The Fukushima nuclear power plant uses MOX fuel, and the fuel rod shell is zirconium alloy. Due to the failure of the emergency cooling system caused by the earthquake and tsunami, the cooling water level in the reactor once dropped and the core was exposed. Insufficient cooling makes the temperature of fuel rod shell exceed the limit temperature of zirconium-water reaction, which makes zirconium-water reaction occur and produces a large amount of hydrogen.
The blown roof seen in the news photos is a reactor building, not a containment. Hydrogen produced by zirconium-water reaction in the reactor core is always enclosed in the containment of the factory. At present, it is generally believed that hydrogen leaks into the factory building and is discharged from the gas channel of the pressure relief valve when the pressure in the containment rises. Because the concentration of hydrogen relative to air in the workshop reaches the explosion limit, it will explode after encountering high temperature or even open flame. The power of the explosion tore off the roof of the factory building, leaving only the steel skeleton. At present, there is no conclusive evidence that the explosion caused damage to the containment. Whether the containment is damaged and the cause of the damage need to wait for the final investigation report. The Tragedy of the Nuclear Crisis TEPCO plans to build two more reactors for the first nuclear power plant.
The leakage of radioactive materials and nuclear energy, also known as nuclear meltdown, is a serious sequela of nuclear reactor failure. Although the nuclear radiation released by nuclear leakage is far less than the power and scope of nuclear weapons, it can also cause some biological casualties.
Radioactive material leakage
The Atomic Energy Safety and Security Agency said in a statement that the radiation level in the central control room of the Fukushima Daiichi Nuclear Power Plant 1 Unit of Tokyo Electric Power Company, which was automatically stopped due to the earthquake on June 5438+0 1, has reached 1000 times of the normal value. According to the latest bulletin, the amount of radiation near the gate of this nuclear power plant continues to rise, reaching more than 70 times the normal level at 9: 00 am on 12.
This is the first time that the Japanese authorities have confirmed that radioactive materials from nuclear power plants have leaked to the outside. On the morning of June 12, all residents of Shuangye Town, Oimachi Town and Youkamachi Town around the first and second nuclear power plants affiliated to Tokyo Electric Power Company in Fukushima Prefecture, Japan began to take refuge outside the designated dangerous area, totaling about 20,000 people.
In order to prevent the pressure in the container where the nuclear reactor is placed from rising, resulting in damage to the container, the Atomic Energy Safety and Security Agency has ordered Tokyo Electric Power Company to release the steam in the reactor container of Fukushima Daiichi Nuclear Power Plant 1 and Unit 2 to the outside.
Tokyo Electric Power Company is preparing to release steam from Unit 1, which is the most serious of the three reactors in Fukushima Daiichi Nuclear Power Plant. If the function of cooling the reactor cannot be restored as soon as possible, Units 2 and 3 will take the same measures.
Tokyo Electric Power Company pointed out that the steam in the reactor vessel of Fukushima Daiichi Nuclear Power Plant 1 Unit will pass through a huge pool and then be released from the exhaust pipe. When passing through the water, the radioactive substances will be reduced to a certain extent, and the staff will always observe the quantity of radioactive substances at the outlet of the exhaust pipe. In addition, the Fukushima Daiichi nuclear power plant has lost its cooling function, and the Tokyo Electric Power Company has started to release the steam from the explosion in the reactor vessels of the Fukushima Daiichi nuclear power plant 1 and Unit 2 (photo 15) to reduce the vessel pressure and prevent further damage. The company is also preparing to release steam from two other reactors of the nuclear power plant to the outside.
This is the first time that Japan has taken emergency measures to release steam from nuclear power plants by opening valves. Although this measure may also lead to the leakage of radioactive materials to the external environment, it can avoid the loss of sealing function of nuclear power plants caused by container damage. Banri Kaieda, Japanese Minister of Economy, Trade and Industry, said that according to the prior assessment, even if radioactive substances are released, they will be trace. The security institute pointed out that because the government has decided to expand the refuge area and the wind blows to the sea, it can ensure the safety of residents.
The nuclear leakage continues to deteriorate.
The emergency situation faced by Fukushima 1 nuclear power plant in Japan deteriorated rapidly on June 5. First, the shell of reactor 2 was damaged in the explosion, which led to the continuous outflow of cooling water containing radiation. Then, the originally calm No.4 reactor caught fire and a large amount of radioactive materials leaked. Japanese Prime Minister Naoto Kan immediately issued an order requiring residents within 30 kilometers of the nuclear power plant to stay at home to avoid danger. It is reported that members of the Japanese rescue team have been evacuated from the computer room where the No.2 reactor of Fukushima 1 Nuclear Power Station is located, which indicates that the thick steel shell of the reactor may be "seriously damaged" or even "out of control" due to the explosion in the early morning of 15. The Japanese government issued a warning that the Fukushima 1 nuclear power plant may be leaking more radioactive materials, posing a serious threat to people's health.
A Japanese government spokesman said that although there is no nuclear fuel in use in the No.4 reactor of Fukushima nuclear power plant, a large number of used fuel rods are stored. Therefore, rescuers are trying their best to put out the fire and prevent these "nuclear wastes" that also need to be cooled from continuing to have serious leakage accidents. The latest progress mentioned above shows that the situation of Fukushima 1 nuclear power plant may turn sharply and become out of control.
Once rescuers can't return to Fukushima nuclear power plant soon and continue to "reduce fever" for these four reactors, the fuel in the reactor core will "completely melt" due to excessive temperature. In that case, the hot nuclear fuel like lava will break through the shackles of the reactor fuel tank 15 cm thick steel structure protective body, bringing irreparable nuclear disaster to Japan and neighboring countries.
Previously, due to valve failure, Japanese rescuers could not open the exhaust port of No.2 reactor, resulting in extremely high pressure in the reactor, and at the same time, seawater for cooling the reactor could not be injected into it. This means that the last method used in Japan to cool the reactor failed, so that a large amount of nuclear fuel was exposed to the air for several hours, and there was a great possibility of nuclear leakage.
Although rescuers finally repaired the pressure relief valve, seawater could not completely overflow the hot fuel rods. As a result, the temperature of the No.2 reactor continued to rise until a violent explosion occurred. At present, the Japanese government and the Fukushima nuclear power plant still insist that there will be no serious leakage accident like the Chernobyl nuclear power plant in the former Soviet Union.
At present, Japan can only continue to inject water into four reactors to cool down, and at the same time, it constantly discharges steam with radioactive pollutants. It is hoped that the local area will always maintain a westerly wind and not blow east and south winds, otherwise both Tokyo, the capital of Japan, and the Korean Peninsula will be polluted. At the same time, it is to wait for the reactor to cool naturally to a safe state, and then completely seal it up and abandon the nuclear power plant. Radioactive substances detected around the nuclear power plant in Japan include iodine 13 1 and cesium 137. Among them, iodine 13 1 may cause thyroid diseases once inhaled by human body. The Japanese government has planned to distribute iodine tablets to residents near the nuclear power plant to prevent iodine 13 1 radiation. Relevant data show that cesium 137 will cause damage to human hematopoietic system and nervous system. American analysts pointed out that the current state of Fukushima nuclear power plant in Japan is similar to the nuclear accident at Three Mile Island nuclear power plant in Pennsylvania in 1979. International nuclear accidents are classified into zero to seven levels according to their severity. The three mile island nuclear accident in the United States was rated as level 5. At that time, due to the failure of the refrigeration system, a large number of radioactive materials leaked, and at least 6.5438+0.5 million residents were forced to evacuate.
Zhang Zhe, a reporter from the World Wide Web, reported that on March 15, Yonhap News Agency quoted Japanese media as saying that radioactive materials leaked from the Fukushima nuclear power plant explosion were spreading to all parts of Japan in the north wind. It is reported that kanto region, including Tokyo, has detected more radioactive materials than usual. The radioactive material detected in Ibaraki Prefecture is 100 times higher than usual, and the radioactive material content in Shennai Prefecture is nearly 10 times higher than usual. In addition, high levels of radioactive materials were also detected in Chiba Prefecture and Chaiyuan Prefecture. Japan's Ministry of Education, Culture, Sports, Science and Technology said that although the detected values have little impact on human health, relevant local departments have been asked to increase the frequency of measurement. According to the Japanese news agency * * * on March 15, the measurement results near Unit 3 of Fukushima nuclear power plant show that the nuclear radiation level exceeds the legal standard by 400 times.
According to Reuters, Swedish officials said on June 17 that low-concentration radioactive particles are drifting eastward from the Fukushima nuclear power plant and are expected to reach North America within a few days. According to the report, Lars-Erik Deher, research director of the Swedish National Defense Research Institute, said that this statement is based on a network of data collected by multiple international monitoring stations. De Haier said that this level will not cause harm to the human body, but it is expected that radioactive particles will cross the Atlantic Ocean and eventually reach Europe. "Usually you can't see these particles, so people don't need to worry too much because the radiation level is very low," he said in a telephone interview.
On March 23rd, according to the website of * * * news agency, Tokyo Electric Power Company of Japan announced on March 23rd that neutron radiation was detected 13 times in the plant area after the accident at Fukushima Daiichi nuclear power plant.
The crisis situation is extremely severe.
The crisis situation is extremely severe.
On June 16, Chairman of the National Nuclear Corporation (NRC) Yasko said that the water in the spent fuel rod storage pool of the No.4 reactor of Fukushima Nuclear Power Plant in Japan had dried up, and the disaster situation was more serious than the official statement of Japan. He said that there is no water in the spent fuel rod storage pool of No.4 reactor, and the radiation reading at the site is "very high", which may affect the ability of rescuers to deal with the aftermath, because there will be deadly radiation at the site in a short time. If Yazko's statement is correct, rescuers will not be able to prevent the spent fuel rods from overheating and eventually melting, and the shells of the spent fuel rods will also burn, releasing radioactive materials to a large area. The United States proposed that the evacuation scope of overseas Chinese near the Fukushima nuclear power plant is wider than that announced by Japan, and there is a big gap between the United States and Japan in assessing the disaster situation. Yukiya Amano, Director General of the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, said that he would go to Japan to get first-hand information. Amano believes that the situation at the Fukushima nuclear power plant in Japan is "very serious", but it is not yet time to assert that it is "out of control".
Although the Japanese Defense Ministry said on June 17, two helicopters of the Ground Self-Defense Force have started to inject water into Unit 3 of the Fukushima Daiichi Nuclear Power Plant. According to NHK TV, at about 1 1 local time on June 5438+07, two helicopters of the Self-Defense Force began to inject water into Unit 3 of the First Nuclear Power Plant. This water injection operation is thought to have been carried out at least four times. The picture shows the ground self-defense force helicopter flying to the nuclear power plant. However, according to the Japan News Network, the Tokyo Electric Power Fukushima Office reported that after the Japanese Ground Self-Defense Force released water into the air on the morning of 17, after measurement, the nuclear radiation index of Fukushima nuclear power plant has not changed at this stage.
Things have a long way to go.
Tired Japanese engineers connected cables outside the Fukushima Daiichi nuclear power plant on Saturday in a race against time to avoid a deadly nuclear radiation crisis, Reuters reported. The leakage level of Fukushima nuclear power plant is at least the same as that of Three Mile Island nuclear accident 1979. However, some experts believe that the Fukushima nuclear accident is more serious than the Three Mile Island incident. The Chernobyl nuclear accident was classified as level 7. Japan suffered an unprecedented triple crisis of earthquake, tsunami and nuclear leakage, which triggered the turmoil in the global financial market, prompted the international community to reassess the safety of nuclear power plants, and also brought Japan the most severe test after the end of World War II.
Engineers also need to connect cables to the nuclear power plant to try to restart the cooling water pump to cool the six nuclear reactors at the Fukushima Daiichi nuclear power plant. Fukushima is located about 240 kilometers north of Tokyo. Nearly 300 engineers worked in the evacuation area of Fukushima nuclear power plant with a radius of 20 kilometers, trying to find a solution to restart the cooling water pump to cool four reactor fuel rods. "TEPCO has connected external transmission lines and confirmed that it can supply power," TEPCO said in a statement. At the same time, the fire truck sprayed water on the No.3 reactor all night to cool its fuel rods, because the No.3 reactor used mixed oxide fuel of uranium and polonium, a highly toxic substance.
Tokyo Electric Power officials said that before starting the cooling water pump of No.2 reactor, engineers are laying another 1 .480m cable in the nuclear power plant, and then the cooling water pumps of1,No.3 and No.4 reactors will be started one after another at the weekend. If the cooling water pump can be started, the battle against nuclear radiation will turn around. "If they successfully start the cooling facilities and run them successfully, it will be an important step to ensure the stability of the nuclear power plant," said EricMoore, a nuclear power expert at FocalPoint, an American consulting firm. However, if TEPCO's efforts still fail, it will face the last choice-"sealing the reactor with concrete" to prevent catastrophic nuclear leakage. 1986 the huge leakage accident of Chernobyl nuclear power plant was finally solved through the "sealed" reactor. As of March 28th, according to the detected data, Japan's nuclear leakage has reached the pollution level of Chernobyl nuclear power plant.
According to the news of Japan's Sankei Shimbun on March 25th, Tokyo Electric Power Company announced at a press conference on the morning of 25th that the Fukushima Daiichi nuclear power plant was in a dangerous situation that could not be underestimated due to the severe impact of the earthquake. On 25th, it was detected that the underground water radiation of the nuclear power plant 1 and No.2 reactor was abnormal, which was 10000 times of the normal value, and the emergency repair work was temporarily stopped.
Unpredictable and not optimistic
It is reported that in the hydrogen explosion on March 15, the pressure control room connected with the containment inside the No.2 reactor was damaged, and a large amount of water accumulated in the reactor basement due to water injection cooling work. Following the abnormal water accumulation in the basement of 1 reactor, the radiation amount of underground water accumulation in reactor 2 is 10000 times of the normal state.
In addition, the repair work of No.3 reactor, which was interrupted by black smoke, resumed on the 24th, but three workers were seriously affected by nuclear radiation, and two of them were taken to hospital. The abnormal radioactive amount of groundwater in the No.2 reactor has become a major obstacle to the restoration work. At present, the repair work of 1 and 2 reactors has been forced to be completely interrupted.
Japanese Prime Minister Naoto Kan held a press conference on the 25th. He said that the situation of the Fukushima Daiichi nuclear power plant, which was hit hard by the earthquake in northeastern Japan, is still "very unpredictable" and cannot be optimistic at present. He said that Japan has done its best to tide over the nuclear crisis. Naoto Kan also called on residents in the earthquake and tsunami-stricken areas to regain their courage and continue their lives.
A sharp increase in radioactive materials
The Atomic Energy Safety and Security Agency of Japan's Ministry of Economy, Trade and Industry said on the 30th that the radioactive iodine concentration in the waters near the outlet of the Fukushima Daiichi nuclear power plant has reached 3,355 times the legal limit, which is the highest correlation value detected by Japan so far. According to the introduction of the Atomic Energy Safety and Security Institute, seawater samples were collected 330 meters south of the drain of the Fukushima Daiichi Nuclear Power Plant 1 Unit 4 on the afternoon of the 29th. It was found that the concentration of radioactive iodine-13 1 reached 3355 times of the legal limit. In addition, seawater samples collected 50 meters north of the water outlets of Units 5 and 6 on the same day showed that the concentration of radioactive iodine-13 1 also reached 1262 times of the legal limit.
* * * News Agency quoted Hidehiko Nishiyama, spokesman of the Atomic Energy Safety and Security Agency, as saying that the specific reason for the increase in the concentration of radioactive substances in seawater is not clear, but data collected by Tokyo Electric Power Company show that radioactive substances leaked from nuclear power plants may have entered the sea. Hidehiko Nishiyama also said that the polluted seawater will not affect people's health at this stage. All residents within 20 kilometers around the nuclear power plant have been evacuated, and there are no fishing boats in the waters near the nuclear power plant.
A permanently abandoned reactor
According to the Kyodo News Agency, the chairman of Tokyo Electric Power Company, Katsumoto, held a press conference on the 30th, saying, "Objectively speaking, units 1 4 had to be abandoned."
Yi Sheng also apologized for the accident at the nuclear power plant, saying that "the explosion of the factory building and the leakage of radioactive materials have brought us anxiety, worry and trouble, and we are deeply sorry for this". He also said that TEPCO President Masataka Shimizu, who is in the emergency hospital, "will come back to direct emergency rescue soon". At the same time, he also said that the "sarcophagus" way of closing the reactor with concrete and iron plates like the Chernobyl nuclear power plant is "also a plan".
After the Tokyo Electric Power Company said that units 1 4 of Fukushima Daiichi Nuclear Power Plant would be scrapped, Yukio Edano, Chief Cabinet Secretary of Japan, said on March 30th, 20 1 1 that units 5 and 6 would also be scrapped. At this point, the Fukushima Daiichi nuclear power plant will all be permanently scrapped.
The containment was destroyed.
The Japan Atomic Energy Safety Commission said on the 30th that the reactor pressure vessel and containment of the Fukushima Daiichi Nuclear Power Plant 1 Unit 3 should have been damaged.
The nuclear accident rose to level seven.
Japan Broadcasting Association TV 12 reported that the Atomic Energy Safety and Security Agency of Japan's Ministry of Economy, Trade and Industry decided to upgrade the nuclear accident level of Fukushima Daiichi nuclear power plant to level 7. This makes Japan's nuclear accident level the same as that of the Chernobyl nuclear power plant in the Soviet Union.
According to the report, the Atomic Energy Safety and Security Agency believes that the Fukushima Daiichi nuclear power plant leaked radioactive substances that have an impact on human health and the environment, so it upgraded its nuclear accident level to the most serious level 7. The agency also pointed out that the Fukushima Daiichi nuclear power plant released less radioactive materials than the Chernobyl nuclear power plant.
The Atomic Energy Safety and Security Agency and the Japan Atomic Energy Safety Commission will hold a joint press conference on June 5438+02 to announce the detailed reasons for improving the nuclear accident level of the Fukushima Daiichi nuclear power plant.
On March 12, the Atomic Energy Safety and Security Agency initially assessed the nuclear accident level of Fukushima Daiichi Nuclear Power Plant as Grade 4. Since then, the nuclear power plant has experienced the meltdown of reactor fuel and the leakage of radioactive materials to the outside world, and the Atomic Energy Safety and Security Agency upgraded the accident level to level 5 according to international standards.
1986 The nuclear accident at the Chernobyl nuclear power plant in the Soviet Union was defined as the most serious level 7. On April 26th of that year, the No.4 reactor of Chernobyl nuclear power plant exploded in present Ukraine, killing 30 people on the spot and leaking more than 8 tons of radiation. The nuclear accident directly polluted more than 60 thousand square kilometers of land around the power station, and more than 3.2 million people were injured by nuclear radiation, which caused the biggest disaster in the history of peaceful use of nuclear energy.
Expand the accident evacuation area
[7] Yukio Edano, Chief Cabinet Secretary of Japan, said at the press conference on the morning of April 1 1 that the government planned to change the 20-30 km indoor refuge area originally set in Fiona Fang of the Fukushima Daiichi nuclear power plant into an evacuation area, and the specific work was being coordinated with relevant local governments.
Ye Zhi also said: "The area involved this time will not be determined by radius, but based on soil, topography and climate that may lead to a large amount of radioactive material leakage." The practice of changing the evacuation basis may be due to the detection of a large amount of radioactive materials in the restaurant village 40 kilometers away from the first nuclear power plant.
At present, the 20-kilometer evacuation zone in Fiona Fang may become a warning zone, when the government can take mandatory evacuation measures.
The cooling system will be restored indefinitely.
At the same time, TEPCO originally planned to transfer the high-level radioactive sewage of Unit 2 of Fukushima Daiichi Nuclear Power Plant to other places for storage on April 10, but due to the slow progress of preparation, this work was forced to be postponed for one day.
One month has passed since the Fukushima Daiichi nuclear power plant 1 1 accident, and the recovery of the critical nuclear reactor cooling system is still in the foreseeable future.
Japan first diagnosed a leukemia patient suffering from nuclear radiation.
On 2065438+051October 20th, 10, the Japanese government admitted for the first time that the leukemia of a worker working at the site of the nuclear accident at Fukushima Daiichi Nuclear Power Plant was caused by radiation exposure. To this end, the Japanese Ministry of Health, Labor and Welfare has officially issued a "work injury certificate" to this man.
It is reported that this man is an employee of a cooperative enterprise of Tokyo Electric Power Company. After the nuclear accident, he participated in the rescue operation at the scene and suffered from nuclear radiation.
After the man was diagnosed with leukemia, the Japanese Ministry of Health, Labor and Welfare organized relevant experts to set up an investigation meeting according to his application to investigate the causal relationship between leukemia and nuclear radiation, and finally determined that the man's leukemia was caused by nuclear radiation after his on-site operation at the Fukushima Daiichi nuclear power plant.
It is reported that this is also the first accident-related work-related injury application approved by the Japanese government after the Fukushima Daiichi nuclear power plant was hit by the earthquake, tsunami and nuclear accident.