As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has...As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has been accumulated mainly in marine sediments, because sea is about 80% of planet surface, and solid fission products released by nuclear explosions are transported by wind first and then by rain to liquid and solid portions on earth, while gaseous fission products are diffused in the atmosphere. In this way, heavy, high yielding fission products, such as 137Cs, get marine sediments, where they are found mixed with heavy radioactive natural elements such as U, Th and their also radioactive decay products. But since alkaline are so abundant on earth, it is also found natural radioactive isotope 4~K, 0.0118% of isotopes forming K element, with half life 1.28 ~ l09, in the time range of planet age and elements origin. So, one easy way to assess both the importance and evaluation of radioactive contamination at global scale should be to establish a RCF （radioactive contamination factor） as a percentage of 137Cs contaminant radioactivity in marine sediments, compared to 4~K natural radioactivity present from the very beginning of earth, both expressed as Bq per gram of sediment. In the frame of these rather general considerations, a research project has started in Mexico whose varied purposes are： to characterize sea regions in both vast littorals in the country, by its natural 4~K radioactivity present in sea salts, as well as to determine if 137Cs traces produced by recent radioactive contamination have reached their coasts. Also, to assess the 137Cs traces already present in marine sediments as a result of more than two thousand nuclear test explosions performed till now, rather than contamination produced by four main accidents in nuclear reactors during the last 60 years. It is proposed a radioactive contamination factor obtained from samples taken up in both coasts during the last two years, which should be very useful in two ways： first to assess the real danger of radioactive contamination already present by comparing with natural radioactivity, and second to assess the growth, equilibrium or drop of radioactive contamination, given that nuclear energy is still the best option to solve the large energy demand foreseen in the near future.展开更多
Technology we used in order to tell visual stories is constantly improving, newer technology superseding the old one at a breathtaking rate. Yet, video technology is a means and does not do the storytelling itself. Ho...Technology we used in order to tell visual stories is constantly improving, newer technology superseding the old one at a breathtaking rate. Yet, video technology is a means and does not do the storytelling itself. However, visual storytellers must keep themselves updated with technology in order to get the best of their work. DSLR cameras are now leading the visual storytelling pack and some respected visual storytellers share conclusions of their experiences.展开更多
Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing...Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing the anti-accident technical measures, improving the installation and debugging level, and strengthening operation inspection, are proposed.展开更多
Reaction runaway has longtime been an issue in chemical industry as it often leads to severe accidents if not controlled and inhibited properly.Herein we have reviewed several key considerations and procedures to prev...Reaction runaway has longtime been an issue in chemical industry as it often leads to severe accidents if not controlled and inhibited properly.Herein we have reviewed several key considerations and procedures to prevent such phenomena,including inherently safer reactor design,thermal risk assessment and early warning detection of runaway,and pointed out that the basic principle underlying is necessary heat management and construction of resilient processes.For inherently safer reactor design,important factors such as heat removal,heat capacitance,flow behaviors and explosive behaviors have been investigated.The survey shows that heat exchanger(HEX) reactor and microreactor outperform traditional reactors.Meanwhile,we have looked into the effect of thermal risk ranking and safety operation region determining for thermal risk assessment,and the influence of runaway criteria and construction methods for early detection of reaction runaway as well.It shows that thermal risk assessment plays a key role on process design,and early warning detection system(EWDS) is preferable on prevention of reaction runaway.In the end,perspectives regarding inherently safer designs with the measures discussed above have been provided.展开更多
The QUENCH experimental programme at Karlsruhe under severe accident conditions, but while the geometry is still Institute of Technology investigates heat-up and reflooding of a core mainly rod-like. The recent QUENCH...The QUENCH experimental programme at Karlsruhe under severe accident conditions, but while the geometry is still Institute of Technology investigates heat-up and reflooding of a core mainly rod-like. The recent QUENCH-ACM series of experiments, comprising QUENCH-12 （El 10 cladding alloy）, -14 （M5 alloy） and -15 （Zirlo^TM alloy）, together with QUENCH-06 （reference case, Zircaloy-4 alloy） addressed the effect of alternative cladding materials on oxidation and quenching under similar conditions. Superficial inspection of the experimental results reveals only minor differences in the thermal and oxidation response, except for the much larger hydrogen release during reflood in QUENCH-12. Post-test calculations were performed using a version of SCDAP/RELAP5/MOD3.2, modified to represent the QUENCH facility and to invoke alternative oxidation correlations. The calculations agreed rather well with experiments QUENCH-06, -14 and -15, but the significant hydrogen release during reflood in QUENCH-12 was not captured. Closer examination of the experimental results reveals further differences between QUENCH-12 which may be linked to breakaway oxidation of the E110 cladding. The analyses support the heuristic observation that there was no major difference between the influence of Zircaloy-4, M5 or ZirloTM, but the E-110 exhibited a contrasting behaviour with a consequent impact on the reflooding.展开更多
The purpose of this study was to assess the effects of reducing driving fatigue with magnitopuncture stimuli on Dazhui (DU14) point and Neiguan (PC6) points using heart rate (HR), reaction time (RT) testing, critical ...The purpose of this study was to assess the effects of reducing driving fatigue with magnitopuncture stimuli on Dazhui (DU14) point and Neiguan (PC6) points using heart rate (HR), reaction time (RT) testing, critical flicker fusion frequency (CFF) and subjective evaluation. Twenty healthy subjects were randomly divided into two groups: A-group (study group) and B-group (control group). All subjects were required to be well rested before the experiment. The subjects were engaged in high speed driving at a constant vehicle velocity of 80 km/h continuously for three hours on a test course simulating an expressway. During the driving magnitopunctures were applied to the Dazhui (DU14) point and Neiguan (PC6) points for the A-group when the subject performed the task for two and half hours, and for the B-group magnitopunctures were applied to non-acupuncture points at the same time session. In this study RT exbited a significant delay in B-group (P<0.01) but no found in A-group after the driving task. CFF and subjective evaluation also exhibited significant differences between the two groups after the driving task (P<0.05). The findings showed that magnitopuncture stimuli on Dazhui (DU14) point and Neiguan (PC6) points could reduce the effects of driving fatigue.展开更多
During the course of a hypothetical severe accident in a nuclear Pressurized Water Reactor （PWR）, containment reactor is pressurized by steam and hydrogen released from a primary circuit breach and distributed into ...During the course of a hypothetical severe accident in a nuclear Pressurized Water Reactor （PWR）, containment reactor is pressurized by steam and hydrogen released from a primary circuit breach and distributed into the containment according to convective flows and steam wall condensation. In addition, core degradation leads to fission products released into the containment. Water spraying is used in the containment as mitigation means in order to reduce pressure, to remove fission products and to enhance the gas mixing in case of presence of hydrogen. This paper presents results of the TOSQAN aerosol program undertaken by the Institute de Radioprotection et de Sfiret6 Nucl6aire （IRSN） devoted to study the aerosol removal by a spray, for typical accidental thermal hydraulic conditions in PWR containment. The TOSQAN facility is a large enclosure devoted to simulate typical accidental thermal hydraulic flow conditions in nuclear PWR containment.展开更多
In a severe accident of a light water reactor, ablation of the RPV （reactor pressure vessel） lower head by corium is a key phenomenon, which affects progression of the accident. The MPS （moving particle semi-impli...In a severe accident of a light water reactor, ablation of the RPV （reactor pressure vessel） lower head by corium is a key phenomenon, which affects progression of the accident. The MPS （moving particle semi-implicit） method is one of particle methods that calculate behavior of incompressible fluid by semi-implicit method. In preceding studies, the MPS method has been extensively studied and developed for simulations of different phenomena involved in severe accident of nuclear reactors. This paper aims to investigate whether the MPS method is capable of analyzing the lower head ablation phenomenon. The small-scale experiment carried out at CRIEPI （Central Research Institute of Electric Power Industry） using Pb-Bi vessel and silicone oil was analyzed for the validation of the MPS method. The MPS analysis well reproduced the experimental phenomena qualitatively. However, with respect to some quantitative results, more investigation such as influence of the calculation particle size is necessary.展开更多
The 5MW low temperature nuclear heating reactor (NHR-5) is a new and advanced type of nuclear reactor developed by Institute of Nuclear Energy Technology (INET) of Tsinghua University of China in 1989. Its main loop i...The 5MW low temperature nuclear heating reactor (NHR-5) is a new and advanced type of nuclear reactor developed by Institute of Nuclear Energy Technology (INET) of Tsinghua University of China in 1989. Its main loop is a thermal-hydraulic system with natural circulation. This paper studies the safety of NHR under the condition of loss-of-coolant accidents (LOCAs) by means of simulant experiments. First, the background and necessity of the experiments are presented, then the experimental system, including the thermal-hydraulic system and the data collection system, and similarity criteria are introduced. UP to now, the discharge experiments with the residual heating power (20% rated heating power) have been carried out on the experimental system. The system parameters including circulation flow rate, system pressure, system temperature, void fraction, discharge mass and so on have been recorded and analyzed. Based on the results of the experiments, the conclusions are shown as folios: on the whole, the reactor is safe under the condition of LOCAs, but the thermal vacillations resulting from the vibration of the circulation flow rate are disadvantageous to the internal parts of the reactor core.展开更多
文摘As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has been accumulated mainly in marine sediments, because sea is about 80% of planet surface, and solid fission products released by nuclear explosions are transported by wind first and then by rain to liquid and solid portions on earth, while gaseous fission products are diffused in the atmosphere. In this way, heavy, high yielding fission products, such as 137Cs, get marine sediments, where they are found mixed with heavy radioactive natural elements such as U, Th and their also radioactive decay products. But since alkaline are so abundant on earth, it is also found natural radioactive isotope 4~K, 0.0118% of isotopes forming K element, with half life 1.28 ~ l09, in the time range of planet age and elements origin. So, one easy way to assess both the importance and evaluation of radioactive contamination at global scale should be to establish a RCF （radioactive contamination factor） as a percentage of 137Cs contaminant radioactivity in marine sediments, compared to 4~K natural radioactivity present from the very beginning of earth, both expressed as Bq per gram of sediment. In the frame of these rather general considerations, a research project has started in Mexico whose varied purposes are： to characterize sea regions in both vast littorals in the country, by its natural 4~K radioactivity present in sea salts, as well as to determine if 137Cs traces produced by recent radioactive contamination have reached their coasts. Also, to assess the 137Cs traces already present in marine sediments as a result of more than two thousand nuclear test explosions performed till now, rather than contamination produced by four main accidents in nuclear reactors during the last 60 years. It is proposed a radioactive contamination factor obtained from samples taken up in both coasts during the last two years, which should be very useful in two ways： first to assess the real danger of radioactive contamination already present by comparing with natural radioactivity, and second to assess the growth, equilibrium or drop of radioactive contamination, given that nuclear energy is still the best option to solve the large energy demand foreseen in the near future.
文摘Technology we used in order to tell visual stories is constantly improving, newer technology superseding the old one at a breathtaking rate. Yet, video technology is a means and does not do the storytelling itself. However, visual storytellers must keep themselves updated with technology in order to get the best of their work. DSLR cameras are now leading the visual storytelling pack and some respected visual storytellers share conclusions of their experiences.
文摘Considering the actual operating experience of the Daode Wind Farm, this paper analyzes the rea-sons for the fault of the lO-kV switch cabinet. Some technical improvements and management measures, such as implementing the anti-accident technical measures, improving the installation and debugging level, and strengthening operation inspection, are proposed.
基金Supported by the National Key Research and Development Program of China(2016YFB0301701)
文摘Reaction runaway has longtime been an issue in chemical industry as it often leads to severe accidents if not controlled and inhibited properly.Herein we have reviewed several key considerations and procedures to prevent such phenomena,including inherently safer reactor design,thermal risk assessment and early warning detection of runaway,and pointed out that the basic principle underlying is necessary heat management and construction of resilient processes.For inherently safer reactor design,important factors such as heat removal,heat capacitance,flow behaviors and explosive behaviors have been investigated.The survey shows that heat exchanger(HEX) reactor and microreactor outperform traditional reactors.Meanwhile,we have looked into the effect of thermal risk ranking and safety operation region determining for thermal risk assessment,and the influence of runaway criteria and construction methods for early detection of reaction runaway as well.It shows that thermal risk assessment plays a key role on process design,and early warning detection system(EWDS) is preferable on prevention of reaction runaway.In the end,perspectives regarding inherently safer designs with the measures discussed above have been provided.
文摘The QUENCH experimental programme at Karlsruhe under severe accident conditions, but while the geometry is still Institute of Technology investigates heat-up and reflooding of a core mainly rod-like. The recent QUENCH-ACM series of experiments, comprising QUENCH-12 （El 10 cladding alloy）, -14 （M5 alloy） and -15 （Zirlo^TM alloy）, together with QUENCH-06 （reference case, Zircaloy-4 alloy） addressed the effect of alternative cladding materials on oxidation and quenching under similar conditions. Superficial inspection of the experimental results reveals only minor differences in the thermal and oxidation response, except for the much larger hydrogen release during reflood in QUENCH-12. Post-test calculations were performed using a version of SCDAP/RELAP5/MOD3.2, modified to represent the QUENCH facility and to invoke alternative oxidation correlations. The calculations agreed rather well with experiments QUENCH-06, -14 and -15, but the significant hydrogen release during reflood in QUENCH-12 was not captured. Closer examination of the experimental results reveals further differences between QUENCH-12 which may be linked to breakaway oxidation of the E110 cladding. The analyses support the heuristic observation that there was no major difference between the influence of Zircaloy-4, M5 or ZirloTM, but the E-110 exhibited a contrasting behaviour with a consequent impact on the reflooding.
文摘The purpose of this study was to assess the effects of reducing driving fatigue with magnitopuncture stimuli on Dazhui (DU14) point and Neiguan (PC6) points using heart rate (HR), reaction time (RT) testing, critical flicker fusion frequency (CFF) and subjective evaluation. Twenty healthy subjects were randomly divided into two groups: A-group (study group) and B-group (control group). All subjects were required to be well rested before the experiment. The subjects were engaged in high speed driving at a constant vehicle velocity of 80 km/h continuously for three hours on a test course simulating an expressway. During the driving magnitopunctures were applied to the Dazhui (DU14) point and Neiguan (PC6) points for the A-group when the subject performed the task for two and half hours, and for the B-group magnitopunctures were applied to non-acupuncture points at the same time session. In this study RT exbited a significant delay in B-group (P<0.01) but no found in A-group after the driving task. CFF and subjective evaluation also exhibited significant differences between the two groups after the driving task (P<0.05). The findings showed that magnitopuncture stimuli on Dazhui (DU14) point and Neiguan (PC6) points could reduce the effects of driving fatigue.
文摘During the course of a hypothetical severe accident in a nuclear Pressurized Water Reactor （PWR）, containment reactor is pressurized by steam and hydrogen released from a primary circuit breach and distributed into the containment according to convective flows and steam wall condensation. In addition, core degradation leads to fission products released into the containment. Water spraying is used in the containment as mitigation means in order to reduce pressure, to remove fission products and to enhance the gas mixing in case of presence of hydrogen. This paper presents results of the TOSQAN aerosol program undertaken by the Institute de Radioprotection et de Sfiret6 Nucl6aire （IRSN） devoted to study the aerosol removal by a spray, for typical accidental thermal hydraulic conditions in PWR containment. The TOSQAN facility is a large enclosure devoted to simulate typical accidental thermal hydraulic flow conditions in nuclear PWR containment.
文摘In a severe accident of a light water reactor, ablation of the RPV （reactor pressure vessel） lower head by corium is a key phenomenon, which affects progression of the accident. The MPS （moving particle semi-implicit） method is one of particle methods that calculate behavior of incompressible fluid by semi-implicit method. In preceding studies, the MPS method has been extensively studied and developed for simulations of different phenomena involved in severe accident of nuclear reactors. This paper aims to investigate whether the MPS method is capable of analyzing the lower head ablation phenomenon. The small-scale experiment carried out at CRIEPI （Central Research Institute of Electric Power Industry） using Pb-Bi vessel and silicone oil was analyzed for the validation of the MPS method. The MPS analysis well reproduced the experimental phenomena qualitatively. However, with respect to some quantitative results, more investigation such as influence of the calculation particle size is necessary.
文摘The 5MW low temperature nuclear heating reactor (NHR-5) is a new and advanced type of nuclear reactor developed by Institute of Nuclear Energy Technology (INET) of Tsinghua University of China in 1989. Its main loop is a thermal-hydraulic system with natural circulation. This paper studies the safety of NHR under the condition of loss-of-coolant accidents (LOCAs) by means of simulant experiments. First, the background and necessity of the experiments are presented, then the experimental system, including the thermal-hydraulic system and the data collection system, and similarity criteria are introduced. UP to now, the discharge experiments with the residual heating power (20% rated heating power) have been carried out on the experimental system. The system parameters including circulation flow rate, system pressure, system temperature, void fraction, discharge mass and so on have been recorded and analyzed. Based on the results of the experiments, the conclusions are shown as folios: on the whole, the reactor is safe under the condition of LOCAs, but the thermal vacillations resulting from the vibration of the circulation flow rate are disadvantageous to the internal parts of the reactor core.
