipment, i.e. the shock-absorbers, is to absorb energy in case of earthquake or drop of containers filled with spent nuclear fuel, ensuring that the loads on the building and container constructions will not exceed the allowed limits. In 2011, shock-absorbers Type 1, cask service station and steel cover metal overlay of the INPP pool 338/1 were manufactured. During the manufacture stage of the shock-absorber, technical improvements of equipment (design optimization of lugs for shock-absorbers, etc.) were discussed and adopted in regard to the request of the Client.

 

During the second-year of project implementation, coordinated by LEI Energy Efficiency Research and Information Center, the researchers of the Laboratory developed so called laboratory and early prototypes of Energy Simulator as one of the ICT component of the DEMI project and initiated the implementation of all planned tasks in order to develop the final prototype. Moreover, the development of the model for estimating the energy, consumed in the process of steel construction treatment, was initiated by applying (a partially modified) design and modelling concept of a compressed air system. Practical usage of compressed air modelling as well as modelling of other systems is intended for the preservation of the common structure of model configuration and relevant data.

On the basis of the acquired experience in hybrid system modelling and modern possibilities of ICT, universal software and related modelling methods for designing industrial systems were developed. Such tools of modelling and energy consumption estimation operate in accordance with system configuration, design requirements and boundary conditions, which are remotely defined by Energy Analyzer. System models, representing different controlling of a system and its processes variables (e.g. air pressure and flow) as well as different operation conditions (e.g. consumption of compressed air), are developed using MATLAB (Simulink and SimScape) software and applying tools created for automatic modelling and energy consumption estimation.

 

In 2011, LEI started a new research in the risk and vulnerability assessment area of critical infrastructures (CI). In the scope of this topic, the Feasibility Study on Application of Decomposition Methods for Complex Networks was initiated in 2011 under the agreement between the Institute for Energy at the Joint Research Centre of the European Commission (EC JRC IE) and LEI. Many of the CI infrastructures, especially the ones in the energy sector, are complicated network systems (e.g. electricity system, gas or oil transportation and distribution systems). The analysis of such integrated systems is complicated and requires vast human and technical resources due to its scope. One of the possible solutions to such problem is the application of decomposition method: the problem is divided into simpler problems according to predefined rules and then the obtained results are recombined in order to obtain solution for the initial problem. During the feasibility study, possible application of the decomposition method for analysis of complex networks as well as the advantages and drawbacks of the method are going to be assessed.

 

After coming across the material of the seminar Future of standardization of Risk-Based Inspection and Maintenance in Europe, based on further development of CWA 15740, which was held on 15 February in Munich, the researchers of the Laboratory joined the implementation of the RBI Atlas project. The project and seminar were arranged in regard to the already completed and newly organized activity of European Virtual Institute for Integrated Risk Management (EU-VRi).

RBI Atlas project is intended for the European harmonization of the various EU national regulatory requirements in the area of risk-based inspection and maintenance. The inspection and maintenance must ensure that the accepted level of risk related to safety, health, environment and business/production/operation is achieved. The main objective of RBI Atlas project is to support the development of the European Standard for the relevant area. The future development of the Standard is based on the frame of the CWA (European Committee for Standardization – CEN Workshop Agreement) 15740:2008 which specifies the essential elements for risk-based assessment of industrial assets according to the RIMAP (Risk-based Inspection and Maintenance Procedures for European Industry) approach. To reach this aim, the company Steinbeis Advanced Risk Technologies (R-Tech) has collected information on the inspection practices followed in various European and non-European countries and represented it in the so-called RBI Atlas. It shows the status of Risk Based Inspection in each country representing it as the current allowed, not allowed or conditional. In order to update the information about the current RBI status and promote the cooperation, R-Tech is searching for competent persons and institutions in different countries. In such way, the information about Lithuania was updated after LEI had joined the project in 2011. For future cooperation, the representative of LEI is informed about other projects and new EU-VRi activity.

 

 

In 2011, there were 13 doctoral students in Laboratory of Nuclear Installation Safety who, together with experienced scientists, presented the research results in science research reports. 60 scientific articles were published (including 12 articles in ISI indexed journals) and 37 papers were presented in scientific conferences. The researchers of the Laboratory participated in the events related to nuclear energy and presented papers in all main international conferences, where safe operation of nuclear power plants and physical phenomena occurring in them were analysed. The researchers actively participated in different international and national training courses, IAEA seminars, committee and coordinating meetings, activity of FUSION development committees and other organizations and scientific institutions.