When it comes to glass, people often have the impression that it is colorless and transparent. The glass developed by the China Institute of Atomic Energy (CAEA) is unique - it is entirely black and emits a faint blue light when exposed to sunlight. Recently, the Atomic Energy Institute independently developed a two-step 650mm diameter cold crucible glass solidification engineering prototype, which completed a 90 day continuous operation test and harvested about 52 tons of glass solidification bodies. High level radioactive waste (hereinafter referred to as "high-level radioactive waste") can be "sealed" in it. Cold crucible glass solidification technology is currently recognized as the most advanced high-level radioactive waste treatment method in the world Ye Guoan, an academician of the CAS Member and chief scientist of China Nuclear Industry Corporation, told the Science and Technology Daily that "from scratch, the research and development team has struggled for nearly 20 years." The high-level radioactive waste generated after the nuclear energy utilization of the breakthrough high-temperature burning "Guoba" nuclear power plant, with long radiation cycle, high radiation intensity and high biological toxicity, can be called the "best" of nuclear waste. We must firmly confine high-level radioactive waste and nuclear radiation to ensure the safety of the biosphere This is the original intention and obsession of the R&D team. Previous studies have found that glass is an excellent carrier for immobilizing radioactive isotopes and isolating nuclear radiation. To achieve glass solidification of high-level radioactive waste, it is necessary to break through the cold crucible technology. In the 1980s, foreign countries began to develop cold crucible technology. But we can't buy these technologies without them In Ye Guoan's view, in order to master core technologies, one can only rely on self exploration. Cold crucible is a typical "personality" of being cold on the outside and hot on the inside. The crucible wall is surrounded by cooling water pipes, with a temperature below 100 ℃, while the liquid glass inside the crucible has a temperature as high as 1700 ℃. When a cold crucible is in operation, the melted glass touches the crucible wall and forms a cold shell similar to a 'ladle' Ye Guoan said that this cold shell can effectively prevent damage to the crucible material caused by high temperature of liquid glass. But there is a lot of knowledge to burn this layer of "pot cake" well - too thick, low heating efficiency; Too thin to provide effective protection for the crucible body. Accurately controlling the magnetic field distribution of electromagnetic heating is a major challenge that the team must overcome. Long Haoqi, the process leader of the cold crucible team at the Atomic Energy Institute, explained: "Cold crucibles rely on electromagnetic fields to heat glass. The magnetic field cannot directly penetrate the metal crucible wall, but can only pass through narrow crucible wall gaps. If there are too many gaps, the crucible body strength is not enough; if there are too few gaps, the magnetic field strength is not enough." In the scientific research process, various constraints are always interrelated. The diameter of the crucible, the weight of the glass, the number of openings, and the width of the gaps all need to be considered comprehensively. One mistake can result in a complete loss. From 2006 to 2014, the R&D team worked at full capacity and devoted themselves to tackling key issues, learning while doing, and overcoming multiple technical bottlenecks. When the experiment was successful, there was a feeling of 'nine deaths for a lifetime', "Long Haoqi sighed. Nowadays, the cold crucible that has been verified and iteratively improved through hundreds of experiments produces a "pot cake" with moderate thickness and uniform transparency, which can be called perfect. In 2016, a large-scale research prototype of the cold crucible was successfully developed to promote digestion through formula development. Just as everyone was feeling excited, new challenges unexpectedly emerged. The burnup of nuclear fuel in our country is increasing, and the amount of molybdenum, zirconium, lanthanide elements, and precious metals produced by fission is also increasing The person in charge of the cold crucible research and development project at the Atomic Energy Institute, Xianliang, told reporters that these elements are difficult to melt in the glass liquid and will exist in the form of single substances or compounds, causing problems such as crystallization and yellow phase in the glass liquid, thereby blocking the discharge port and causing the operation of the cold crucible to be obstructed or interrupted. The same problem is often encountered by foreign counterparts. Cold crucible must not be picky eaters! But this is not an easy task. Tan Shengheng, the head of the team's formula development, metaphorically said, "The higher the burnup, the more cunning the radioactive nuclides are, and the easier it is for them to 'escape' from the glass solidified body cage." To trap radioactive nuclides much and tightly, the formula of glass is crucial. High level radioactive waste contains more than 30 chemical elements, and the development of glass formulations not only needs to consider the inclusivity of the glass matrix to these elements, but also the interactions between these elements and their impact on the performance of glass waste form products. Taking the abundant presence of molybdenum in high-level radioactive waste as an example, designing a glass formula with stronger ability to contain molybdenum has always been the focus and difficulty of the team's research. The team started researching the inclusion mechanism and melting mechanism of molybdenum in glass, and made every effort to explore the optimal solution for glass formulation. We are like 'old traditional Chinese medicine practitioners' who examine the pulse and repeatedly refine the' prescription 'for resolving the' disease '. "Tan Shengheng used an analogy to say that sometimes the secret to solving problems lies in blindly relying on' medicine introduction '. Research has found that the binding degree and stability of molybdenum element in glass solidified bodies are directly related to the cation field strength and electronegativity in the solidified body network. With this "drug introduction" and relying on the "prescription" database accumulated by the Atomic Energy Institute over the years, the problem of difficult confinement of molybdenum element is easily solved. The new formula not only allows molybdenum to be eaten more and digested better, but also has strong tolerance for other nuclides. After more than two years of hard work, the R&D team has successfully developed a glass formula with high tolerance. With the development of cold crucible glass solidification technology moving from scientific research prototypes to engineering prototypes, engineering challenges have emerged one after another. This prototype, commonly known as the high-level radioactive waste "alchemy furnace", consists of two parts: a rotary calcination furnace and a cold crucible. In actual operation, the former first calcines and transforms high-level radioactive waste, and then the latter melts and solidifies the calcined product with the glass base material. Due to the high level of radioactivity in the working environment, the associated operation between the two needs to be achieved through remote control of a robotic arm. Mechanical arms are far less flexible than human hands, and in order to facilitate their operation, the 'alchemy furnace' needs to be redesigned with modularity In the research stage, the rotary calcination furnace and the cold crucible are two independent entities, each composed of thousands of components. Entering the engineering design phase, it is necessary to break down all of their components and then classify and reassemble them into dozens of different modules. In order to achieve this goal, the team has carried out a large amount of equipment outsourcing work. During the project implementation process, everyone overcame various difficulties and insisted on frequent and long-term business trips for all staff, "Long Haoqi recalled. Some comrades" had elderly parents and young children, "and their children were only over a year old, never taking a day off; Some comrades immediately immerse themselves in the project upon joining, debugging equipment in the field during the day and researching materials in the dormitory at night... studying feed control, rotary calcination, sealed transfer, glass addition, melting and solidification... optimizing each link and module one by one. With the joint efforts of the team and outsourcing units, the "alchemy furnace" has finally been restructured. From the appearance, there doesn't seem to be much change now. In fact, the prototype has undergone a complete transformation internally, "said Xianliang. The results of the 90 day continuous operation test show that the optimized design of the engineering prototype is in good condition, and all performance indicators meet the design requirements. According to the latest data from the China National Nuclear Corporation (CNNC) think tank, as of December 31, 2024, there are 58 nuclear power units in operation in mainland China, with a total installed capacity of 60.88094 million kilowatts; There are a total of 102 nuclear power units in operation, under construction, and approved for construction, with a total installed capacity of 113 million kilowatts, ranking first in the world for two consecutive years. With the breakthrough of safe and efficient treatment technology for high-level radioactive waste, the potential for nuclear energy development in China will be further released. The Third Plenum of the 20th Central Committee of the Communist Party of China proposed to "coordinate and strengthen the tackling of key core technologies" and "promote the integrated development of scientific and technological innovation and industrial innovation". Looking ahead to the future, Ye Guoan is full of confidence: "As long as we have firm confidence in innovation, we will definitely be able to firmly grasp the key core technologies for nuclear energy development in our own hands!" (Xinhua News Agency)