The benchmark analysis of unintended simultaneous opening of three main steam relief valves, whic... more The benchmark analysis of unintended simultaneous opening of three main steam relief valves, which occurred at Ignalina nuclear power plant unit I on November 26 in 1986, is performed. Such an event is a beyond design basis event for the RBMK-1500 (Large Channel Type Water-cooled Graphite-moderated Reactor). The analysis performed is employing the code CONTAIN, version C11AF. The CONTAIN code is used for the prediction of thermohydraulic parameters in the accident localization system. The water backflow from the lower condensing pools to the bottom steam reception chamber and further water distribution to neighboring cells is well predicted. Nevertheless, the lack of the measured data does not allow to perform a more detailed analysis of the event. In this paper the accident localization system of Ignalina NPP, event description, results of the analysis, lessons learnt and open questions of the analysis are presented.
In the case of a severe accident in a water-cooled nuclear power plant large amounts of hydrogen ... more In the case of a severe accident in a water-cooled nuclear power plant large amounts of hydrogen could be generated due to fuel claddings oxidation and released to the containment. At certain concentrations of steam air and hydrogen the hydrogen combustion could occur and challenge the structural integrity of the containment, which is a last barrier preventing from radioactive material release to the environment. Therefore, a detailed knowledge of containment thermal-hydraulics is necessary to predict the local distribution of hydrogen, steam and air inside the containment. This paper presents the experience of Lithuanian Energy Institute in simulation of the experiments performed in MISTRA test facility for the case of the International Standard Problem ISP47. The MISTRA facility is located in the Saclay center of France Atomic Energy Commissariat (CEA) and is related to the research of containment thermal-hydraulics and hydrogen safety. The MISTRA facility and its operating condit...
Science and Technology of Nuclear Installations, 2015
The decommissioning of nuclear facilities requires adequate planning and demonstration that disma... more The decommissioning of nuclear facilities requires adequate planning and demonstration that dismantling and decontamination activities can be conducted safely. Existing safety standards require that an appropriate safety assessment be performed to support the decommissioning plan for each facility (International Atomic Energy Agency, 2006). This paper presents safety assessment approach used in Lithuania during the development of the first dismantling and decontamination project for Ignalina NPP. The paper will mainly focus on the identification and assessment of the hazards raised due to dismantling and decontamination activities at Ignalina Nuclear Power Plant and on the assessment of the nonradiological and radiological consequences of the indicated most dangerous initiating event. The drop of heavy item was indicated as one of most dangerous initiating events for the discussed Ignalina Nuclear Power Plant dismantling and decontamination project. For the analysis of the nonradiol...
The release of radioactive materials to the environment is of special importance in the case of a... more The release of radioactive materials to the environment is of special importance in the case of any accident at Nuclear Power Plants (NPP). The integrated analysis of thermal-hydraulic parameters behavior and radioactive fission products (FP) transport and deposition in the compartments play an important role in the evaluation of FP release to the environment and determines the irradiation dozes of personnel and public. In this report the transport and the deposition of radioactive material in the Ignalina NPP unit 1 compartments as well as the FP source term to the environment in the case of design basis loss-of-coolant accidents are discussed. The calculation models for the evaluation of FP transport and deposition as well as the results of performed calculations of several accidents at Ignalina NPP are presented. 1
ABSTRACT One of the main tasks of any decommissioning project is the licensing process, which all... more ABSTRACT One of the main tasks of any decommissioning project is the licensing process, which allows implementation of developed strategies in the real nuclear power plant. The Lithuanian laws on nuclear energy and radioactive waste management require that dismantling and decontamination projects shall be licensed by the Lithuanian State Nuclear Power Safety Inspectorate and other Authorities. Licensing is an inseparable part of the Lithuanian regulatory and supervisory system for safety of nuclear facilities. The licensing process starts when the nuclear power plant submits the first licensing document(s) to the Authorities. Usually the licensing documents cover Basic Design, Safety Assessment, Environmental Impact Assessment and Civil Design reports. Safety Assessment Report is a major document, which justifies that the proposed activities will be implemented in compliance with design and regulatory requirements. Licensing process is completed when all the licensing documents are approved by the Authorities and authorization to start dismantling and decontamination activities is received by the nuclear power plant.
Abstract Even though research of severe accidents in light water reactors is performed around the... more Abstract Even though research of severe accidents in light water reactors is performed around the world for several decades many questions remain. Research is mostly performed for vessel-type reactors. RBMK is a channel type light water reactor, which differs from the vessel-type reactors in several aspects. These differences impose some specifics in the accident phenomena and processes that occur during severe accidents. Severe accident research for RBMK reactors is taking first steps and very little information is available in the open literature. The existing severe accident analysis codes are developed for vessel-type reactors and their application to the analysis of accidents in RBMK is not straightforward. This paper presents the results of an analysis of large loss-of-coolant accident scenarios with loss of coolant injection to the core of RBMK-1500. The analysis performed considers processes in the reactor core, in the reactor cooling system and in the confinement until the fuel melting started. This paper does not aim to answer all the questions regarding severe accidents in RBMK but rather to start a discussion, identify the expected timing of the key phenomena.
The purpose of this article is to determine the heat transfer and hydraulic drag in thin annular ... more The purpose of this article is to determine the heat transfer and hydraulic drag in thin annular pebble beds with axial gas flow and investigate the flow distribution along annular pebble beds with radial flow. The experimental investigations showed that in thin annular pebble beds heat transfer values, equal to those for large (unlimited) pebble beds, could be achieved. The
Kol buvo eksploatuojama Ignalinos AE, daugelis Lietuvos energetikos instituto (LEI) Branduolinių ... more Kol buvo eksploatuojama Ignalinos AE, daugelis Lietuvos energetikos instituto (LEI) Branduolinių įrenginių saugos laboratorijos (BĮSL) mokslinių tyrimų buvo nukreipta branduolinių elektrinių saugos klausimams spręsti. Nuo 2006 m. LEI įsitraukė į mokslinius tyrimus, susijusius su branduolių sintezės tematika. Branduolių sintezė – tai procesas, kurio metu susijungia du lengvi branduoliai, pavyzdžiui, vandenilio izotopai deuteris ir tritis, sudarydami naują helio branduolį, o šio proceso metu išsiskiria milžiniškas energijos kiekis. Toks procesas vyksta ir žvaigždėse, o pasaulio mokslininkai sprendžia, kaip jį būtų galima suvaldyti ir pritaikyti Žemėje. Jei 2006 m. LEI vykdė tik nedidelį projektą, susijusį su vienu iš ITER reaktoriaus saugos aspektų, tai vėliau LEI BĮSL mokslininkai plėtė savo veiklos apimtis ir įsitraukė į naujas tyrimų sritis: neutronų pernašos procesų tyrimai, įrangos patikimumo tyrimai, įvairių konstrukcijų struktūrinio vientisumo tyrimai, t. t. Jau 2013 m. kartu s...
The experimental results of the thermal hydraulic characteristics of pebble beds and bundles of t... more The experimental results of the thermal hydraulic characteristics of pebble beds and bundles of twisted oval rods is an issue of high importance in the designing of effective heat exchangers, modular gas-cooled or low-capacity mobile nuclear reactors, in chemical and other industries. This paper concentrates on the test sections made up of axially streamlined cylinders with two kinds of a filling in a space between cylinders pebble bed or bundles of twisted oval rods. Two types of pebble beds, as well as two types of bundles of twisted rods, were investigated in order to find the influence of different packing on the flow mixing and hydraulic drag. The flow mixing factors were computed by comparing the calculated and measured temperature distributions produced by a heat spot in the bed. The drag coefficient of the pebble bed with a regular rhombic structure was measured to be 2.6-3 times higher than that of the random pebble bed. The mixing factors in the case of the randomly packed...
Experimental results on the determination of porosity, hydraulic-drag, and heat transfer coeffici... more Experimental results on the determination of porosity, hydraulic-drag, and heat transfer coefficients of spheres packed in narrow annuli are described. The annuli simulates annular fuel rods for nuclear reactor
This paper describes drag and mixing in composite beds made up of bundles of longitudinal cylinde... more This paper describes drag and mixing in composite beds made up of bundles of longitudinal cylinders arranged in a triangular pattern, with the space between them filled with plastic beads either arranged into an ordered rhomboidal packing, or dumped in to produce a random packing. The airflow through the bed was axial. The mixing factors were computed by comparing the predicted and the measured temperature distributions produced by a heat spot in the bed
Abstract Decommissioning of nuclear facilities involves different types of activities, tools, equ... more Abstract Decommissioning of nuclear facilities involves different types of activities, tools, equipment and systems. There is a potential for a wide range of radiological and industrial accidents during various stages of a decommissioning project creating risk for workers and the environment. The occurrence of accidents is possible due to many different operations involving movement and handling of large pieces of equipment and contaminated items. In addition, size reduction and decontamination processes are capable of producing hazards. One of the first steps in developing a safety assessment for decommissioning activities is the identification of hazards that can affect workers, members of the public and the environment during decommissioning activities, and then to identify engineered and administrative control measures to prevent, eliminate or mitigate the hazards and their consequences. Fault and hazard identification can be undertaken in several ways using a range of tools and techniques, including Hazard and Operability Study (HAZOP). The paper will mainly focus on the application of HAZOP technique for identification of the hazards raised due to dismantling and decontamination activities at the Ignalina NPP, as well as at feasibility study for the management of Bohunice V1 NPP primary circuit components.
The benchmark analysis of unintended simultaneous opening of three main steam relief valves, whic... more The benchmark analysis of unintended simultaneous opening of three main steam relief valves, which occurred at Ignalina nuclear power plant unit I on November 26 in 1986, is performed. Such an event is a beyond design basis event for the RBMK-1500 (Large Channel Type Water-cooled Graphite-moderated Reactor). The analysis performed is employing the code CONTAIN, version C11AF. The CONTAIN code is used for the prediction of thermohydraulic parameters in the accident localization system. The water backflow from the lower condensing pools to the bottom steam reception chamber and further water distribution to neighboring cells is well predicted. Nevertheless, the lack of the measured data does not allow to perform a more detailed analysis of the event. In this paper the accident localization system of Ignalina NPP, event description, results of the analysis, lessons learnt and open questions of the analysis are presented.
In the case of a severe accident in a water-cooled nuclear power plant large amounts of hydrogen ... more In the case of a severe accident in a water-cooled nuclear power plant large amounts of hydrogen could be generated due to fuel claddings oxidation and released to the containment. At certain concentrations of steam air and hydrogen the hydrogen combustion could occur and challenge the structural integrity of the containment, which is a last barrier preventing from radioactive material release to the environment. Therefore, a detailed knowledge of containment thermal-hydraulics is necessary to predict the local distribution of hydrogen, steam and air inside the containment. This paper presents the experience of Lithuanian Energy Institute in simulation of the experiments performed in MISTRA test facility for the case of the International Standard Problem ISP47. The MISTRA facility is located in the Saclay center of France Atomic Energy Commissariat (CEA) and is related to the research of containment thermal-hydraulics and hydrogen safety. The MISTRA facility and its operating condit...
Science and Technology of Nuclear Installations, 2015
The decommissioning of nuclear facilities requires adequate planning and demonstration that disma... more The decommissioning of nuclear facilities requires adequate planning and demonstration that dismantling and decontamination activities can be conducted safely. Existing safety standards require that an appropriate safety assessment be performed to support the decommissioning plan for each facility (International Atomic Energy Agency, 2006). This paper presents safety assessment approach used in Lithuania during the development of the first dismantling and decontamination project for Ignalina NPP. The paper will mainly focus on the identification and assessment of the hazards raised due to dismantling and decontamination activities at Ignalina Nuclear Power Plant and on the assessment of the nonradiological and radiological consequences of the indicated most dangerous initiating event. The drop of heavy item was indicated as one of most dangerous initiating events for the discussed Ignalina Nuclear Power Plant dismantling and decontamination project. For the analysis of the nonradiol...
The release of radioactive materials to the environment is of special importance in the case of a... more The release of radioactive materials to the environment is of special importance in the case of any accident at Nuclear Power Plants (NPP). The integrated analysis of thermal-hydraulic parameters behavior and radioactive fission products (FP) transport and deposition in the compartments play an important role in the evaluation of FP release to the environment and determines the irradiation dozes of personnel and public. In this report the transport and the deposition of radioactive material in the Ignalina NPP unit 1 compartments as well as the FP source term to the environment in the case of design basis loss-of-coolant accidents are discussed. The calculation models for the evaluation of FP transport and deposition as well as the results of performed calculations of several accidents at Ignalina NPP are presented. 1
ABSTRACT One of the main tasks of any decommissioning project is the licensing process, which all... more ABSTRACT One of the main tasks of any decommissioning project is the licensing process, which allows implementation of developed strategies in the real nuclear power plant. The Lithuanian laws on nuclear energy and radioactive waste management require that dismantling and decontamination projects shall be licensed by the Lithuanian State Nuclear Power Safety Inspectorate and other Authorities. Licensing is an inseparable part of the Lithuanian regulatory and supervisory system for safety of nuclear facilities. The licensing process starts when the nuclear power plant submits the first licensing document(s) to the Authorities. Usually the licensing documents cover Basic Design, Safety Assessment, Environmental Impact Assessment and Civil Design reports. Safety Assessment Report is a major document, which justifies that the proposed activities will be implemented in compliance with design and regulatory requirements. Licensing process is completed when all the licensing documents are approved by the Authorities and authorization to start dismantling and decontamination activities is received by the nuclear power plant.
Abstract Even though research of severe accidents in light water reactors is performed around the... more Abstract Even though research of severe accidents in light water reactors is performed around the world for several decades many questions remain. Research is mostly performed for vessel-type reactors. RBMK is a channel type light water reactor, which differs from the vessel-type reactors in several aspects. These differences impose some specifics in the accident phenomena and processes that occur during severe accidents. Severe accident research for RBMK reactors is taking first steps and very little information is available in the open literature. The existing severe accident analysis codes are developed for vessel-type reactors and their application to the analysis of accidents in RBMK is not straightforward. This paper presents the results of an analysis of large loss-of-coolant accident scenarios with loss of coolant injection to the core of RBMK-1500. The analysis performed considers processes in the reactor core, in the reactor cooling system and in the confinement until the fuel melting started. This paper does not aim to answer all the questions regarding severe accidents in RBMK but rather to start a discussion, identify the expected timing of the key phenomena.
The purpose of this article is to determine the heat transfer and hydraulic drag in thin annular ... more The purpose of this article is to determine the heat transfer and hydraulic drag in thin annular pebble beds with axial gas flow and investigate the flow distribution along annular pebble beds with radial flow. The experimental investigations showed that in thin annular pebble beds heat transfer values, equal to those for large (unlimited) pebble beds, could be achieved. The
Kol buvo eksploatuojama Ignalinos AE, daugelis Lietuvos energetikos instituto (LEI) Branduolinių ... more Kol buvo eksploatuojama Ignalinos AE, daugelis Lietuvos energetikos instituto (LEI) Branduolinių įrenginių saugos laboratorijos (BĮSL) mokslinių tyrimų buvo nukreipta branduolinių elektrinių saugos klausimams spręsti. Nuo 2006 m. LEI įsitraukė į mokslinius tyrimus, susijusius su branduolių sintezės tematika. Branduolių sintezė – tai procesas, kurio metu susijungia du lengvi branduoliai, pavyzdžiui, vandenilio izotopai deuteris ir tritis, sudarydami naują helio branduolį, o šio proceso metu išsiskiria milžiniškas energijos kiekis. Toks procesas vyksta ir žvaigždėse, o pasaulio mokslininkai sprendžia, kaip jį būtų galima suvaldyti ir pritaikyti Žemėje. Jei 2006 m. LEI vykdė tik nedidelį projektą, susijusį su vienu iš ITER reaktoriaus saugos aspektų, tai vėliau LEI BĮSL mokslininkai plėtė savo veiklos apimtis ir įsitraukė į naujas tyrimų sritis: neutronų pernašos procesų tyrimai, įrangos patikimumo tyrimai, įvairių konstrukcijų struktūrinio vientisumo tyrimai, t. t. Jau 2013 m. kartu s...
The experimental results of the thermal hydraulic characteristics of pebble beds and bundles of t... more The experimental results of the thermal hydraulic characteristics of pebble beds and bundles of twisted oval rods is an issue of high importance in the designing of effective heat exchangers, modular gas-cooled or low-capacity mobile nuclear reactors, in chemical and other industries. This paper concentrates on the test sections made up of axially streamlined cylinders with two kinds of a filling in a space between cylinders pebble bed or bundles of twisted oval rods. Two types of pebble beds, as well as two types of bundles of twisted rods, were investigated in order to find the influence of different packing on the flow mixing and hydraulic drag. The flow mixing factors were computed by comparing the calculated and measured temperature distributions produced by a heat spot in the bed. The drag coefficient of the pebble bed with a regular rhombic structure was measured to be 2.6-3 times higher than that of the random pebble bed. The mixing factors in the case of the randomly packed...
Experimental results on the determination of porosity, hydraulic-drag, and heat transfer coeffici... more Experimental results on the determination of porosity, hydraulic-drag, and heat transfer coefficients of spheres packed in narrow annuli are described. The annuli simulates annular fuel rods for nuclear reactor
This paper describes drag and mixing in composite beds made up of bundles of longitudinal cylinde... more This paper describes drag and mixing in composite beds made up of bundles of longitudinal cylinders arranged in a triangular pattern, with the space between them filled with plastic beads either arranged into an ordered rhomboidal packing, or dumped in to produce a random packing. The airflow through the bed was axial. The mixing factors were computed by comparing the predicted and the measured temperature distributions produced by a heat spot in the bed
Abstract Decommissioning of nuclear facilities involves different types of activities, tools, equ... more Abstract Decommissioning of nuclear facilities involves different types of activities, tools, equipment and systems. There is a potential for a wide range of radiological and industrial accidents during various stages of a decommissioning project creating risk for workers and the environment. The occurrence of accidents is possible due to many different operations involving movement and handling of large pieces of equipment and contaminated items. In addition, size reduction and decontamination processes are capable of producing hazards. One of the first steps in developing a safety assessment for decommissioning activities is the identification of hazards that can affect workers, members of the public and the environment during decommissioning activities, and then to identify engineered and administrative control measures to prevent, eliminate or mitigate the hazards and their consequences. Fault and hazard identification can be undertaken in several ways using a range of tools and techniques, including Hazard and Operability Study (HAZOP). The paper will mainly focus on the application of HAZOP technique for identification of the hazards raised due to dismantling and decontamination activities at the Ignalina NPP, as well as at feasibility study for the management of Bohunice V1 NPP primary circuit components.
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