Scientific Divisions / Nuclear Engineering Laboratory (14)
MAIN RESEARCH AREAS OF THE LABORATORY:
- Investigation of thermal processes in energy equipment components:
- Research of heat and mass transfer in the equipment of biofuel-fired objects; reduction of emission along with flue gases resulting from biofuel combustion using electrostatic precipitators;
- Forced and mixed convection, turbulent and transition flow regimes, single-phase and two-phase flows, influence of channel geometry, variable physical properties, roughness and centrifugal forces;
- Numerical modelling of heat transfer and hydrodynamic processes in various channels and geological structures;
- Safety of spent nuclear fuel (SNF) management: modelling of fuel characteristics, safety and environmental impact assessment of storage and disposal facilities, normative and legislative base;
- Safety of radioactive waste management: safety and environmental impact assessment of treatment technologies and storage and disposal facilities, normative and legislative base;
- Evaluation of different factors related to decommissioning of nuclear power plants: planning and cost of decommissioning and dismantling; radiological characterisation of the area, buildings, systems and equipment; safety and environmental impact assessment of individual facilities; normative and legislative base;
- Fire safety assessment in nuclear power plants and other important facilities;
- Research related to construction of the new nuclear power plant in Lithuania.
Researchers of Nuclear Engineering Laboratory together with other laboratories of the Institute coordinated and implemented two long-term scientific research and experimental development programmes:
• Investigation of single-phase and two-phase flow dynamics, heat and mass transfer processes (2012–2016).
The objective of the programme is to develop research methods and perform investigations of the single-phase and two-phase flow structure, heat and mass transfer regularities in dealing with the efficiency of new heat energy production from biofuel schemes, energy and mass flow measurement and heat and mass transfer intensification tasks under transient flow conditions, flow in transition region, impact of physical features and buoyancy forces and vapour condensation processes;
• Investigation of nuclear power plant decommissioning and nuclear waste and spent fuel management processes and radiation impact analysis (2012–2016).
The objective of the programme is to analyse and estimate the radiation impact on humans and the environment during manage¬ment, storage and disposal of SNF and radioactive waste by applying numerical and experimental research methods and taking into account the peculiarities of Ignalina NPP decommissioning processes.
RESEARCH OF THERMAL PROCESSES IN ENERGY EQUIPMENT COMPONENTS
The Laboratory carries out investigations of heat transfer and hy¬drodynamics in energy equipment for different purposes (in elements of nuclear reactors, various heat exchangers, etc.). In both laminar and turbulent flow cases, surface roughness, centrifugal and buoyancy forces (mixed convection) can impact heat transfer in many energy installations, which, under certain conditions, can become a reason for an accident in different installations. Therefore, in order to analyse such problems in depth, the Laboratory performs experimental mixed convection investigations in various channels. In parallel, numerical investigation is also performed using ANSYS CFD code (ANSYS, USA), which is widely applied in the world for modelling fluid movement and heat transfer in complex two-dimensional and three-dimensional systems. Taking into consideration the flow mode, various models of laminar, transitional and turbulent transfer are used. Additionally, such research was initiated in geological structures while analysing the disposal possibilities for Ignalina NPP spent nuclear fuel.
In 2012, the Laboratory participating in activity of the project Santaka Valley by the open access scientific research and experimental development (R&D) centre obtained LDA and PIV equipment, which has been designed to investigate flow structure in gas and liquids in a wide range of velocity variation. This equipment can measure flow velocities, pulsations, and vortex rotational frequencies, and it can visualize them, etc. Furthermore, the Laboratory obtained liquid crystal thermography equipment enabling researchers to measure temperature of various objects and variation of temperature of an individual visual part of an analysed object in the remote non-invasive way.
Biofuel is rather widely used in many countries for heat and electric power production. Biofuel (wood, straw, grain, etc.) is considered a renew¬able energy source causing the least environmental impact; this is why its consumption increases not only in the newly built, but also in the reconstructed boiler houses in Lithuania. However, one of the major drawbacks comparing biofuel combustion to gas or liquid fuel combustion is that the release of solid particles into the environment is quite large. With increasing number of devices burning biofuel, the emission of solid particles increases. Due to the harmful impact to the human health, the amount of solid particles in the flue gas of the combustion devices is being limited, i.e., various filters that capture these solid particles are installed. Efficiency of cyclones and other mechanical devices capturing solid particles usually used in Lithuania is too small to capture small particles streaming with the flue gas; by means of electrostatic precipitators, a very high efficiency of gas (flue gas) cleaning can be achieved. While burning fuel, solid particles of different sizes are emitted, and the composition of flue gas changes. Due to this, the efficiency of electrostatic precipitators changes. An exhaustive analysis of these factors makes solution of relevant issues related to upgrading technologies in the Lithuanian energy sector possible.
In the frame of the project Research of local fuel thermal decomposition processes by developing efficient and ecological technologies
(2012–2014), financed by the national research programme “Future Energy
” of Research Council of Lithuania, researchers of the Laboratory, together with other laboratories of the Institute, conducted investigations on cleaning flue gas. During the Project, an experimental device was manufactured and research was performed. A prototype of the electrostatic precipitator manufactured at the Laboratory was used for the research. Relative concentration of the particles was determined taking into consideration voltage supplied to the electrostatic precipitator when the discharge electrode is positive or negative. The conducted research enabled the researchers to determine the efficiency of the electrostatic precipitator.
Researchers of the Laboratory, together with other laboratories of the Institute, also implemented another project – Development of Innovative Thermal Decomposition Technology and its Application for Utilization of Sewage Sludge (INODUMTECH)
(2013–2015) – based on the measure of the third priority Strengthening Capacities of Researchers Promotion of High International Level Scientific Research of the programme for the development of the action of human resources approved by the Ministry of Education and Science. Sewage sludge is produced as a waste in Lithuanian wastewater treatment enterprises. While the infrastructure of wastewater collection and treatment expands, the amount of sludge generated during wastewater treatment increases proportionally. Vast amounts of sludge stored in sludge sites begin to evoke hazard for the environment and contradict sustainable development principles. Therefore, the most effective methods are searched to treat wastewater sludge. One of the most innovative methods for utilisation of sewage sludge is its gasification. Applying this technology, a valuable product is released from sludge during thermal decomposition – flammable gas, which may be used in heat and electricity production. Due to gasification process it is possible not only to reduce the volume of the generated sewage sludge and obtain additional energy, but also to reduce the environmental pollution. During the project, a technological device model of gasification process of up to 100 kW was developed. The model allows operation in automated mode. During implementation of this project, an experimental research of flue gas purification was performed. The research results demonstrated that when burning biofuel (wood pellets), solid particles with diameters ranging from ~0.4 μm to ~20 μm dominate in the untreated flue gases. Particles with the diameter up to ~4 μm constitute the largest part. Solid particles from flue gases are cleaned using an electrostatic precipitator. When voltage applied to the precipitator was 12 kV, the obtained results showed that the decrease of concentration of solid particles was ~99%.
Experiments with synthetic gases showed that during the experiment, the amount of solid particles gradually decreased, and the lowest concentration was recorded at the end of the experiment. During these experiments, efficiency of 75% in the electrostatic precipitator was achieved in the case of wood gasification, and 60% in the case of wood-sludge gasification.
Fig. 1. Condensing film flow in a channel modelled with ANSYS CFD software
In 2016, conduction of fundamental experimental and numerical research of single-phase flow mixed convection heat transfer and flow structure in a flat channel in turbulent and transitional flow areas continued, and a fundamental numerical research of two-phase flow in a tube bundle using the ANSYS CFD (USA) software were expanded. Most of the attention was devoted to the Volume of Fluid method and application of User Defined Functions. Preliminary modelling results of water vapour flow in a channel were obtained.
RESEARCH ON SAFETY OF SPENT NUCLEAR FUEL MANAGEMENT
After the Ignalina NPP had decided to use dry storage CASTOR® and CONSTOR® type casks for spent nuclear fuel (SNF) generated in RBMK-1500 reactors, back in 1997, researchers of the Laboratory started performing studies related to the safety assessment of SNF management, storage and disposal. The Laboratory carried out criticality assessments for casks with SNF under normal operational and accident conditions, variation of radionuclides activity during the storage period, radiation doses on the cask surface and at the specific distance from it as well as temperatures.
Implementing the research on SNF disposal in Lithuania, the Laboratory experts with the assistance of Swedish experts proposed concepts of a deep geological repository in clay and in crystalline rocks for SNF and long-lived intermediate level waste in Lithuania. The concepts on disposal are regularly reviewed and optimised taking into account international experience and physical, chemical, thermal and mechanical properties of a specific repository site. While analysing the possibilities of SNF disposal in Lithuania, the cost assessment of geological repository installation was carried out, and generic repository safety assessment was initiated.
The Laboratory, together with consortium GNS – NUKEM Technologies GmbH (Germany), implemented an extensive project Design and Installation of the Interim Storage Facility for RBMK Spent Nuclear Fuel Assemblies from Ignalina NPP Units 1 and 2 (2005–2016). On September 20, 2016 VATESI issued a licence to operate this interim storage facility. It is foreseen that all SNF from INPP polls will be transported to the interim storage facility by the end of 2022. Laboratory researchers prepared an environmental impact report as well as a safety analysis report for this interim storage facility (the operation time at least 50 years) and provide support in licensing the storage facility. In 2007, the Environmental Impact Assessment Report was approved by the Ministry of Environment; in 2009, the Preliminary Safety Analysis Report (PSAR) was prepared and agreed upon, and the license for construction of the new SNF storage facility was issued by VATESI. In 2010–2011, the PSAR Addendum, which presents the evaluation of safety aspects of management and storage of damaged RBMK-1500 nuclear fuel assemblies, was prepared and the last updates were introduced in 2016. In 2015–2016, taking into consideration certain changes in the technical design made during construction works of the SNF storage facility, the Updated Safety Analysis Report was prepared. In 2016, on the basis of this Report and other technical documentation, VATESI issued a licence to operate the interim SNF storage facility.
In 2016, while implementing the provisions of Directive 2011/70/EURATOM by the EU Council of July 19, 2011 and National development programme for radioactive waste management approved by the Lithuanian Government in 2015, Laboratory researchers together with Grota UAB specialists under the order of Radioactive Waste Management Agency (RATA) prepared a Geological repository development plan
. In this work, a thorough analysis of the national situation (legal-administrative basis, social, economical, technical, and institutional context) was carried out. The analysis justified the demand for the geological repository in Lithuania and forecasted mainly positive perspectives of the implementation of the repository. In accordance with the analogy of international standards and taking into account the national context peculiarities, the geological repository development plan (strategy for 2015–2076) has been prepared. Eight implementation steps are foreseen. According to the Project management methodology, activities related to the geological repository implementation in Lithuania are proposed to be grouped into five work packages. Sequence of activities is foreseen as well as their dependencies, importance, and a place in the sequence of a specific step and overall repository implementation. The prepared risk management methodology allowed identifying risks in various stages of the geological repository implementation. After performing a qualitative risk assessment, a plan of risk management measures was proposed. Also, financial analysis for the geological repository installation was carried out. Applying reference parameter values, a preliminary geological repository implementation cost in Lithuania was specified. After conducting probabilistic modelling using the Monte Carlo method (taking into account the parameter uncertainties, arising due to certain risks), the uncertainty limits of the repository implementation cost were re-estimated. Aiming to estimate probable Project financing schemes and sources, experience of other countries in this field was summarized, and good practice examples were chosen to be applied to the Lithuanian case.
Researchers of the Laboratory constantly participate in research projects and programmes coordinated by the IAEA. The following projects have already been completed: The Use of Numerical Models in Support of Site Characterization and Performance Assessment Studies of Geological Repositories
(2005–2010) and Treatment of RBMK-1500 irradiated graphite in order to meet disposal requirements in Lithuania
In 2016, another IAEA project, Investigation of RBMK-1500 Spent Nuclear Fuel and Storage Casks Performance during Very Long Term Storage
(2012–2016), was implemented and completed. This project was implemented within the framework of the general project Demonstrating Performance of Spent Fuel and Related System Components during very Long Term Storage
coordinated by the IAEA. Numerical investigations of radiation characteristics and neutron activation processes in construction materials of Ignalina NPP spent nuclear fuel dry storage casks CASTOR® RBMK-1500 and CONSTOR® RBMK-1500 during long-term storage were carried out. In 2016, the results and conclusions of these investigations were presented in the final project report.
Fig. 2. Neutron (n) and gamma (g) radiation input to the total dose rate of CONSTOR® RBMK-1500 cask
on the surface (0 m) and at a two meters distance (2 m)
In 2016, a new state budget funded scientific study — Investigation of reactor RBMK-1500 and its systems decommissioning process parameters and processes occurring at final radwaste management facilities
(2016–2018) — was initiated. Investigations envelope origination of radiological contamination, investigations of decommissioning process parameters of contaminated systems, as well as investigations of long lasting processes (neutron activation, heat dissipation and radionuclide migration) occurring at the facilities of final radwaste management. In 2016, investigations of characteristics of SNF storage casks during long-term storage (up to 300 years) were performed. By means of numerical methods, using SCALE 6.1 computer codes package, radiation characteristics of dry storage cask CASTOR® RBMK-1500 were determined and equivalent dose rate change during long-term storage was evaluated. Using SCALE package and MCNP 5 codes, modelling of neutron activation of CASTOR® RBMK-1500 cask components was performed and activities of induced radionuclides were obtained. The obtained activities were compared to the unconditional clearance levels of materials. Thermal analysis of CASTOR® RBMK-1500 cask was performed using ALGOR codes package for summer and winter conditions and the temperature distribution within the cask was obtained.
Analysis of SNF repository engineered barrier (bentonite) with respect to heterogeneity of hydraulic conductivity was carried out. The heterogeneity impact on radionuclide I-129 migration was also analysed. Using numerical modelling it was determined that under defined conditions, the process of bentonite barrier resaturation with water may last up to 170 years. Preliminary assessment results revealed that due to heterogeneous water saturation of the bentonite layer surrounding the SNF container, the water flow conditions change within the bentonite barrier environment. This also leads to different radionuclide I-129 migration into the surrounding geological environment in comparison to that in the case of bentonite barrier fully saturated with water.
Fig. 3. Distribution of radionuclide I-129 concentration around SNF disposal canister during material resaturation with water:
a) at time of canister emplacement; b) 50 years after canister emplacement;
c) 100 years after canister emplacement; d) 145 years after canister emplacement
Researchers of the Laboratory use computer codes packages SCALE and MCNP (USA) for modelling SNF characteristics (doses, criticality, evolution of radionuclide composition, etc.) PETRASIM (USA), AMBER (Quintessa, the United Kingdom) and GOLDSIM (USA) software tools are used for assessment of safety of radioactive waste repositories. Using this software, modelling of radionuclide/gas transfer (single-phase/two-phase flow) in porous and fractured medium is performed. Computer codes COMSOL (USA) and COMPASS (GRC, the United Kingdom) are used for evaluation of influence of thermal-hydro-mechanical processes on groundwater flow in geotechnical environments.
RESEARCH ON SAFETY OF RADIOACTIVE WASTE MANAGEMENT
Since 1994, the Laboratory has been actively involved in the analysis of the radioactive waste management problems at the Ignalina NPP. Laboratory experts, together with the experts from SKB International (Sweden), carried out several projects that assessed the existing Ignalina NNP waste storage facilities and the possibilities to transform them into repositories.
In 2004–2005, together with French companies Thales Engineering and Consulting, ANDRA and the Institute of Physics, PHARE project Safety Assessment and Upgrading of Maišiagala Repository in Lithuania was implemented. The Laboratory specialists participated in preparation of the Safety Analysis Report, developed the database containing information on radioactive waste stored in the Maišiagala storage facility, and performed a comprehensive nuclide composition analysis.
In 2002–2005, a great deal of attention was given to the siting of the new near-surface repository for radioactive waste in Lithuania, scientific research related to the radionuclide migration from radioactive waste repositories and its impact on safety. With the assistance of Swedish experts, researchers of the Laboratory determined the criteria for choosing a near-surface repository site, improved the reference design of a near-surface repository and prepared the implementation programme. The impact of heterogeneous (uneven) waste activity distribution on radionuclide migration from the model near-surface repository was investigated.
In 2006–2009, researchers of the Laboratory implemented the project Reconstruction of Ignalina NPP Bitumen Radioactive Waste Storage Facility (Building 158) into Repository. A long-term safety assessment of the planned repository was prepared. The assessment was based on possible engineering solutions for reconstructing the storage facility into a repository and on characteristics of the site environment and the disposal system components, i.e., radioactive waste, the storage facility and surface engineered barriers planned to be installed over the storage facilities.
In 2008–2013, the Laboratory, as a partner of a Lithuanian consortium (Specialus montažas-NTP UAB, LEI, Pramprojektas AB, Vilstata UAB) implemented the project Installation of Very Low Level Radioactive Waste Repository (Landfill). The Landfill repository is intended for disposal of very low-level radioactive waste generated during the Ignalina NPP operation and decommissioning. The entire Landfill facility will be comprised of three repository modules and a buffer storage, where waste will be stored until its disposal. In 2009–2013, researchers of the Laboratory prepared an Environmental Impact Assessment Report for the planned economic activity, two preliminary safety analysis reports (for buffer storage and waste disposal units), two general data sets, a final safety analysis report and waste package descriptions of radioactive waste packages intended for disposal.
In 2016, the Laboratory, together with NUKEM Technologies GmbH (Germany), continued implementing the project New Ignalina NPP Solid Waste Management and Storage Facility (2006–2018). This facility is intended for solid radioactive waste retrieval, sorting, transportation, treatment (following envisaged technologies), packaging, characterization and storage. The entire complex will feature several facilities located at two sites: a solid waste retrieval facility at the existing Ignalina NPP solid waste storage buildings and a new facility for solid waste treatment and storage located nearby the Ignalina NPP. In 2008, an Environmental Impact Assessment Report was approved by the Ministry of Environment. Also, two Preliminary Safety Analysis Reports (PSARs) were prepared: for the New Solid Waste Treatment and Storage Facility at the Ignalina NPP and for the New Solid Waste Retrieval Facility at the Ignalina NPP. The first PSAR was approved in 2009, and VATESI issued a license for the construction of the storage facility. In 2009, two more PSARs were prepared for the New Solid Waste Retrieval Facility for Retrieval Unit 1 and for Retrieval Units 2–3 at the Ignalina NPP. In 2010, both PSARs were submitted to the institutions for review. The first PSAR was updated following the recommendations by the institutions, and at the end of 2010 was approved by VATESI; in the middle of 2011, the permission to build the facility was received. In 2011–2014, the second PSAR was updated considering the recommendations of the institutions. In the late 2014, VATESI approved documents justifying safety for Waste Retrieval Units 2-3. In 2016, an updated PSAR was prepared for release. At the end of 2016, the Report was submitted to the INPP. Approval of the Report by VATESI will allow initiation “hot” tests of the facility.
In 2016, the Laboratory, together with partners from French companies AREVA TA and ANDRA and Lithuanian partners Specialus montažas-NTP UAB and Pramprojektas AB, continued the project Low- and Intermediate-Level Short-Lived Radioactive Waste Near-Surface Repository (Design) (2009–2016). The repository is intended for disposal of low- and intermediate-level short-lived radioactive waste generated during the Ignalina NPP operation and decommissioning. In 2010–2013, laboratory’s specialists were involved in the development of the preparatory reports: Basic Engineering Design Report for Low- and Intermediate-Level Short-Lived Radioactive Waste Near-Surface Repository, Waste Inventory Report and Site Confirmation Report etc. In 2014, researchers of the Laboratory finished the preparation of a Preliminary Safety Analysis Report and submitted it to the Customer. The conducted safety assessment covers the operational period and long-term safety (period after closure of the repository). In 2014, an Environment Monitoring Programme for the planned repository was prepared and submitted to the Customer. In 2015, the Preliminary Safety Analysis Report and the Environment Monitoring Programme were updated taking into consideration the comments from the Customer and submitted to authorities for review. Later (by the end of 2016) the Preliminary Safety Analysis Report was updated for further licensing stages of Low- and Intermediate-Level Short-Lived Radioactive Waste Near-Surface Repository Design.
In 2016, the Laboratory’s researchers, together with partners from Eksortus UAB and Grota UAB initiated Preparation of Maišiagala radioactive waste storage facility final decommissioning plan and environmental impact assessment of the planned economic activity in the context of the project "Decommissioning of Maišiagala Radioactive Waste Storage Facility" (2016–2018). The objectives of this Project are the following: prepare a final Maišiagala radioactive waste storage facility decommissioning plan and environmental impact assessment programme; to prepare a report for the planned economical activity; and, in accordance with regulation, to receive the decision required to obtain Maišiagala radioactive waste storage facility decommissioning license, which shall be issued by State Nuclear Power Safety Inspectorate.
In 2016, research on possibilities to dispose of irradiated graphite in a geological repository was developed in a new scientific work financed from the budget assets applying updated computer codes. C-14 (organic and inorganic) release from irradiated graphite and its migration into the geosphere was analysed, and the role of different components of the repository barrier system in crystalline rock was demonstrated.
Fig. 4. Results of local sensitivity analysis as maximal radiocarbon (C-14) flux to geosphere:
a) – inorganic C-14; b) – organic C-14
The Laboratory researchers gained experience from participation in IAEA coordinated investigation projects, such as Improvement of Safety Assessment Methodologies for Near Surface Disposal Facilities (ISAM)
(1998–2001), Application of Safety Assessment Methodologies for Near Surface Radioactive Waste Disposal Facilities
(2002–2005), and Disposal Aspects of Low and Intermediate Level Decommissioning Waste
Researchers of the Laboratory use AMBER software (Quintessa, the United Kingdom) for modelling migration of radioactive and non-radioactive contaminants in the environment. GARDENIA software (BRGM, France) is used for modelling water balance, forecasting underground water level, and evaluating scenarios of climatic change. EQ3/6 software package (Lawrence Livermore National Laboratory, USA) is used for geochemical research. The software enables compilation of models for the assessment of chemical processes taking place in analysed water/solid phase systems. Such models are necessary for modelling chemical changes of contaminants (radionuclides), solubility and sorption in water/solid phase systems.
EVALUATION OF DECOMMISSIONING
Back in 1998, researchers of the Laboratory initiated a research related to Ignalina NPP decommissioning. The experts participated in PHARE project preparing a Preliminary Ignalina NPP Decommissioning Plan (1998–1999) as well as a Final Ignalina NPP Decommissioning Plan (2002–2003). In 2005–2008, together with the Institute of Physics, the project Development of Radiological Characterization Programme for Equipment and Installations at the Ignalina NPP was implemented.
Since 2007, Nuclear Engineering Laboratory has actively participated in Ignalina NPP dismantling projects. The Lithuanian Energy Institute, as a partner of the consortium Babcock (former VT Nuclear Services Ltd) (the United Kingdom) – LEI – NUKEM Technologies GmbH (Germany), implemented a project Ignalina NPP Building 117/1 Equipment Decontamination and Dismantling (2007–2010). In 2009, specialists of the Laboratory prepared and coordinated with the institutions an Environmental Impact Assessment Report. In 2010, a General data collection on waste disposal was prepared. Specialists of the Laboratory participated during preparation of the Basic design, which in 2010 was approved and submitted to the Customer, and Detail design and Safety justification, which were approved by the institutions. Researchers of the Laboratory analysed the equipment in Building 117/1, the amount of accumulated waste and their characteristics and carried out the assessment of the planned economic dismantling and decontamination activity. On December 1, 2010, employees of the Ignalina NPP, based on the prepared documentation, began dismantling and decontamination of the equipment in Building 117/1. The activities were completed in October 2011.
Researchers of LEI Laboratory of Nuclear Engineering, also as a partner of the consortium Babcock (the United Kingdom) – LEI – NUKEM Technologies GmbH (Germany), implemented the project Ignalina NPP Building V1 Equipment Decontamination and Dismantling (2009–2012). In 2010, specialists of the Laboratory finished preparation of general data collection on waste disposal. In 2011, specialists of the Laboratory prepared an Environmental Impact Assessment Report and received approval from the Ministry of Environment. In 2012, Basic design and Safety justification were approved by the institutions, and Detail design was submitted to the Customer. In 2012, employees of the Ignalina NPP, based on the prepared documentation, began dismantling and decontamination works of the equipment in Building V1. At the end of 2013, dismantling stage D1 was completed. During it approx. 640 tons of equipment were dismantled. Implementation of dismantling stage D2 of Building V1 is planned in 2023–2028.
In 2016, Laboratory of Nuclear Engineering, as a partner of the international consortium (Specialus montažas-NTP UAB – FTMC – LEI – ATP (Bulgaria) – INRNE (Bulgaria) completed the project The Evaluation of the Material Backlog and Radiological Inventory of Kozloduy NPP Units 1 to 4 (2012–2016). The objective of the project is to carry out a detailed evaluation of the radiological status of the equipment, structures, compartments and the radioactive waste and assess the total radiological inventory and material backlog of the Kozloduy (Bulgaria) NPP Units 1–4 (WWER). During the course of the project, experts of the Laboratory developed data bases for storage of project results, performed verification calculations of neutron activation and dose rates for the structures of Unit 3 WWER-440 reactor and participated in preparation of the reports on the verification calculations of neutron activation and dose rates and well as on detailed evaluation of the radiological status of the compartments, structures and the surrounding territories.
In 2016, laboratory of Nuclear Engineering, as a partner of the consortium FTMC – LEI, started the project Assistance to INPP by Technical Support Organizations in the Field of Radiological Characterization for Block A1 (Reactor and Auxiliary Systems) (2016–2017). The objective of this project is to identify scaling factors for Ignalina NPP Block A1 (including Unit 1 reactor and its service equipment) and a corresponding nuclide vector which is the set of the scaling factors. The scaling factors will make it possible to calculate the activity of other radionuclides based on the activity measurements of the key gamma nuclides. The scaling factors will be used in further activities of the radiological characterisation while implementing Block A1 equipment dismantling and waste characterisation as well as classification. In 2016, the laboratory experts, together with partners, prepared the first report of the stage Theoretical analysis. The report contains the analysis of reactor and auxiliary systems contamination.
Fig. 5. Dr. E. Narkūnas with other participants of the IAEA and Ignalina NPP workshop
„National Workshop on Safety Analysis Reports and Environmental Impact Assessments for Complex Dismantling Projects“
in the storage pools hall at the Ignalina NPP
In 2016, researchers of the Laboratory further improved functionality of DECRAD and DECRAD-ACT software. The main objective for application of DECRAD software is the analysis of decontamination and dismantling of nuclear power plants, planning the demand for expenses, costs and personnel, calculation of personnel radiation doses, planning radioactive waste disposal and assessment of other parameters related to decommissioning. The software may be applied for planning and analysing decommissioning of different power plants, their individual buildings or units. Also, using DECRAD software, a Multi-criteria Decision Analysis may be performed, the AHP (Analytic Hierarchy Process) method used in parallel with DECRAD software is one of the most relevant methods for selecting the alternatives for dismantling nuclear facilities. DECRAD-ACT software expands the functionality of DECARD, and is designed to store and process the data on radioactive components of nuclear reactors. DECRAD-ACT software was used in the above-mentioned Kozloduy NPP project.
In 2016, researchers of the Laboratory were invited to participate as experts in the IAEA coordinated project Data Analysis and Collection for Costing of Research Reactor Decommissioning (DACCORD) (2012–2016). Its focus is representative input data and benchmarking data needed for the costing of research reactor decommissioning at preliminary planning stages.
In 2016, the impact of ionizing radiation on personnel and habitants while implementing Ignalina NPP decommissioning activities was estimated. Radiation doses of personnel were estimated applying DECRAD software and were compared with the real measurement results. The impact of radioactive emissions from the INPP into the environment on habitants is estimated applying the methodology prepared under the INPP operation conditions. After the INPP operation stopped and decommissioning activities were started, the nature of radioactive emissions changed. Consequently, the presumptions used for calculating dose conversion factors should be reviewed and, if necessary, specified. Specification of parameters used for calculating dose conversion factors was carried out as well as the uncertainty assessment of decommissioning duration.
Fig. 6. Radial distribution of neutron flux in one reactor RBMK-1500 graphite column
modelled using MCNP code: a) – fast neutron; b) – thermal neutron
Modelling of neutron, photon and electron (radiation) transport is performed using MCNP-MCNPX (Los Alamos National Laboratory, USA) computer code. Assessment of scattered gamma radiation from nuclear facilities (e.g., radioactive waste storage and disposal facilities) is performed using MICROSKYSHINE code. Effective dose to workers is assessed using VISIPLAN (SCK-CEN, Belgium) and MICROSHIELD (GroveSoftware, USA) codes. Modelling of emission dispersion from various contamination sources is performed by means of AERMOD VIEW (Lakes Environmental Software, USA) software.
FIRE SAFETY ASSESSMENT IN NUCLEAR POWER PLANTS AND OTHER IMPORTANT FACILITIES
Fire in nuclear facilities (NF), especially in nuclear power plants, may cause danger to safety, operability of safety important systems and serious unpredictable losses. Thus, it is a worldwide practice to analyse fire hazards in nuclear facilities. The key aim of such analysis is demonstration that the arrangement of systems important for safety and existing fire safety measures ensure the safety of a NF and comply with requirements of the national legislation as well as IAEA recommendations and good practice of other countries.
Since 2001, the Laboratory has been carrying out fire safety assessment in nuclear power plants and other important facilities. Researchers of the Laboratory, consulted by Swedish experts, have assessed fire safety of the Ignalina nuclear power plant (NPP) reactor Units 1 and 2.They have also assessed fire safety of some renewed Ignalina NPP compartments with changed designation and the newly designed Ignalina NPP SNF and radioactive waste storage facilities. An external fire impact on the Ignalina NPP New Solid Waste Treatment and Storage Facility has been assessed, and the fire hazard analysis in the most hazardous areas in case of an internal fire in the facility has been performed. In 2009, the impact of fire during the implementation of dismantling and decontamination of Ignalina NPP Building 117/1 was evaluated; also, fire safety of the newly designed buffer storage and disposal units of Landfill repository was assessed. In 2010, the impact of fire during the implementation of dismantling and decontamination of Ignalina NPP Unit V1 was evaluated. In 2012, basing on the Detail design documentation, fire impact on the buffer storage of the very low-level waste repository was determined. In 2014, during preparation of documents justifying safety of low- and intermediate-level short-lived radioactive waste repository, fire hazard analysis of this repository was done. In 2015, researchers of the Laboratory completed the research work Fire hazard analysis of bituminised radioactive waste storage facility (2014–2015).
In 2016 laboratory researchers prepared two fire hazard analysis reports related with fire assessment: Fire hazard analysis of Ignalina NPP very low level waste repository in accordance with the scenario “Fire in the repository fuel station during fuel filling into the vehicles” and Fire hazard analysis of Ignalina NPP solid radioactive waste retrieval and sorting facility in accordance with the scenario “Fire in sections of buildings 155, 155/1 during retrieval of solid radioactive waste”.
Fig. 7. Modelling of fire in sections of buildings 155, 155/1, during retrieval of solid radioactive waste
In order to completely ensure fire safety in these nuclear facilities, it was necessary to perform fire hazard analysis and demonstrate how the protection of the structures, systems and components of these NF against fire and its effects is ensured without disturbing the operability of systems important to safety. The fire hazard analyses were carried out applying engineering assessment methods and performing a wide range of numerical investigations. The issued reports provide conclusions and recommendations, the implementation of which will improve the fire safety of these facilities and reduce the negative impact caused by fire and its consequences. During numerical investigations, the modern fluid dynamics based computer program PYROSIM (USA) was used. This program is developed to perform various assessments of fire dynamics and its dangerous factors.
DEVELOPMENT OF NUCLEAR ENERGY IN LITHUANIA
In 2007–2009, researchers of the Laboratory, at the consortium with Pöyry Energy Oy (Finland), conducted research related to the construction of a new nuclear power plant in Lithuania. An Environmental Impact Assessment Program for New Nuclear Power Plant
and a New Nuclear Power Plant Environmental Impact Assessment Report
were prepared. In the EIA Report, possible environmental impacts of the construction and operation of the new NPP were assessed in cooperation with other Finish and Lithuanian institutions (Institute of Botany, Institute of Ecology and National Public Health Surveillance Laboratory). According to the EIA Report of 2009, positive conclusions of the competent authorities were made concerning the planned economic activity; therefore, following this EIA Report, the Ministry of Environment made a motivated decision on the construction possibilities of the new nuclear power plant in Lithuania.
LABORATORY PARTICIPATION IN EU FP7 AND HORIZON 2020 PROGRAMMES
Since 2008, researchers of the Laboratory have actively participated in the EU 7th Framework Programme funded scientific research, coordination and support activity projects. The following projects have already been implemented: Treatment and Disposal of Irradiated Graphite and Other Carbonaceous Waste (CARBOWASTE) (2008–2013), Fate of Repository Gases (FORGE) (2009–2013), New MS Linking for an Advanced Cohesion in EURATOM Research (NEWLANCER) (2011–2013), Sustainable network of Independent Technical Expertise for radioactive waste disposal (SITEX) (2012–2013).
In 2016, researchers of the Laboratory continued participation in three 7FP funded projects (2 of which are already completed) and, together with scientists from other countries, further implemented two activities in coordination and support projects of the EU programme Horizon 2020
:CArbon-14 Source Term (CAST)
(2013–2018). This project aims to develop understanding of the generation and release of C-14 from radioactive waste materials under conditions relevant to waste packaging and disposal to deep geological repositories. The project focuses on releases from irradiated metals, ion-exchange resins and graphite. The project is implemented by 33 partners from 12 EU countries and 3 non-EU countries. In 2016, information about radiocarbon inventory in and its releases from the reactor RBMK-1500 irradiated graphite was collected and updated. In addition, new models for estimation of radiocarbon inventory in Ignalina NPP graphite and migration were developed. After development of release models research of irradiated graphite radiocarbon release in the near field environment was performed, when irradiated graphite was disposed of in a deep geological repository. In March 2016, researchers of the Laboratory participated in the CAST work package 6 (WP6) meeting in Wettingen (Switzerland) and in September – in the workshop in Middelburg (Netherlands), dedicated to the dissemination of the CAST project activities and research results, where a presentation on the irradiated graphite disposal issues was made. In October 2016, the researchers participated at the second general assembly meeting and work packages meeting in Luzern (Switzerland), after that the Grimsel Test site was visited.Assessment of Regional Capabilities for New Reactors Development through an Integrated Approach (ARCADIA)
(2013–2016). The objective of the project is to support and develop nuclear scientific research in new EU states related to the development of IV generation reactors, devoting the main attention to ALFRED (lead cooled reactor) demonstrator. The project is implemented by 26 partners from 14 EU states. Researchers of the Laboratory participate in this project together with the Laboratory of Nuclear Installation Safety. In final project year 2016 separate reports for each work package were prepared, where experience of EU countries on nuclear energy object licensing issues was summarized, the infrastructure present in various EU countries was analysed, which could also be used in implementing ALFRED project, also strengths, weaknesses, possibilities and hazards were identified.Building a platform for enhanced societal research related to nuclear energy in Central and Eastern Europe (PLATENSO)
(2013–2016). The objective of the project is to enhance the capabilities of social research institutions in Central and Eastern European countries to take part in EU research with respect to governance, social and societal aspects linked to nuclear energy. The project is carried out by 19 partners from 12 EU states. A national strategy on social, societal and governance (SSG) issues for nuclear energy was developed in 2016. Final PLATENSO partner meeting took place in Warsaw (Poland), where the project achievements were presented and social platform perspective in the EU were discussed.Sustainable network for Independent Technical EXpertise of radioactive waste disposal: Interactions and Implementation (SITEX-II)
(2015–2017). This Horizon 2020
program Euratom Project, funded by the EU, is carried out by the Laboratory researchers and 17 organisations from other EU countries and Canada. A high level of scientific and technical expertise is necessary in order to evaluate the decisions, especially those based on the results of scientific research, ensuring the geological repository safety. In this context, the aim of the project is to demonstrate the cooperation means and possibilities identified during the previous project (EC 7FP SITEX, 2012–2013) that would allow creating a sustainable network for independent technical expertise of radioactive waste disposal in Europe. Activities of such network are based on scientific cooperation using equipment present is different institutions, present potential of knowledge and improving the specialists’ skills that are necessary not only for interpretation of scientific research results but also for execution of independent technical expertise. The independent specialists (network) are a tool to develop a dialog for technical issues between regulatory institutions, organisations carrying out implementation of a geological repository, and the public. While implementing this project in 2016 the laboratory researchers together with the Consortium partners analysed common scientific research possibilities of radioactive waste management organizations, technical support organizations and research institutions as well as means in the future EU joint research program, systemized information on the demands of technical specialists’ training, strategy and applied practice in the project implementing organizations, analysed SITEX network possibilities in this field, also took part in the working group preparing recommendations on relevant issues for technical expertise specialists.Joint Programming on Radioactive Waste Disposal (JOPRAD)
(2015–2017). The aim of this Project is to prepare a proposal based on which a joint programming on radioactive waste disposal could be developed. The Joint Programming would bring together at the European level those aspects of research and development activities implemented within national research programmes, where synergy from Joint Programming is identified. The Laboratory researchers participate in the Project as an interested group of researchers that provides proposals and information on the scientific investigation needs related to radioactive waste disposal in Lithuania. Two JOPRAD meetings took place in Bucharest (Romania) and Prague (the Czech Republic) in 2016. The first meeting (67 representatives from 17 countries participated) was devoted to the discussion on how to attract countries having less experience (including Lithuania) into the future common programme in the field of radioactive waste disposal. During the second meeting (80 participants from 19 countries), a vision was presented on how this cooperation could be implemented, and preliminary financing schemes were discussed.LABORATORY PARTICIPATION IN IAEA AND EU EVENTS
In 2016, the Laboratory researchers improved their qualification levels by taking part in eight events (technical meetings, workshops and conferences) organised by the IAEA:
On May 24–26 in Madrid (Spain), in International Conference on the Advancing the Global Implementation of Decommissioning and Environmental Remediation Programmes
On June 11-19, in Vienna (Austria) in Technical Meeting on the Learning from International Experiences Related to Stakeholder Involvement in Radioactive Waste Disposal
On June 27 – July 1, in Vienna (Austria), in Technical Meeting on Design Extension Conditions for Storage Facilities for Power Reactor Spent Fuel
On October 3–6, in Bure (France), in Technical Meeting of the Underground Research Facilities Network for Geological Disposal
On November 7–10, in Vienna, in Workshop on Safety Analysis and Safety Documents for Nuclear Fuel Cycle Facilities
On November 21–25, in Vienna, in International Conference on the Safety of Radioactive Waste Management
On November 28 – December 2, in Vienna, in Technical Meeting of the International Predisposal Network and the International Low Level Waste Disposal Network on the Management of Radioactive Waste Streams That Present Specific Challenges
On December 5–9, in Visaginas, in National Workshop on Safety Analysis Reports and Environmental Impact Assessments for Complex Dismantling Projects
On October 25–26, in Cordoba (Spain), the laboratory researchers took part in EU IGD-TP (Implementing Geological Disposal of Radioactive Waste Technology Platform), organized 7th knowledge exchange forum, where they got acquainted with the present situation of geological repository installation in EU countries, completed and implemented scientific research projects and the EU supported cooperation possibilities on this theme.
In 2016, the researchers of the Laboratory implemented two long-term research and experimental development programmes, initiated a new state budget funded scientific study, carried out three EU 7FP projects
(two of them were completed), and started two projects of the programme Horizon 2020
. They also carried out nine applied works and earned approx. 245 thousand euros. The researchers actively developed their expertise by participating in technical meetings and workshops of the IAEA and EU, delivered six presentations at international conferences (in Austria, Spain, Romania, and Lithuania) and four presentations at national conferences, published six scientific papers in journals listed in Clarivate Analytics
data base Web of Science Core Collection
. Dr. R. Poškas and Dr. A. Šmaižys, Laboratory’s senior researchers, were granted the silver medals of the Institute at the celebration of the Lithuanian Energy Institute 60th anniversary. Dr. A. Narkūnienė and Dr. D. Justinavičius were awarded written acknowledgments by the Lithuanian Committee of the World Energy Council.