From a technical point of view, nuclear waste is mainly categorized into three types: highly radioactive, moderately radioactive and low radioactive. Highly radioactive nuclear waste mainly includes spent fuel and its disposals generated by nuclear fuel after power generation. Medium and low-level radioactive nuclear waste generally includes the contaminated equipment of nuclear power plants, testing equipment, hydration systems during operation, exchange resins, wastewater waste liquids, and gloves and other labor protection products, accounting for 99% of all nuclear waste. Medium and low radioactive nuclear waste is less hazardous; high-level radioactive nuclear waste contains a variety of highly hazardous to the human body of highly radioactive elements, such as only 10 milligrams of plutonium can kill, these highly radioactive elements of the half-life of up to tens of thousands of years to 100,000 years ranging. Therefore, various methods of nuclear waste disposal are different.
The unique nature of nuclear waste makes it very troublesome to dispose of:
①Radioactivity: The radioactivity of nuclear waste can not be eliminated by general physical, chemical and biological methods, and can only be reduced by the decay of radionuclides themselves.
②Ray Hazard: When the rays emitted by nuclear waste pass through the material, ionization and excitation occur, which can cause radiation damage to living organisms.
3 ③ heat release: nuclear waste radionuclides through the decay of energy released, when the radionuclide content is high, the release of heat energy will lead to the temperature of the nuclear waste continues to rise, and even make the solution boils itself, the solid melts itself.
2, the world problem
In the past few decades, how to deal with nuclear waste has been the nuclear industry is faced with an unresolved problem. The United States, for example, has been working on the problem for 20 years and has spent tens of billions of dollars in expenditures. The United States in 1987 for the first time in the Nevada mountain range in the deep address structure in the storage of nuclear waste plans, but to date, the implementation of the plan has not made any progress. For the "perennial evil spirit" known as highly radioactive nuclear waste, academics believe that the most appropriate disposal method is a deep geological burial, but because of its construction requirements of special, complex technology, up to now, there is no international molding of a permanent waste discharge depot.
3. Relevant Cases
United States: On March 22, 2013, at least six underground storage tanks containing nuclear waste leaked at the Hanford Nuclear Exclusion Zone in Washington State, United States. The 177 tanks at the site, containing 200 million liters of high-level radioactive nuclear waste, are more than 20 years old and many of them have previously leaked, with an estimated 3.78 million liters of radioactive liquid leaking***. The U.S. government now needs to spend $2 billion a year to clean up the site, a figure that accounts for one-third of the total nuclear cleanup budget for the U.S. A new nuclear waste treatment plant is expected to cost more than $12.3 billion to build at the site, and won't be operational until at least 2019.
Former Soviet Union: During the Cold War in the last century, the former Soviet Union discharged high-level waste from nuclear weapons plants directly into nearby rivers and lakes for cost and other reasons, causing a serious ecological disaster. Lake Garasu, which used to be a haven for wildlife next to the famous atomic energy city of Chelyabinsk, is now a pool of stagnant water polluted by nuclear waste, and according to Russian environmental experts, the lake's ecology won't be restored for more than 100,000 years to come.
1. Sending it into space If it were to wander through the solar system or fall toward the sun, nuclear waste would have a hard time causing environmental damage on Earth. However, how to send nuclear waste into space is still a challenge. This is because the use of rockets to carry it is sometimes associated with launch failures.
2. Deep drilling Deep drilling involves encasing spent nuclear fuel rods in a sealed steel structure and burying them miles underground. The advantage is that drilling can be done in the immediate vicinity of a nuclear reactor, shortening the distance that high-level nuclear waste has to travel before it can be disposed of.
3. Sub-seabed storage Much of the ocean - the seabed - is made up of heavy clay, which is best suited for absorbing radioactive decay products. However, sub-seabed storage requires underwater drilling, and with the "Gulf of Mexico" oil spill as a precedent, it appears that this solution will have to endure for a long time before it can be put into practice. In addition, disposing of nuclear waste in the ocean would require a revision of international agreements.
4. Burying in the subduction zone Burying nuclear waste in the subduction zone (subduction is the process by which one plate is forced down beneath another) would allow spent nuclear fuel rods to travel along the "conveyor belt" of the Earth's tectonic plates and eventually enter the mantle. However, burial in the subduction zone is also a disposal method that violates a number of international treaties.
5. Freezing Nuclear waste, which is generally very hot, is placed in tungsten spheres on a stable ice sheet, where the spheres move downward as the ice melts around them, and the melting ice above them solidifies again. However, the ice sheet would shift, causing the radioactive material to float through the ocean like an iceberg.
6. Sealed in synthetic rock Burying nuclear waste underground requires consideration of how to prevent the waste from contaminating the surrounding soil and water. Synthetic rocks can absorb specific wastes from Shimizu reactors and plutonium nuclear fission. They are a ceramic product that can seal nuclear waste into a lattice to simulate a more geologically stable ore.
7. Use of hydraulic cages Underground nuclear waste storage facilities become especially dangerous once they seep into the groundwater. If a hydraulic cage similar to a three-dimensional trench is constructed around the nuclear waste, the groundwater will not seep into the radioactive material. Future nuclear waste treatment facilities should be leak-proof, and the hydraulic cages are designed to prevent groundwater contamination from occurring.
Over the past 30 years of operation, China's nuclear industry system has accumulated tens of thousands of cubic meters of medium- and low-level solid waste, as well as currently generating about 150 tons of high-level waste annually. In addition, experts speculate that pressure on China's nuclear waste storage space will emerge around 2030, when highly radioactive nuclear waste from nuclear power plants alone will be as high as 3,200 tons a year.
Currently, China has built two repositories for low- and medium-radiation nuclear waste and is preparing to build two more, but does not yet have a high-radiation repository. Two repositories for low- and medium-radiation nuclear waste have been built, located in Yumen, Gansu province, and Beilong, near Daya Bay, Guangdong province.
Medium and low-level radioactive waste disposal: Beilong disposal site, etc.
The Beilong disposal site covers an area of nearly 21 hectares, with a total designed disposal capacity of 80,000 cubic meters, 5 kilometers away from the Daya Bay nuclear power plant and 4 kilometers away from the Ling'ao nuclear power plant, where medium- and low-level radioactive solid wastes generated by the nuclear power plants in Guangdong and the neighboring areas are sent to be permanently disposed of. Since 1991 exploration and site selection to the first temporary storage of the Daya Bay Nuclear Power Station in November 2001, the waste nuclear guide cylinder, *** took 10 years.
As a simpler civil nuclear disposal facility, the Beilong Disposal Site is designed to dispose of 80,000 cubic meters of low- and medium-discharge waste in 70 disposal units within an area of about 130,000 square meters. Each disposal unit is a 17-meter by 17-meter by 7-meter cubic shielded box made of reinforced concrete. Once a disposal cell is filled with waste packages, the concrete slurry will fill the gaps between the waste packages to hold them in place and also provide enhanced shielding. The disposal unit will then be capped with reinforced concrete. Even in the event of an earthquake, it will be an intact concrete block that won't break easily.
The Northwest Disposal Plant is located below the surface, 10-20 meters above the ground; the North Dragon Disposal Site is built on top of the surface, forming a box-like enclosure. This closure is buried to form a hill, on which vegetation will be planted for greening. These two low and medium discharge disposal site, the vicinity of dozens of square kilometers of security barriers.
A medium-low release disposal site generally requires a 300-500 year period of isolation from the outside world.
High-emission waste disposal: "Beishan No. 1" in the depths of the Gobi wall
Both the Beilong disposal site and the Northwest Disposal Site can only store the "soft waste" generated by the nuclear power plant.
In the first half of 2005, the National Defense Science and Industry Commission (NDSC) held a seminar on the disposal of highly radioactive materials, and began planning for medium- and long-term nuclear waste disposal, which was finalized: China will build a permanent repository for highly radioactive materials, with a design life of 10,000 years, and a capacity that can store all of China's nuclear waste for the next 100-200 years, and then permanently seal it off when it's full. That is to say, at least 100 years later, there will be a second permanent HLM repository on the mainland. According to China's nuclear power development plan, the country will identify a site for a permanent high-level radioactive nuclear waste repository around 2015 to 2020.
To avoid adverse impacts on the environment, highly radioactive nuclear waste must undergo a rigorous treatment process. These nuclear wastes are first made into vitrified solids, then packed into metal canisters that can be shielded from radiation, and finally these metal canisters are placed into the repository, which is located 500-1,000 meters underground. Because the half-life of nuclear waste ranges from tens of thousands of years to 100,000 years, the repository must be chosen to ensure that its geological conditions will keep it safe for at least 100,000 years.
Beishan in Dunhuang, Gansu province, has long been rumored to be the mainland's first underground nuclear waste repository, code-named Beishan I. But its exact name is "Beishan I". But its exact name is "Gansu Beishan Pre-Selection Area for High-Level Waste Geological Disposal Repository". Located about 25 kilometers southeast of the Mogao Grottoes in Dunhuang, it is a Gobi Desert comparable in size to that of Hainan Province, and is very sparsely populated, with a population of less than 12,000 in the entire area, which can be said to be so lonely that it doesn't even have echoes except for the sand and gravel and yellow camel grass. The economic development of Beishan is relatively backward, with little mineral resources around, and the construction of a nuclear waste repository will have less impact on economic development. The climate here is also ideal, with only 70 millimeters of annual rainfall and 3,000 millimeters of evaporation, resulting in a very low water table, which reduces the risk of radioactive elements spreading with the groundwater. Beishan also has convenient transportation conditions, with the depot site only 70 to 80 kilometers from the railroad. In addition, the geological conditions of Beishan are very favorable, as it is located in the stable zone of crustal movement, and the site has a complete granite body, which is the best 'protective clothing' against radiation. Experts from the International Atomic Energy Agency (IAEA) said after a visit to Beishan that it is one of the most ideal sites in the world for nuclear waste storage.
Highly radioactive nuclear waste disposal site is urgent
Because until the repository is built, all highly radioactive nuclear waste can only be stored temporarily in the boron pools of nuclear power plants. If we can't build the repository in time, China's nuclear industry will be faced with a situation where there is no place to store nuclear waste.
In this regard, the United States has had a bitter lesson. The U.S. originally planned to build a high-level radioactive nuclear waste repository in 1998, but due to the high technical difficulty, the U.S. government had to extend the completion time to 2010 despite investing a lot of financial and human resources in research. This result directly led to more than 40 nuclear power plants in the United States to store nuclear waste pools are full, resulting in huge economic losses and make the nuclear power plant owners sued the U.S. Department of Energy.
China's high-level nuclear waste repository is scheduled to be completed in 2030-2040, which is already quite urgent. At the same time, the HLW repository is a costly project, with the U.S., for example, budgeting $96.2 billion for its Yucca Mountain repository. According to the future scale of China's nuclear power, China's HLW repository will cost tens of billions of RMB, and will have enough capacity to hold all the future HLW generated by China's nuclear industry. Our repository will confine nuclear waste deep underground forever.