In 2007, the license for the second reactor unit of the Ignalina nuclear power plant was renewed considering the safety-related modifications introduced in this reactor.The Safety Analysis Report for this reactor unit...In 2007, the license for the second reactor unit of the Ignalina nuclear power plant was renewed considering the safety-related modifications introduced in this reactor.The Safety Analysis Report for this reactor unit was prepared with more strict criteria. The bounding reactivityinitiated accident(RIA) performed by the Lithuanian Energy Institute could be mentioned as an example. The performed analysis demonstrated that even when the worst initial conditions and possible uncertainties are considered,the fuel cladding remains intact. However, the analysis was performed assuming a fresh fuel assembly. In this study, an analysis of the fuel rod cladding behavior in the RBMK-1500 reactor following a bounding RIA is performed using the computational codes FEMAXI-6 and RELAP5. The analysis is extended by modeling an oxide layer(nodular corrosion) on the external surface cladding. An uncertainty and sensitivity analysis was performed using a method developed by the Society for Plant and Reactor Safety,employing the Software for Uncertainty and Sensitivity Analyses, in order to evaluate the effect of the oxide layer on the inside and outside fuel rod temperatures. The results of the thermo-mechanical analysis(stress, strain, and enthalpy) for a local oxide layer with a thickness of 70μm show that despite the exceeded limit of allowed linear power density, the fuel rod is under acceptable safety conditions.展开更多
Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems （LACANES）, the Institute for Neutron Physics and Reactor Technology takes part in the validatio...Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems （LACANES）, the Institute for Neutron Physics and Reactor Technology takes part in the validation process of system codes and the characterization of the thermal-hydraulic behavior of an experimental loop operated with liquid lead-bismuth-eutectics. To confirm the calculations, the results were compared to experimental data obtained from the HELIOS facility at the Seoul National University and to the results of other benchmark participants. The comparison showed that the calculations are within measurement tolerance but nevertheless discrepancies among the participants exist. The pressure drop estimation is determined by a variety of empirical correlations for the friction and the form loss coefficients. Hence, uncertainty and sensitivity measures were applied to find out which parameter is more relevant for the overall pressure drop. In the frame of this investigation, the system code TRACE and the software system for uncertainty and sensitivity, SUSA, were used. The results show that the total pressure drop varies between -30 and ＋15% related to the reference case.展开更多
Fungi that are barely lichenized or non-lichenized and closely related to lichenized taxa,the so-called borderline fungi,are an important element in reconstructing the evolutionary history of lichenized lineages.Artho...Fungi that are barely lichenized or non-lichenized and closely related to lichenized taxa,the so-called borderline fungi,are an important element in reconstructing the evolutionary history of lichenized lineages.Arthoniaceae is a prime example including non-lichenized,saprotrophic lineages which potentially were precursors to lichenized taxa.In this study,we focused on saprotrophic species of Arthonia sensu lato,including new sequence data for Arthonia pinastri.We obtained fresh material of this taxon from a living branch of Fraxinus ornus in Italy to assess its taxonomic status and to elucidate its phylogenetic relationships within Arthonia.Thin sections of the thallus and ascomata of A.pinastri confirmed the absence of a photobiont.Maximum likelihood and Bayesian analyses of combined mtSSU,nuLSU and RPB2 sequence data placed the species close to A.dispersa(barely lichenized or non-lichenized)and A.punctiformis(non-lichenized)in a clade closely related to Arthonia sensu stricto,and the A.pinastri clade is here resurrected under the name Naevia.Ancestral character state analysis within a broader context of Arthoniales does not support the saprotrophic lifestyle to be a plesiomorphic feature,but suggests loss of lichenization in Naevia,as well as loss and possible regain in a second clade containing saprotrophic species and including taxa resembling Mycoporum,underlining the evolutionary plasticity of Arthoniales.These two clades constitute model taxa to further investigate the evolution of alternative biological lifestyles within the context of chiefly lichenized taxa.展开更多
文摘In 2007, the license for the second reactor unit of the Ignalina nuclear power plant was renewed considering the safety-related modifications introduced in this reactor.The Safety Analysis Report for this reactor unit was prepared with more strict criteria. The bounding reactivityinitiated accident(RIA) performed by the Lithuanian Energy Institute could be mentioned as an example. The performed analysis demonstrated that even when the worst initial conditions and possible uncertainties are considered,the fuel cladding remains intact. However, the analysis was performed assuming a fresh fuel assembly. In this study, an analysis of the fuel rod cladding behavior in the RBMK-1500 reactor following a bounding RIA is performed using the computational codes FEMAXI-6 and RELAP5. The analysis is extended by modeling an oxide layer(nodular corrosion) on the external surface cladding. An uncertainty and sensitivity analysis was performed using a method developed by the Society for Plant and Reactor Safety,employing the Software for Uncertainty and Sensitivity Analyses, in order to evaluate the effect of the oxide layer on the inside and outside fuel rod temperatures. The results of the thermo-mechanical analysis(stress, strain, and enthalpy) for a local oxide layer with a thickness of 70μm show that despite the exceeded limit of allowed linear power density, the fuel rod is under acceptable safety conditions.
文摘Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems （LACANES）, the Institute for Neutron Physics and Reactor Technology takes part in the validation process of system codes and the characterization of the thermal-hydraulic behavior of an experimental loop operated with liquid lead-bismuth-eutectics. To confirm the calculations, the results were compared to experimental data obtained from the HELIOS facility at the Seoul National University and to the results of other benchmark participants. The comparison showed that the calculations are within measurement tolerance but nevertheless discrepancies among the participants exist. The pressure drop estimation is determined by a variety of empirical correlations for the friction and the form loss coefficients. Hence, uncertainty and sensitivity measures were applied to find out which parameter is more relevant for the overall pressure drop. In the frame of this investigation, the system code TRACE and the software system for uncertainty and sensitivity, SUSA, were used. The results show that the total pressure drop varies between -30 and ＋15% related to the reference case.
基金We thank the Thailand Research Fund(“The future of specialist fungi in a changing climate:baseline data for generalist and specialist fungi associated with ants,Rhododendron species and Dracaena species DBG6080013”and“Impact of climate change on fungal diversity and biogeography in the Greater Mekong Subregion RDG6130001”)“The 2019 high-end foreign expert introduction plan to Kunming Institute of Botany(granted by the Ministry of Science and Technology of the People’s Republic of China(Grant Number G20190139006))for funding this research.S.C.Karunarathna would like to thank the CAS President’s International Fellowship Initiative(PIFI)under the following grant:2018PC0006 and the National Science Foundation of China(NSFC,project code 31851110759)+1 种基金We also thank Udeni Jayalal,Nalin Wijayawardene,Ming-Ying Zhang,Mohammed Warris,Lee B.G and Eleni Gentekaki for their support during this research.Dhanushka Wanasinghe would like to thank CAS President’s International Fellowship Initiative(PIFI)for funding his postdoctoral research(Number 2019PC0008)the National Science Foundation of China and the Chinese Academy of Sciences for financial support under the following Grants:41761144055,41771063 and Y4ZK111B01.We also extend our gratitude to Teuvo Ahti,David Hawksworth,Pier-Luigi Nimis and Rikard Sundin and Mats Wedin who helped to clarify the nomenclatural status of the genus Naevia.
文摘Fungi that are barely lichenized or non-lichenized and closely related to lichenized taxa,the so-called borderline fungi,are an important element in reconstructing the evolutionary history of lichenized lineages.Arthoniaceae is a prime example including non-lichenized,saprotrophic lineages which potentially were precursors to lichenized taxa.In this study,we focused on saprotrophic species of Arthonia sensu lato,including new sequence data for Arthonia pinastri.We obtained fresh material of this taxon from a living branch of Fraxinus ornus in Italy to assess its taxonomic status and to elucidate its phylogenetic relationships within Arthonia.Thin sections of the thallus and ascomata of A.pinastri confirmed the absence of a photobiont.Maximum likelihood and Bayesian analyses of combined mtSSU,nuLSU and RPB2 sequence data placed the species close to A.dispersa(barely lichenized or non-lichenized)and A.punctiformis(non-lichenized)in a clade closely related to Arthonia sensu stricto,and the A.pinastri clade is here resurrected under the name Naevia.Ancestral character state analysis within a broader context of Arthoniales does not support the saprotrophic lifestyle to be a plesiomorphic feature,but suggests loss of lichenization in Naevia,as well as loss and possible regain in a second clade containing saprotrophic species and including taxa resembling Mycoporum,underlining the evolutionary plasticity of Arthoniales.These two clades constitute model taxa to further investigate the evolution of alternative biological lifestyles within the context of chiefly lichenized taxa.
