– forced and mixed convection, turbulent and transition flow regimes, influence of channel geometry, variable physical properties, roughness, centrifugal forces and transients effect;
– numerical modelling of heat transfer in various channels and geological structures;
– reduction of emission resulting along with smoke from biofuel combustion using electrostatic precipitators; research of heat and mass transport in the equipment of biofuel-fired objects;
– safety of spent nuclear fuel management: modelling of fuel characteristics, safety and environmental impact assessment of storage and disposal facilities, normative and legislative base;
– safety of radioactive waste management: strategy, safety and environmental impact assessments 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 buildings, systems and facilities, safety and environmental impact assessment, normative and legislative base;
– fire hazard analysis of nuclear power plants and other large facilities;
– research related to construction of new nuclear power plant in Lithuania.
Research of thermal processes in energy equipment components
Laboratory carries out investigations of heat transfer and hydrodynamics in energy equipment for different purposes (in the elements of nuclear reactor, various heat exchangers, etc.). Since in both laminar and turbulent flow cases, the effect of buoyancy forces (mixed convection) on heat transfer is manifested in many energy installations, which under certain conditions can be the reason for an accident in different installations, therefore, in order to analyse such problem the laboratory performs experimental mixed convection investigations in pipes and has recently initiated the research in flat channels as well. Additionally, such research was initiated in geological structures while analysing the possibilities of Ignalina NPP spent nuclear fuel disposal. In parallel, investigation is also performed using the ANSYS FLUENT code (ANSYS, USA) which is widely used worldwide for modelling the fluids flow and heat transfer in complex two and three-dimensional systems. The Laboratory uses various models of the laminar, transition and turbulent transfer.
In 2011 the numerical investigations (using ANSYS FLUENT code) on heat transfer and hydrodynamics in flat channel for opposing mixed convection flows in the transition region were continued. The obtained heat transfer and flow hydrodynamics results change and expand the understanding on the transition from the laminar to turbulent flow under the impact of buoyancy forces.
Advanced countries pay a lot of attention to the reduction of negative environmental impact caused by various energy objects. The reduction of pollution is an especially relevant issue in solid fuel combustion and one of the means to achieve it is the use of electrostatic precipitator. It is an effective means for cleaning the emitted solid particles (especially small ones which are not captured by other filters (e.g.: cyclonic filters)). Electrostatic precipitators intended for deposition of solid particles and used in industrial and energy equipment are prevailing worldwide for reducing the environmental pollution down to minimum. The filters are usually used in medium or high capacity power plants fired by coal or similar type of fuel. These filters are also relevant for specific industrial companies (concrete production, waste incineration power plants, etc.) which emit hazardous materials together with smoke during the production process. The novelty lies in the combustion of different types of biofuel since depending on the burnt material, the operation (efficiency) of filters changes due to the influence of different sizes and composition of particles emitted with smoke. An exhaustive analysis of these factors enables solving relevant issues related to upgrading technologies of the Lithuanian energy sector.
The Laboratory initiated research in this field in 2011 and carried out the review of electrostatic precipitator usage worldwide.
Safety of spent nuclear fuel management
After the decision to use dry storage facility for spent nuclear fuel (SNF) at Ignalina NPP in CASTOR and CONSTOR type casks, the Laboratory started performing studies related to the safety assessment of SNF management, storage and disposal in 1997. The Laboratory carried out criticality assessments for the 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 of the cask.
Implementing the research on SNF disposal in Lithuania, the Laboratory experts with the assistance of Swedish experts proposed the concepts of deep geological repository in clay and in crystalline rocks for SNF and long-lived intermediate level waste in Lithuania. The concepts on disposal are constantly defined more precisely 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 costs assessment of geological repository installation was carried out and generic repository safety assessment was initiated.
In 2011 a great deal of attention was devoted to one of safety assessment aspects, the research of consistent patterns of gas migration from deep SNF repository. The amount of gas in the repository depends on the type of disposed waste and the selected conception of disposal. This research is performed together with 23 partners from 10 EU countries under the project Fate of Repository Gases (FORGE) (2009–2013) financed by the 7th Framework Programme (FP7) of the EU. In 2011 a model of gas migration from the repository was developed and initial numerical assessment was carried out applying PetraSim software package (the USA).
In 2011 a scientific project Probabilistic Uncertainty Assessment of Radiation Impact during the Analysis of NPP Dismantling and Radioactive Waste Managing (2010–2012) financed by the state budget grant was continued. The research on the radionuclide migration from deep SNF repository in case of container defect scenario is performed. The scenario assumes that a disposal container with a small defect (untightness) in its wall may pass the inspection by non-destructive control methods and be placed in the repository. Thus, radionuclide transport from disposal container through the wall defect is modelled. Having spread from the container, the radionuclides migrate through the bentonite layer (engineering barriers) and diffuse to the underground water, which flows in the fracture intersecting the tunnel in crystalline rocks.
During these investigations, the researchers are updating the model of radionuclide migration from RBMK-1500 SNF deep repository, developed in 2007–2009. They also aim at evaluating the influence of uncertainty, related to the increase of container wall defect, migration on the separate radionuclide from the container. In 2011, the influence of defect enlargement time and other parameter uncertainty on the assessment results of long-lived radionuclide 129I (T1/2 = 1.57×107 annually), 226Ra (T1/2 = 1.6×103 annually) migration was analysed. The probabilistic assessment of radionuclide transport demonstrated that aiming to optimize the analysis of radionuclide 129I transport through engineering barriers, it is worthwhile to target the further research on the parameters defining bentonite diffusion, instant release fraction and SNF matrix dissolution rate. Similarly, in the case of 226Ra the revision of the SNF matrix dissolution rate, bentonite sorption coefficient and the equivalent flow rate of underground water is recommended.
Furthermore, complex investigations of the influence of heat transfer and mechanical processes in natural and engineering barriers unsaturated with water were continued. Numerical research was carried out using software COMPASS (GRC, United Kingdom), whereas radionuclide migration was evaluated applying softwares AMBER (Quintessa, United Kingdom), Petrasim (USA), COMPULINK, CHAN3D, PREBAT-BATEMAN (SKB, Sweden).
In 2011, as a subcontractor to NUKEM Technologies GmbH (Germany), the Laboratory continued an extensive project Design and Installation of the Interim Storage Facility for RBMK Spent Nuclear Fuel Assemblies from Ignalina NPP Units 1 and 2 (2005–2011). This project comprises the analysis of all activities related with the design, construction, installation, commissioning, operation and decommissioning of the new SNF storage facility and the performance of all necessary works related to the SNF removal, packaging, sealing and transfer as well as operation of the appropriate equipment for implementation of chosen design concept. It is planned to store approximately 200 new type CONSTOR casks with intact and damaged SNF in the new storage facility.
The Laboratory prepares Environmental Impact Assessment and Safety Analysis Reports of this SNF storage facility (operational time no less than 50 years) and offers support in licensing the storage facility. In 2007, Environmental Impact Assessment Report was approved by the Ministry of Environment; in 2009, Preliminary Safety Analysis Report (PSAR) was prepared and agreed upon and the licence for construction of the new SNF storage facility was issued by VATESI. In 2010-2011, PSAR Addendum, which presents the evaluation of safety aspects of damaged RBMK-1500 nuclear fuel assemblies’ management and storage, was being prepared.
Safety of radioactive waste management
Since 1994 the Laboratory has been actively involved in the analysis of the radioactive waste management problems at Ignalina NPP. Laboratory experts together with the experts from SKB International (Sweden) carried out a number of projects, which included safety assessment of existing waste storage facilities and the possibilities to transform them into repositories. 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 preparing Safety Analysis Report, developed the database containing information on the radioactive waste, which is stored in the Maišiagala storage facility, and performed a comprehensive nuclide composition analysis. The Laboratory together with Framatome ANP GmbH (Germany) participated in executing the environmental impact and safety assessments for Ignalina NPP cement solidification facility and an interim solidified radioactive waste storage facility. Additionally, the Laboratory constantly participates in the research programmes coordinated by IAEA.
In recent years, a great deal of attention was devoted for the sitting of a new near-surface repository of radioactive waste in Lithuania, and for scientific research related to the radionuclide migration from radioactive waste repositories and its impact on safety. With the assistance of Swedish experts, the Laboratory specialists prepared the set of 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 waste activity distribution on radionuclide migration from model near-surface repository was investigated.
During 2006–2009, the Laboratory specialists 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; it was based on the possible engineering solutions of storage facility reconstruction into repository, components of disposal system. To be more precise, radioactive waste, storage facility and surface engineering barriers planned to be installed over storage facilities and site characteristics were taken into consideration.
In 2011, the Laboratory as subcontractor to NUKEM Technologies GmbH (Germany) continued the project New Ignalina NPP Solid Waste Management and Storage Facility (2006–2011). This facility is intended for solid radioactive waste retrieval, sorting, transportation, treatment (using envisaged technologies), packaging, characterisation and storage. The facility comprises the solid waste retrieval facility located at the existing INPP solid waste storage buildings, the new solid waste treatment facility, the new short-lived radioactive waste storage facility and the new long-lived radioactive waste long-term storage facility.
The Laboratory prepares environmental impact assessment and safety analysis reports for this complex. Environmental Impact Assessment Report was agreed upon and approved by the Ministry of Environment in 2008 and two PSARs, New Solid Waste Treatment and Storage Facilities at Ignalina NPP and New Solid Waste Retrieval Facility at Ignalina NPP were prepared. The former was approved in 2009 and VATESI issued the licence for the construction of the facility. Additionally, in 2009 two more PSARs, New Solid Waste Retrieval Facility. Retrieval Unit 1 and Retrieval Unit 2-3 at Ignalina NPP was newly prepared, while in 2010 both PSARs were submitted to authorities for review. The former was updated following the recommendations of the authorities and approved by VATESI in the end of 2010, while in the middle of 2011, the licence to build the complex was issued. The second PSAR was modified considering the recommendations of the authorities in 2011.
In 2010, the Laboratory, as a partner of Lithuanian consortium (JSC Specialus montažas–NTP, LEI, Pramprojektas, JSC Vilstata) continued implementing the project Installation of Very Low Level Radioactive Waste Repository (Landfill) (2008–2011). Landfill repository is intended for disposal of very low-level radioactive waste generated during Ignalina NPP operation and decommissioning. Landfill facility will be comprised of three repository modules and buffer storage where waste will be stored till their disposal. The Laboratory prepared Environmental Impact Assessment Report for the planned economic activity (approved by the Ministry of Environment in 2009) and two PSARs, The Buffer Storage of the Landfill Repository (approved by VATESI in 2009) and The Disposal Modules of the Landfill Repository (approved by VATESI in 2010). General Data Set on the Buffer Storage of the Landfill Repository was completed (approved by the European Commission in 2010), whereas in 2011 General Data Set on the Disposal Modules of the Landfill Repository was submitted to the European Commission for review.
Last year, the Laboratory together with partners from French companies AREVA TA and ANDRA and Lithuanian partners JSC Specialus montažas–NTP and Pramprojektas continued the project Low and Intermediate-Level Short-Lived Radioactive Waste Near-Surface Repository (Design) (2009–2012). The repository is intended for disposal of low and intermediate-level short-lived radioactive waste generated during Ignalina NPP operation and decommissioning.
In 2010-2011, the specialists of the Laboratory made a considerable contribution to the preparation of Design Concept Report, Waste Inventory Report and Site Revalidation Report which were submitted to the Contractor and approved. The results of exhaustive project implementation review were discussed in the meeting with the IAEA experts which took place in November 2011. Moreover, the preparatory work of technical design has already been initiated: the specialists of the Laboratory are going to assess the long-term safety of the planned repository and prepare the chapters on the preliminary safety analysis in the scope of technical design.
The Laboratory continued the previous research of radionuclides migration from near surface repositories. In 2011 in the scope of the scientific research project Probabilistic Uncertainty Assessment of Radiation Impact during the Analysis of NPP Dismantling and Radioactive Waste Managing (2010–2012) they analysed the migration of separate radionuclides from near-surface repositories in order to evaluate the factors which have the most influence on the uncertainty of the obtained results.
In 2011 during the implementation of the above-mentioned budgetary work Probabilistic Uncertainty Assessment of Radiation Impact during the Analysis of NPP Dismantling and Radioactive Waste Managing and the project Treatment and Disposal of Irradiated Graphite and Other Carbonaceous Waste (CARBOWASTE) (2008–2012) of the 7th Framework Programme of the EU, numerical research related to the radiological characterization of the constructional materials of RBMK-1500 reactor, namely irradiated graphite, was continued. In 2011, the modelling of axial neutron flux distribution was continued: the axial activity distributions of the main radionuclides in activated graphite were estimated, and the possible spread of their activity values was analysed regarding the amount of initial impurities. Having obtained the initial measurement results of the activity of several radionuclides in the reactor graphite sleeve of Ignalina NPP Unit 1, the calibration of the developed models was carried out. Similarly as before, the numerical research was performed using MCNP-5 (LANL, USA) and ORIGEN-S (from SCALE-5 software system) (ORNL, USA) software.
The feasibility study of RBMK-1500 graphite final disposal in a repository was analysed in the scope of CARBOWASTE project regarding the alternatives of treatment/non-treatment of the graphite. To assess the specificity of long-term repository operation after placing irradiated graphite, numerical models were developed. They were applied to evaluate the release of radionuclides from graphite and their transport through engineering barriers of the repository. The developed models of the repository environment were implemented using AMBER software (Quintessa, the United Kingdom). The analysis of radionuclide transport is carried out taking into account the results (on radionuclide release from waste, possible waste packaging, radionuclide inventory and activity of irradiated RBMK-1500 graphite, etc.) obtained in the scope of the mentioned project.
By implementing CARBOWASTE project in 2011, the researchers were also implementing Multi-Criteria Decision Analysis methodology. Having accumulated initial data on the physical, radiological, arrangement-scheme and other parameters of the equipment and carried out the initial analysis of the data. Alternative strategies of nuclear equipment dismantling were formulated. The analysis was carried out applying software DECRAD developed at LEI Nuclear Engineering Laboratory.
In 2011, the IAEA project Treatment Requirements for Irradiated RBMK-1500 Graphite to Meet Disposal Requirements (2010-2014) was initiated in cooperation with other countries. The research carried in the scope of this project by the researchers of the Laboratory is mostly related to meeting the disposal requirements for the treatment of irradiated RBMK-1500 graphite in Lithuania.
Evaluation of different factors related to decommissioning of nuclear power plants
In 2007–2010, Lithuanian Energy Institute, as a partner of consortium VT Nuclear Services Ltd (UK) – LEI – NUKEM (Germany), implemented the project Ignalina NPP Building 117/1 Equipment Decontamination and Dismantling. In 2009 the specialists of the Laboratory prepared Environmental Impact Assessment Report approved by the authorities, while in 2010 they completed General Data Set,made input to Basic Design and Safety Justification Report; the two latter were approved by the relevant authorities. The researchers of the Laboratory also participated in preparing the Detailed Design, which was reviewed and submitted to the contractor. Using CORA-CALCOM (NIS, Germany) software package, the equipment of building 117/1, waste amounts and their characteristics were analysed and economic assessment of the planned decontamination and dismantling activities was carried out. Following the prepared documentation, the INPP Dismantling and Decontamination Service, together with other divisions of the company, started the work of dismantling and decontamination of equipment installed in Building 117/1 on 1 December 2010 and completed them in October 2011.
In 2011, Lithuanian Energy Institute, as a partner of consortium Babcock (UK) – LEI – NUKEM Technologies GmbH (Germany), continued the project Ignalina NPP Building V1 Equipment Decontamination and Dismantling (2009–2011). In 2010 Specialists of the Laboratory completed General Data Set; in 2011 they prepared Environmental Impact Assessment Report and received its approval from the Ministry of Environment. At the end of 2011 Basic Design and Safety Justification Report were submitted to the authorities that are currently reviewing the documents. The preparation of the Detailed Design is going to be completed in 2012.
In 2009, the specialists of the Laboratory developed DECRAD software intended for analysis of decontamination and dismantling of nuclear power plants, planning the demand for expenses, costs and personnel, calculation of the personnel radiation doses, planning of radioactive waste disposal and the assessment of other parameters related to the decommissioning. The software may be applied for planning and analysing decommissioning of different power plants, their separate buildings or units. In 2011, the specialists upgraded and improved the software code DECRAD. It was successfully applied and is still used in the scope of the project Ignalina NPP Building V1 Equipment Decontamination and Dismantling.
In the scope of nuclear power plant shutdown projects, VISIPLAN 3D ALARA Planning Tool (SCK-CEN, Belgium) software is applied to estimate personnel radiation doses.
One of the most important tasks for the shutdown of NPP is safe dismantling of the equipment. Due to the shutdown Ignalina NPP Unit 1 in 2004 and Unit 2 in 2009, the analysis of the mentioned issues and suitable solutions are especially important. Apart from the already-mentioned specificities, in 2011 a probabilistic uncertainty assessment of radiation impact on the personnel dismantling the pipelines of the Ignalina NPP emergency cooling system was carried as a part of the project Probabilistic Uncertainty Assessment of Radiation Impact during the Analysis of NPP Dismantling and Radioactive Waste Managing (2010–2012).
Since 2002, the Laboratory has performed fire hazard assessments in the nuclear power plants and other important facilities. In consultation with Swedish experts, the Laboratory specialists assessed the fire hazard of Units 1 and 2 of Ignalina NPP. Fire hazard assessment of some renewed INPP rooms and newly designed INPP SNF and radioactive waste storage facilities were carried out as well. An external fire impact on the new INPP complex for solid waste treatment and storage was assessed and the fire hazard analysis of the most dangerous areas in the case of an internal fire was performed. In 2009, the impact of fire during the implementation of Ignalina 117/1 building dismantling and decontamination was evaluated as well as the fire safety of newly designed buffer storages and disposal units of Landfill repository was analysed. In 2011, the impact of fire during the implementation of Ignalina V1 unit dismantling and decontamination was assessed.
Research related to the construction of a new nuclear power plant in Lithuania and other international activity of the Laboratory
In 2007–2009, in consortium with Pöyry Energy Oy (Finland), the Laboratory specialists carried out the research related to the construction of new nuclear power plant in Lithuania. The Environmental Impact Assessment Programme for New Nuclear Power Plant and New Nuclear Power Plant Environmental Impact Assessment Report were prepared. In the EIA Report, possible environmental impacts of the construction and operation of 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 planed economic activity and, therefore, following this EIA Report, the Ministry of Environment has made a motivated decision on the construction possibilities of new nuclear power plant.
The researchers of the Laboratory continually participate in the research programmes coordinated by IAEA, namely Improvement of Safety Assessment Methodologies for Near Surface Disposal Facilities (ISAM) (1998–2001), Application of Safety Assessment Methodology for Near-Surface Waste Disposal Facilities (ASAM) (2002–2005), The Use of Numerical Models in Support of Site Characterization and Performance Assessment Studies of Geologic Repositories(2005–2010), Treatment of Irradiated Graphite to Meet Acceptance Criteria for Waste Disposal (2010–2014).
At the end of 2011, the researchers of the Laboratory in cooperation with 15 partners from 9 European countries initiated the 7FP project New MS Linking for an Advanced Cohesion in Euratom Research (NEWLANCER) (2011–2013). The main objective of the project is to analyse the research potential of EU new member States and promote scientific cooperation with the EU old member States. The project participants discussed project work packages, their implementation plans and schedule during the kick-off meeting, which took place in November 2011.
Together with 15 other organizations from the EU countries, Canada, the Netherlands and Sweden, LEI started the 7FP project Sustainable network of Independent Technical Expertise for radioactive waste disposal (SITEX) (2012–2014) in 2011. Its main objective is to identify efficient means to implement for the establishment of a European sustainable network of independent technical expertise in the field of radioactive waste disposal. It is intended for strengthening general and mutual understanding of different aspects regarding repository safety among the regulatory institutions and organizations providing technical safety expertise and waste management. The network also aims at assessing the demand for independent scientific research, recommendations for technical expertise, etc.
In 2011, the Laboratory (23 researchers) continued a state subsidy funded research work, carried out 12 applied research projects and earned more than 1 million LTL.
On 30 June 2011, the researcher of the Laboratory, Asta Narkūnienė, successfully defended her PhD thesis The Investigation of Radionuclide Release from the Hypothetical Repository for RBMK Spent Nuclear Fuel Disposal in the field of technology sciences, energetics and power engineering direction, and was granted a PhD degree. Audrius Šimonis joined the laboratory researchers also. He defended his PhD thesis Investigation of Personnel Exposure during Dismantling of Nuclear Facilities in the field of energetics and power engineering direction on 8 December 2011.
Researchers of the Laboratory were improving their qualification by actively participating in different training programmes and coordinating meetings. They presented 5 papers at international conferences (Sweden, Switzerland and Lithuania) and published 15 scientific articles in the Lithuanian and international journals.