A late agreement between China and Japan in the nu

A late "agreement" between China and Japan in the field of nuclear energy

on June 27, a late agreement between China and Japan in the field of nuclear energy reopened in Beijing

the nuclear power generation technology seminar originally scheduled to be held in Shenzhen in April this year by the China Nuclear Energy Industry Association and the Japan Federation of technologists and other Japanese institutions was postponed for nearly three months due to the impact of the Fukushima nuclear accident. Now the discussion content is expanded to nuclear power safety and technology, including the experience summary of the Fukushima nuclear accident, how to prevent disasters such as earthquakes and tsunamis, the aging management of nuclear power plants, and the rapid reactor High temperature gas cooled reactor and other new technologies

this is also the first face-to-face exchange between experts and scholars in the nuclear power industry between China and Japan after the IAEA international expert group submitted the report of the Japanese government on the Fukushima nuclear accident to the ministerial nuclear safety conference a few days ago

this seminar can enable us to further understand the occurrence, development and response of accidents from the two aspects of technology and management, on-site accident handling and public emergency response, and more deeply experience and understand the experience and lessons of accidents. Zhang Huazhu, chairman of the China Nuclear Energy Industry Association, said

ignoring the serious consequences caused by the tsunami

only improvements have been made in earthquake prevention. Relevant countermeasures for the tsunami have been studied, but they have been in the state of gradual discussion and improvement

when introducing the situation of the Fukushima nuclear power plant accident, Takemoto Congming, a senior consultant of Tokyo Electric Power Company (hereinafter referred to as TEPCO) and former deputy president of TEPCO, said that if the scale of the tsunami can be taken into account and existing technology can be used, disaster prevention planning and improvement can be completed at less cost. Although improvements have been made in earthquake preparedness based on the latest research results, tsunami countermeasures have been placed in the position of gradual discussion and improvement. The accident should be a lesson that the polymerization activity of epoxy monomer is significantly higher than that of carbon dioxide, and it also plays a role in deepening the understanding of the tsunami. Sakamoto smart said

according to Takemoto smart, the research on tsunami in Japan began in the 1970s, and the evaluation of tsunami has been conservative estimation and prediction based on historical data. In recent years, through some research, the evaluation of tsunami has entered a new stage. Since around 2000, a brand-new evaluation of tsunami has been made based on the numerical calculation of earthquake and tsunami that caused the tsunami and the water principle experiment. According to the relevant data, some scientific predictions have been made on the scale and probability of the tsunami. In 2007, TEPCO and Japan's atomic safety infrastructure Agency jointly completed a report on the risk of power failure and core melting caused by the tsunami. The analysis of the report at that time pointed out that the probability of core melting caused by a series of faults caused by the fracture of nuclear power plant pipelines was higher than that caused by internal reasons in the traditional sense

considering the impact of earthquake and tsunami, it is very inappropriate to place the power supply system in the lower part of the turbine plant. Sakamoto smart pointed out the key reason for the damage of the power supply system

it is understood that in this accident, the entire power system of internal combustion generators and related transmission and distribution devices of Fukushima 1 nuclear power plant, except unit 6, was built underground of the turbine building. Unit 1 was designed with reference to the mark of Ge in the United States in 960 (in the United States at that time, only the river bank and the east coast with less earthquakes were considered, and the impact of tsunami was hardly considered). Due to the small plant, the nuclear radiation suffered during regular inspection was high, and the operation was difficult. Therefore, from unit 6, the emergency internal combustion generator was placed in the reactor building

for TEPCO, Sakamoto smart believes that because TEPCO has not built and designed new nuclear power plants, its main business is to overhaul and maintain existing nuclear power plants. With regard to safety issues, especially the rapid technological progress, TEPCO gradually lost its keen sensitivity and observation, and was slow to respond to potential technical problems. He pointed out that for an enterprise, the investment in equipment and new technology is equally important compared with the stable operation of nuclear power plants, the utilization rate of equipment and the reduction of power generation costs

both multiplicity and diversity

nuclear power plants should adhere to diversity design based on multiplicity to avoid safety problems after multiple systems are damaged

on how to deal with the failure of emergency power supply, Nobuyuki Ueda, director of the safety committee of the Japanese atomic mechanics society, proposed that nuclear power plants should adhere to diversity design based on multiplicity to avoid safety problems after multiple systems are damaged. Multiplicity means that several sets of the same devices are set, and multiplicity means that machines and equipment with the same performance but different principles are equipped

take Douglas DC-10 aircraft as an example, if the floor at the boundary between the cabin and the cargo compartment is broken, the whole hydraulic control system will fail. However, for Boeing b-747, even if the above situation occurs, the other system on the top can still operate normally. In other words, this improvement of Boeing b-747 improves the reliability of aircraft safety system. Takeshi Ueda gives an example

in addition to analyzing the accident from a technical perspective, Nobuyuki Ueda mentioned how to explore reasonable suggestions from the lessons, including how to deal with tsunami prevention, power failure, total loss of cooling system, hydrogen explosion and other aspects in the short and medium term

with regard to the tsunami, he believed that in order to prevent important machine damage in safety in the short term, waterproof measures should be strengthened around the buildings equipped with main instruments; In the long run, the tsunami risk assessment method should be introduced to standardize and unify the impact of the tsunami. At the same time, a moisture barrier should be built around the nuclear power plant, and the risk of the tsunami washing away the equipment and buildings as a whole should be fully considered. We should also improve the waterproof performance of the interior of the building and establish waterproof routes for major components such as wires. In addition, it is necessary to reset the drainage pump and put all kinds of machine supplies away from the tsunami

as for the problem of power failure, Nobuyuki Ueda suggested that in the short term, it is necessary to ensure the power supply of various power sources such as power trucks and small generators, and set the scenario of complete loss of AC power to ensure the power supply of important machines and core monitoring systems, especially the power supply of valves after accidents. In addition, if multiple generators are set, connect the wires in advance. In the long run, it is necessary to modify the safety review guidelines and configure various power generation equipment such as steam turbines and generators in terms of equipment; In addition to seawater cooling, air-cooled generators should be prepared; It can also share power with other power stations, such as hydropower, or configure a small generator on the steam turbine driven core water injection pump to charge the battery for control

for the cooling system concerned by the industry, Nobuyuki Ueda pointed out that in addition to emergency cooling, it is also the most important and the longest time. However, spare parts such as seawater pump engines should be placed in places with minimal impact of the tsunami, and seawater pumps can also be equipped with waterproof facilities. Natural circulation without power and diversification of water sources can also be considered

the Fukushima nuclear accident did not negate the basic concepts of nuclear power plant safety such as multiple measures and deep protection. However, problems such as risk control or potential safety hazards that completely exceed the safety design standards at the emergence stage are highlighted due to the tsunami. In the future, we will carefully analyze the causes of accidents, including tsunamis, and reflect lessons and experiences into the design of existing light water reactors and new reactor types. Ueda stressed

aging management is imminent

nuclear reactors have no life span. Through appropriate management and technical improvement, the goal of long-term safe operation can be achieved

it is understood that Japan currently has 54 nuclear power plants, 2 of which are under construction and 12 of which are planned. Among the nuclear power plants, 19 have been in operation for more than 30 years, and 2 of the 19 have been in operation for more than 40 years (data before Fukushima 3/11 accident)

kajiro Mishima, director of the Japan Atomic Power Safety System Research Institute (Affiliated To Kansai Electric Power Company), said that in the long run, the possibility of building a new nuclear power plant in Japan is very small. One of the ways to supply electricity and reduce carbon dioxide emissions is to make the existing reactors operate for a long time, during which problems such as equipment aging and maintenance will be encountered; Or we can update and replace the equipment in the same nuclear power plant, which are two important issues facing Japan's nuclear power industry

the Japanese nuclear power industry generally believes that even nuclear power equipment and related instruments that have operated for a long time can achieve the goal of safe operation after technical evaluation, maintenance and proper management. Kajiro Mishima said that the operator of the nuclear power plant made a hypothetical judgment after 30 years of operation of the nuclear power plant, assuming 10. Working power supply: 220V ~ 240V nuclear power plant has operated for 60 years, how to improve the safety performance of relevant equipment and the technical requirements of non safety systems and buildings, and make a 60 year operation plan on this basis

relevant data show that in terms of unit aging management, Japan will put forward technical evaluation and improvement plans every 10 years for units that have operated for more than 30 years, but if problems are found in the annual regular inspection, they will also be dealt with in time. The United States puts forward relevant evaluation and improvement plans every 20 years for nuclear power plants that have operated for more than 40 years. France, Britain, Germany and Sweden have also proposed similar improvement plans to extend the operating life of nuclear power plants

it is understood that at present, Japan uses the national system to study the overall principle and mechanism of aging. For this purpose, it adopts more reliable technologies, such as state detection technology, and the research results will be reflected in the design of new reactors. In 2011, the government added 1.25 billion yen as the basic fund for aging research of nuclear power plants, but due to the Fukushima nuclear accident, the basic fund will be 900million yen. How to take the Fukushima nuclear accident as an opportunity to establish a new research system will be an issue for Japan to explore in the future. Said Ichiro Mishima

for the purpose of aging research, kajiro Mishima explained that it is to form a concept that nuclear reactors have no life, and long-term safe operation can be achieved through appropriate management and technical improvement