There is a reason for the nuclear leakage in Japan.
After the earthquake in Japan on March 1 1, a hydrogen explosion occurred in the nuclear power unit of Fukushima Daiichi nuclear power plant in Japan, and the control failed. At present, the worst case may be that 1 and Unit 3 failed to inject water, and the nuclear fuel overflowed through the containment after melting, resulting in nuclear leakage.
"Even in the worst case, the amount of spilled nuclear radiation will not be too large. First, the reactor has been shut down before, and second, the uranium material used for nuclear power is only 3%-5%, which is far lower than the 95% abundance of nuclear bombs. In addition, the evacuation and dilution of seawater and wind have little impact on China. " Zhao Yamin, a researcher at the Nuclear and Radiation Safety Center of the National Nuclear Safety Administration, said in an interview with this reporter that the Japanese nuclear accident has highlighted many weaknesses in nuclear power safety worldwide.
Nuclear power generation in Japan began in the 1960s. According to the latest statistics released by the International Atomic Energy Agency, since 19631October 26th, the first experimental nuclear power plant was built in Shaolin Temple Village, Ibaraki Prefecture, Japan has 54 nuclear power plants. At present, Japan's nuclear power generation capacity ranks third in the world after the United States and France.
In May 2006, the Department of Resources and Energy of the Ministry of Economy, Trade and Industry of Japan formulated a medium-and long-term outline of the National Nuclear Power Plan aimed at promoting the utilization of nuclear energy and ensuring energy supply. The proportion of nuclear energy in Japan's overall energy structure has greatly increased, and it has become one of the most important energy sources in Japan. At present, about 30% of Japan's electricity supply is provided by nuclear power.
Judging from the Fukushima nuclear power plant where the accident occurred, many nuclear power plants in Japan were started in the 1970s, and most of the equipment belonged to the second-generation nuclear power model at that time, and the seismic grade at the time of construction was only about 7.
After the completion of these nuclear power plants, many accidents occurred. After entering 2 1 century, its nuclear accidents have become more intensive and frequent.
"The aging technology, insufficient fortification against earthquake magnitude and insufficient consideration of the concurrent factors of multiple natural disasters are the most fundamental reasons for this nuclear accident, but the enlightenment of this accident does not stop there." Zhao Yamin believes that there are many important issues worthy of consideration by all nuclear power workers.
According to Zhao Yamin, the first thing is to reconsider the emergency of power loss caused by waste heat. Waste heat management mainly includes safe cleaning, waste heat output and water cooling. Japan has done a good job in accident cleaning, but after the shutdown, the power supply stopped and the external power supply was lost, which led to the continuous evaporation of waste heat, and the hydrogen explosion exposed the reactor core, and then radioactive substances were brought out through artificial pressure relief and hydrogen explosion.
"Then there is water shortage, because the reactors of nuclear power plants can't use seawater, but use deionized water to reduce corrosion. However, after the tsunami, the supply of deionized water was obviously insufficient, and even the supply of fresh water was insufficient. Finally, seawater was injected, but after seawater injection, more than 90% of nuclear power plants will be scrapped. " Zhao Yamin said that after the earthquake, the reactor was shut down safely, but then there was a tsunami and a new water injection problem, so the safety of the accident should be considered many times in the future. "Don't just consider the nuclear issue from the ideal situation. If the problem is particularly ideal and there is an unexpected situation, the treatment will become blind. "
The dilemma of global nuclear power retention and abolition
Facing the nuclear power crisis in Japan, the attitudes of governments to the development direction of nuclear power are quite different, and different camps have also been derived. Germany has made it clear that it will accelerate its withdrawal from nuclear power, while the United States, France and Russia have all indicated that they will not waver in their determination to develop nuclear power.
In fact, the different attitudes of heads of state towards nuclear power development are closely related to the development of electric power in various countries. According to the latest data released by the International Atomic Energy Agency in June 5438+ 10 this year, there are currently 442 nuclear power units in operation in the world, and the nuclear power generation accounts for about 16% of the global total power generation.
Among them, the number of power stations is US 104, France 58, Japan 54 and Germany 17. Among the four countries, the United States has the most nuclear power plants and Germany has the least. The weight of nuclear power generation is about 20% in the United States, 80% in France, 30% in Japan and only 23% in Germany. Judging from the number of nuclear power plants and the proportion of power generation, it is obvious that the United States and France rely on nuclear power.
Moreover, from the cost point of view, the cost of nuclear power in all countries is slightly lower than the local on-grid tariff, so from the practical point of view, nuclear power has obvious advantages over other new energy sources.
However, this advantage seems to be only the long board of wooden barrels, and the safety problem is still the fatal resistance to the development of nuclear power in the world.
The development of global nuclear power began in the 1950s. With 1954, the former Soviet Union built the world's first nuclear power plant, and the United States and other countries quickly followed suit. After entering the 1960s, nuclear power developed on the expressway. At that time, a new nuclear power plant was put into operation every 17 days on average. It is at this construction frequency that during the 20 years from 1960 to 1980, 242 nuclear power units were put into operation in the world.
Because of the shortage of oil at that time, the economy of nuclear power was enlarged, and the second generation pressurized water reactor, boiling water reactor and graphite reactor and pressurized water reactor built by the Soviet Union began to form export scale. Among them, Japan and France introduced and digested the technology of pressurized water reactor and boiling water reactor in the United States, and the equipment of Fukushima nuclear power plant in Japan also originated from this period.
However, the accident at Three Mile Island Nuclear Power Station and the Chernobyl nuclear leak sounded a safety alarm for the development of nuclear power, and the safety and economy of nuclear power began to be reassessed worldwide, and the approval of nuclear power in various countries was tightened. The data show that from 1990s to 2004, the annual growth rate of global total installed nuclear power capacity dropped from the previous 17% to 2%, and the development of nuclear power entered a stage of stagnation and slowdown.
With the global energy crisis and the improvement of nuclear power technology, nuclear power has been revived after entering 2 1 century, and countries have begun to rebuild nuclear power plants.
As an energy expert interviewed by a reporter said, the transitional role of nuclear power is irreplaceable in the period when traditional energy is further exhausted, wind power and photoelectricity are still unstable and prices are high.
On the one hand, it is the worldwide risk caused by nuclear leakage of nuclear power plants, on the other hand, it is the energy transition support function and low power generation cost of nuclear power plants. Between giving up and acquiring, the survival or abolition of nuclear power will remain a world problem in the long run.
China's nuclear power: It should be taken into account.
Worst result
Compared with Germany, the United States and other developed countries, the latest attitude of nuclear power development in China is to stop approval and adjust planning.
By the end of 20 10, the installed capacity of nuclear power in China is only 1080000 kilowatts, accounting for only 1. 12% of the total installed capacity, which is far from the goal of 4% in the medium and long-term planning.
According to the new energy development plan disclosed by the National Energy Administration, the installed capacity of nuclear power will reach 49 million kilowatts by 20 15, and 70-80 million kilowatts by 2020, accounting for more than 5% of the total installed capacity. By then, the proportion of nuclear power in primary energy will reach about 4%, that is, nearly 4% of 15% non-fossil energy consumption will be composed of nuclear power.
From 108,000 kilowatts to 80 million kilowatts, and from 1. 12% to more than 5%, the leap of these figures requires China to launch nuclear power projects quickly and on a large scale in the next10 year. Based on this calculation, on average, more than 8 new units need to be built every year to complete the target plan.
Since 2005, the state has successively approved Liaoning Hongyanhe and other 13 nuclear power projects. At present, there are 0/3 units in operation in China, and 28 units under construction, with 30.97 million kilowatts, accounting for more than 40% of the world total.
"Previous nuclear power plant accidents were all caused by human error, but this Japanese nuclear accident was caused by an earthquake and a tsunami at the same time, which provided us with a new research topic. Under the combined influence of unknown and unpredictable multiple disasters, how should we prevent them? In this regard, the experience of the whole world is zero. " Geological expert Qin told reporters.
Li Yan, manager of Greenpeace Climate and Energy Project, also said that although the risk of earthquakes in coastal areas of China is not as high as that in Japan, the environmental risk is very complicated due to frequent natural disasters in China, so the worst result should be considered in the construction of nuclear power plants.
At present, the site selection of nuclear power plants in China mainly adopts weighted scoring method, which includes four categories *** 18, namely, the actual situation around, the impact on organisms, the impact on residents and the feasibility of implementing emergency plans. Among them, the weight factor of earthquake probability and intensity is 2, accounting for 6% of the total weight.
According to our site selection regulations, there will be a regional demonstration and an engineering demonstration for the earthquake resistance of nuclear power plants. For the regionality of the site, we should consider several hundred square kilometers to see if there are any large fault zones and active faults, and then listen to the opinions of seismologists. Then, according to the earthquake intensity table of China, the earthquake intensity and grade of the address are obtained, and then the nuclear power plant is upgraded to one level to ensure that the reactor can be safely cleaned and the main nuclear equipment will not be damaged when an earthquake occurs in this area.
"If there are frequent earthquakes in this place and the intensity is high, we will definitely not approve it." Zhao Yamin told this reporter.
In addition, many experts interviewed by reporters said that the storage of nuclear waste should also attract enough attention. At present, there are three main ways to treat nuclear waste: one is that spent fuel is treated to produce high-level radioactive waste liquid, which is transformed into glass blocks with relatively stable physical and chemical properties through solidification process; The second is to build an underground repository and bury the spent fuel directly in the reliable rock stratum below 500 meters; The third is through separation and evolution, recycling and reuse.
"One kind of solid waste is low-level radioactive waste, which will eventually be disposed of by the regional repository, and the other is spent fuel, which will be sent to the national geological repository for disposal. If there is an earthquake and the nuclear power plant is shut down, radioactive waste must be properly managed. The underground repository is currently only available in the United States, and 20 17 will be put into use. " According to Zhao Yamin, the storage life of low-level radioactive waste is 300-500 years, while the storage life of high-level radioactive waste needs 654.38+10,000-300,000 years. "How to properly keep it for such a long time and always be vigilant has put forward very high quality requirements for people engaged in nuclear power."
Not only nuclear waste disposal, but once China starts the plan of rapid development of nuclear power, the demand for nuclear power professionals will suddenly increase in a short time. "If the personnel training can't keep up, it is necessary to dilute the technicians of the original nuclear power plant and transfer them to support the construction of another nuclear power plant. Once an accident happens, it will be difficult to deal with. " Yuan Zhushu, a professor of nuclear science and technology at Fudan University, said.
"In an emergency, people's first reaction is often a mistake, but accidents in nuclear power plants are often sudden, which requires nuclear construction personnel to have good quality and be trained and retrained. In the event of an emergency, they can calm down and will not aggravate the expansion of the accident because of human error. " Zhao Yamin said.
In addition, the development of nuclear power in China started late, and most of the models currently used are pressurized water reactors and some heavy water reactors. However, the PWR units in China are mainly the second generation units and the second generation improved units. The newly-built units mainly include domestic third-generation units represented by CNP 1000 independently researched and developed by CNNC, as well as the third-generation units AP 1000 imported by CNNC from Westinghouse and EPR imported by CGNPC.
In this regard, an expert who did not want to be named told this reporter that on the surface, the proliferation of technical routes will actually bring a lot of impacts to the development of nuclear power in China. "so many routes will first lead to the diversion of nuclear power workers, resulting in scattered professional conversion accuracy of personnel. Once an accident occurs in a power station, other power stations may not be able to provide assistance, and the reliability of the third-generation model has not been tested, so too many routes will increase security risks. "
"At present, the maturity of AP 1000 is still a bit poor, and some testing and verification work has not been completed. We should proceed step by step and act in accordance with the law. The third generation of nuclear power attaches importance to technology mastery, and mastering technology and maintaining safety are the first. " Wen Wen, former deputy chief engineer of the planning department of China National Nuclear Corporation, said that the development progress of nuclear power can be slowed down appropriately, and the scale cannot be pursued excessively.
Qian, former Deputy Director General of the International Atomic Energy Agency, also said in an interview with this reporter that nuclear power should be developed on a large scale under the pressure of energy conservation and emission reduction in China. "But before the domestic nuclear power construction had some fever, major companies were competing for projects, so we should re-examine the safety hazards in project implementation and management. It is a good thing to slow down and review carefully. "