• experimental investigation of heat transfer and turbulent transport in single-phase flows: 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 and turbulent transport in single-phase flows in various channels and geological structures;

• management of spent nuclear fuel: modelling of fuel characteristics, safety and environmental impact assessment of storage and disposal facilities, normative and legislative base;

• management of radioactive waste: 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 assessment 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.

 

 

The Laboratory has a comprehensive experience in investigations of heat transfer and flow hydrodynamics in different components of energy facilities, whereas in recent years in geological structures and shafts as well. It has been observed that in many energy facilities the impact of thermogravitational forces is manifested in cases of laminar and turbulent flows. Under certain conditions the impact evoked by thermogravitational forces on heat transfer usually becomes a reason for accidents in different facilities. Thus mixed convection scientific research has been begun since 1985 in the Laboratory (originally in pipes, later in flat channels as well).

 

 

 

In 2008 experimental and numerical investigations in vertical flat channel in transitional flow region were continued. The results of experimental and numerical investigations in transitional flow zone for aiding and opposing flows were analysed and correlated. Numerical modeling under different cases of mixed convection was carried out applying FLUENT (USA) code. Obtained heat transfer and flow hydrodynamics results in case of mixed convection for opposing flows fundamentally change the understanding concerning the laminar flow transition to the turbulent under the impact of thermogravitational forces.

 

 

Specialists of the Laboratory for a number of years have been performing scientific research related with management and disposal of spent nuclear fuel (further SNF). The dry interim storage facility for SNF at Ignalina NPP with CASTOR RBMK-1500 and CONSTOR RBMK-1500 type casks was commissioned in 1999. The Laboratory has been performing studies related to the safety assessment of SNF storage and disposal. The Laboratory carried out criticality assessments for the casks of normal and extended capacity with fresh and burned-up nuclear fuel under normal operational and accident conditions, variation of radioactive nuclides activity during the interim storage period, radiation doses on the cask surface and at the specific distance from it, and temperatures of the cask.

 

Implementing research on SNF disposal in Lithuania, the Laboratory experts with the assistance of Swedish experts proposed the generic concepts of deep geological repository in clay and in crystal rocks in Lithuania. The concepts on disposal are constantly revised and optimised taking into account international experience and physical, chemical, thermal and mechanical properties of a specific repository site. While analysing possibilities of SNF disposal in Lithuania, the costs assessment of geological repository installation was carried out and generic repository safety assessment was initiated.

 

In 2008 research related to radionuclides migration and processes influencing it in the far field of the repository (geosphere) were continued aiming at more optimally evaluating the impact of geosphere on the safety of SNF repository. Research was carried out with the researchers from other countries (the coordinator – IAEA). Data of Veresnia site (Ukraine) was used. Evaluating different flow conditions of underground water in different geological formations, the geofiltration nature of underground water under respective conditions was determined. Preliminary results of numerical evaluation revealed that under given conditions the unsorbed long-lived iodine isotope 129I dispersed from repository near field environment would reach the river water, however its flow would be 10 times smaller than the flow via the engineering barriers. Whereas the biggest flow values achievement times differ approximately 49 times. This means that radionuclides need time to reach the river water thus they are delayed in geosphere.

 

Complex researches of the impact of heat and gas dispersion on radionuclides transfer were continued. COMPULINK, CHAN3D, PREBAT-BATEMAN (Sweden), AMBER (UK), and TOUGH2 (USA) codes were applied for the assessment of radionuclides migration.

 

In 2008 the Laboratory together with GNS-RWE NUKEM GmbH (Germany) consortium continued the project – The Interim Storage Facility for RBMK Spent Nuclear Fuel Assemblies from Ignalina NPP Units 1 and 2 Supply and Installation (2005–2009). 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 2008 Environmental Impact Assessment Report was approved by the Ministry of Environment and Preliminary Safety Analysis Report was submitted to relevant parties for review.

 

 

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, including safety evaluation of existing waste storage facilities. Long-term safety assessment of existing radioactive waste storage facilities at Ignalina NPP and Maišiagala was performed, and the possibilities to transform these storage facilities into repositories were analysed. The Laboratory together with Framatome ANP GmbH (Germany) participated in environmental impact and safety assessments for Ignalina NPP cement solidification facility and a temporary solidified radioactive waste storage facility. The Laboratory constantly participates in IAEA coordinated research programmes.

 

In recent years a lot of attention was paid to site selection for a radioactive waste near surface repository in Lithuania, also to scientific research related with radionuclides migration from radioactive waste repositories and their influence on safety. The Laboratory specialists with the assistance of Swedish experts prepared the set of criteria for choosing a near surface repository site, improved the concept of a near surface repository project, and prepared the implementation programme. The impact of heterogeneous waste activity distribution on radionuclides migration from model surface repository was investigated.

 

 

 

 

Together with French companies Thales Engineering and Consulting and ANDRA as well as 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 all information on the radioactive waste inventory, which is being stored in the Maišiagala storage facility, and performed a comprehensive nuclide composition analysis.

 

Implementing the investigation, funded by Science and Study fund, the Laboratory specialists together with the Institute of Physics prepared the report Research on Radioactive Waste Generation, Radionuclides Migration and Impact to Environment and Public. DUST, GENII, GWSCREEN (USA), AMBER codes were used for the investigation.

 

In 2008 the Laboratory specialists continued to implement 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 performed. In the research possible engineering solutions of storage facility reconstruction into repository, components of disposal system, i.e. radioactive waste, storage facility and surface engineering barriers planned to be installed over storage facilities and site characteristics were considered. ISAM safety analysis method, AMBER and DUST codes were used in the assessment. Prepared documents were submitted to regulatory institutions in 2007, whereas in 2008 they were coordinated.

 

In 2008 the Laboratory together with NUKEM GmbH (Germany) continued the project New Ignalina NPP Solid Waste Management and Storage Complex (2006–2009). The Laboratory prepares environmental impact and safety analysis reports for this complex. In 2008 Environmental Impact Assessment Report was approved by the Ministry of Environment, whereas two preliminary safety analysis reports: Ignalina NPP New Solid Waste Management and Storage Complex and Ignalina NPP New Solid Waste Unloading Complex were submitted to regulatory institutions for review.

 

In 2008 the Laboratory as partner of Lithuanian consortium (JSC Specialus montažas–NTP, LEI, PramProjektas, JSC Vilstata) started to implement a new project Installation of Very Low-level Radioactive Waste Repository (Landfill). Landfill repository is designed for disposal of very low-level radioactive waste, generated during Ignalina NPP operation and decommissioning. Landfill complex 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 (common for buffer storage and disposal modules) and Safety Analysis Report (for buffer storage) and prepared documents were submitted for review to regulatory institutions.

 

 

In 1998 the Laboratory specialists started a new activity related to the planning of decommissioning of Ignalina NPP. Our experts participated in PHARE project preparing Preliminary Ignalina NPP Decommissioning Plan. An extensive database describing the characteristics of the elements of different systems and DEC-RAD software was developed. This software enables to estimate the amount of radioactive waste, which will be accumulated at Ignalina NPP, and also costs for carrying out the presumable operations. In the course of preparing Final Ignalina NPP Decommissioning Plan, this code was further developed at the Laboratory and information on radiological and technical data on Ignalina NPP systems was updated. In order to evaluate radioactive contamination level of the most contaminated systems, LLWAA-DECOM (Belgium) code adjusted to RBMK reactors was used. In 2004 the Laboratory specialists for the Ministry of Economy prepared the drafts on The Ignalina NPP Decommissioning Programme and the Plan of Means of its Implementation for the period 2005–2009.

 

The fire hazard analysis for Ignalina NPP Unit 1 and Unit 2 was carried out together with Swedish experts. Fire hazard assessment of newly designed Ignalina NPP SNF storage facility was carried out as well. In 2008 fire hazard analysis was carried out while preparing for Decontamination and Dismantling of Facilities of Ignalina NPP Building 117/1.

 

Since 2002 the Laboratory has been participating in IAEA coordinated research project Disposal Aspects of Low and Intermediate Level Decommissioning Waste. The Laboratory performed radioactive deposits formation analysis, also analysed the expected amounts of the radioactive waste at final INPP shutdown. Radioactive residue composition and their activity assessment methodology during the final reactor shutdown was prepared, forecasted quantities of radioactive waste were estimated, preliminary specific activity values for radioactive waste packages with activated reactor components were calculated.

 

 

In 2008 research concerning neutron activation of reactor constructions was continued, most of attention giving to reactor constructional elements, other than graphite stack boundary. In order to evaluate the activation of such elements, neutron flows should be simulated using numerical method in the constructions since in RBMK reactors neutron flux are measured only in the boundaries of reactor graphite stack. Thus the methodology is developed, which enables to estimate neutron flux in the analysed reactor constructions. MCNP-5, SCALE (USA) codes were used for the modelling of neutron flux.

 

Together with Institute of Physics the Laboratory implemented the project Development of Radiological Characterization Programme for Equipment and Installations at INPP. General Programme of Radiological Survey was prepared and approved by regulatory institutions. Historical Assessment Report of Radiological Situation at INPP and Programmes of Detail Radiological Characterizations of Individual Ignalina NPP Units (V1, G1, 117/1) were prepared as well.

 

In 2008 new project – Preparation of Detail Radiological Survey Programmes for Ignalina NPP Blocks B1, D0, D1 and Building No 119 Facilities has been started. Microsoft Access database was developed, where all data, necessary for describing equipment and schemes with planned positions of radioactivity measurement and sample taking, will be accumulated. Developed codes and collected and analysed data regarding radiological situation at Ignalina NPP are necessary for preparation of the Ignalina NPP Unit 1 dismantling projects.

 

In 2008 Lithuanian Energy Institute, as a partner of consortium BNG (UK)-LEI-NUKEM (Germany), participated in the new project – Decontamination and Dismantling of Facilities of Ignalina NPP Building No 117/1. Researchers of the Laboratory participate in preparing environmental impact assessment and safety justification reports, technical and detailed projects and developing General Data Set.

 

Using CORA/CALCOM (Germany) code, the equipment of building 117/1, waste amounts and their characteristics were analysed and assessment of cost of deactivation and dismantling activities was carried out. Personnel radiation doses were simulated after estimating surface contamination of facilities by VISIPLAN 3D ALARA (Belgium). In 2008 Environmental Impact Report and Safety Justification Report and General Data Set were prepared and submitted to the Ignalina NPP for review.

 

 

In 2008 researchers of the Laboratory started the activities related with the implementation of new nuclear power plant in Lithuania. Consortium Pöyry Energy Oy (Finland)-LEI (Lithuania) completed important project Preparation of Environmental Impact Assessment Programme for New Nuclear Power Plant, where the scope of new nuclear power plant environmental impact assessment report was determined. In Environmental impact assessment report, in cooperation with specialists and experts from Finish and Lithuanian institutions (Institute of Botany, Institute of Ecology, National Public Healthcare Laboratory), deterministic and probabilistic environmental impacts during new NPP construction and operation were estimated. Applying numerical methods and experience while operating Ignalina NPP it was analysed how planned economy activity may impact the following environment components – water, air, soil, biological diversity and public health. A great deal of attention was devoted to numerical simulations of Drūkšiai lake water temperature and radionuclides dispersion, to estimate impact on lake ecosystem and to estimate radiological impact of public health during normal operation as well as during design basis and severe accident. Since planned economy activity may have intercontinental impact, it was estimated how new NPP may impact Latvian and Belarus environment components.