Advanced Nuclear Energy Technologies: Towards greater safety and reliability



Nuclear fission energy technology: squeeze nuclear waste, enrich nuclear fuel

In 2016, Zhan Wenlong, an academician of the Chinese Academy of Sciences, visited Hanford, a town on the Columbia River in Washington State. It's the largest radioactive waste disposal site since the United States developed nuclear weapons. There are large, rusted tanks containing enhanced chemical corrosion, highly radioactive nuclear waste.

Zhan remembers the shock: "The United States now spends $2 billion a year to maintain security there." That made him more determined to develop a technology in our country that could dispose of nuclear waste more safely and economically.

In the eyes of scientists, nuclear waste is not "waste", but "spent fuel" that can continue to be used. As early as 2011, the Chinese Academy of Sciences launched the "Future Advanced Nuclear fission energy - ADS Transmutation system" strategic pilot science and technology project (referred to as ADS pilot project), the goal is to use the accelerator to produce high-energy protons, drive spent fuel to continue to "burn". Because the fuel stops "burning" when the accelerator stops running, this technology is internationally recognized as the most promising way to safely dispose of long-lived nuclear waste using transmutation.

By the time Zhan Wenlong visited the United States in 2016, scientists had broken through some of the key core technologies of ADS and completed the design of a new program, a more cost-effective "accelerator Driven Advanced Nuclear Energy System" (ADANES) that can "eat and squeeze" spent fuel.

The new program consists of two parts, one is to industrialize the existing ADS technology, and the other is to develop the spent fuel recycling system (ADRUF). The former is equivalent to "making a furnace", the latter is equivalent to "making fuel".

Zhan Wenlong introduced that according to this program, the utilization rate of uranium resources will be increased from the current less than 1% to more than 95%, and ultimately only need to dispose of less than 5% of nuclear waste, its radioactive life will be shortened from hundreds of thousands of years to 500 years, and 30% of thorium resources can be burned, which will support the development of nuclear power for thousands of years. While achieving the goal of carbon neutrality, it also generates valuable isotopes that can be used for precision targeted radiotherapy and nuclear mobile power.

When the ADANES program is in full swing, the pilot project of "Future Advanced Nuclear fission energy - Thorium-based molten salt Reactor Nuclear Energy System" (TMSR) launched at the same time as the ADS pilot project has also achieved initial results.

"Before the launch of the 'future advanced nuclear fission energy' pilot project in 2011, it has been clear that the Chinese Academy of Sciences will do scientific and technological innovation in the field of nuclear energy." After analyzing the situation, we believe that there are two starting points. One is to develop nuclear waste safe treatment and disposal technology to minimize the nuclear waste that needs geological disposal, aiming at the problems of nuclear waste safety and environmental impact. In response to the shortage of uranium-235 nuclear fuel, we will develop technology to use thorium-232 as nuclear fuel to diversify nuclear fuel sources." Peng Zilong, then director of the Material and Energy Department of the Major Task Bureau of the Chinese Academy of Sciences and secretary of the Discipline Inspection committee of the Ganjiang Innovation Research Institute of the Chinese Academy of Sciences, told the Chinese Science Journal when recalling the pilot project.

TMSR pilot special plan with about 20 years, the first in the world to achieve the application of thorium-based molten salt reactor, while the establishment of thorium-based molten salt reactor industry chain and the corresponding scientific and technological team. In November 2017, the Chinese Academy of Sciences and Gansu Province signed a strategic cooperation framework agreement for fourth-generation advanced nuclear thorium-based molten salt reactors. By May 2021, the main project of TMSR has been basically completed.

Nuclear fusion energy technology: Eastern Hyperring and Divine Light

In the development of nuclear fission energy at the same time, the Chinese Academy of Sciences has a group of researchers to explore another type of future advanced nuclear energy technology - controlled nuclear fusion energy technology.

"Fusion energy is the ultimate goal of nuclear energy development, and fusion energy can make a significant contribution to achieving carbon neutrality." Said Song Yuntao, vice president of the Hefei Institute of Material Sciences and director of the Institute of Plasma Physics.

Nuclear fusion is the equivalent of squeezing a bunch of atoms together and releasing energy. Nuclear fusion reaction conditions are harsh, not only need to reach tens of millions or even hundreds of millions of degrees Celsius of high temperature, but also need enormous pressure. Therefore, how to trigger the reaction is a major difficulty in nuclear fusion energy technology.

Peng Zilong told the "Chinese Science Journal" that researchers at the Chinese Academy of Sciences have two efforts in fusion energy technology, one is magnetic confinement of nuclear fusion, and the other is inertial confinement of nuclear fusion.

Magnetic confinement nuclear fusion, through the Tokamak device to generate a strong magnetic field, the plasma is confined in the smallest possible range and it is continuously heated and maintained at tens of millions or even hundreds of millions of degrees to meet the temperature requirements of nuclear fusion.

As early as the 1970s, the Institute of Plasma Physics at the Hefei Institute of Physical Sciences of the Chinese Academy of Sciences in Hefei began research related to nuclear fusion, and in the 1990s, it started the research of magnetic confinement nuclear fusion energy technology - superconducting tokamak.

In 2006, the Eastern hyperloop, known as the "artificial sun", was officially completed, becoming the world's first fully superconducting tokamak device designed and developed by China. In the same year, the Chinese team led by the Chinese Academy of Sciences joined the International Thermonuclear Experimental Reactor project, becoming an important member of the global exploration of "artificial sun" new energy team.

On December 30, 2021, the Eastern Hyperloop achieved a long pulse of high-parameter plasma at 70 million degrees Celsius for 1056 seconds, which is the first time that humans have achieved artificial solar sustained pulses over 1,000 seconds.

In inertial confinement fusion, the fusion material is made into a target pellet of only about one or two millimeters, and then uniformly fired from all sides into a high-energy laser beam to continuously compress and eventually detonate the pellet, forming a miniature "hydrogen bomb" explosion, generating heat energy. To test this principle, the United States completed the National Ignition Facility (NIF) in 2009.

In China, in the 1960s, the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences started the research process of laser inertial confinement nuclear fusion energy in China. In the 1980s, in order to catch up with the pace of international research, Shanghai Institute of Optical Machinery began a large-scale comprehensive laser device - "divine light" pre-research work, and was completed in 1986, and was called "Divine light - I" after the device was retired in 1994. In 2000 and 2015, China has built Shenguang - II laser device and Shenguang - III host laser device and put into use.

Toward 2060: Scientists' Dreams

For more than 10 years from 2011 to now, the development history and current situation of the "Future advanced nuclear fission energy" pilot project have made Peng Zilong see the advantages of the Chinese Academy of Sciences in developing advanced nuclear energy technology.

"At the beginning, when we were planning the research pilot project, our heart was aiming at things 30 years from now." Peng Zilong said that as a national research institution, the Chinese Academy of Sciences must be more forward-looking in analyzing needs and challenges, and thinking about solutions based on scientific origins and laws.

After the clear goal, the Chinese Academy of Sciences mobilized a large scale, comprehensive innovation force. "Each pilot project involves the participation of more than a dozen research institutes." Peng Zilong memories.

He lamented that as a national strategic scientific and technological force, the mission positioning of the Chinese Academy of Sciences determines its stronger innovation ability and desire. "If the country wants to innovate, the Chinese Academy of Sciences can innovate." Peng Zilong said.

Once again, researchers are ramping up their efforts to achieve carbon neutrality.

As a researcher of advanced nuclear fission energy, Zhan Wenlong has a dream: to build a clean energy oasis on the vast desert Gobi, integrating solar energy, wind energy and safer and more reliable nuclear energy technology, and continuously exporting clean and pollution-free power energy to thousands of households.

Zhan Wenlong introduced that they have broken through the key core technology of ADS, and will build the national major science and technology infrastructure "Accelerator Driven Transmutation Research Device" (CiADS) with high standards and high quality from 2020 to 2027 as planned; For ADRUF, a spent fuel dry processing line for simulated fuel demonstration was built at the same time. At the same time, the overall program of ADANES was optimized. Breakthrough in the key technology and process of mass production of rare isotopes under intense irradiation, and carry out the mass production of precision radiotherapy isotopes.

According to the technological progress, by 2032, they will break through the key core technology of ADRUF, complete the construction of the hot chamber system and carry out the research and development of recycled nuclear fuel, and complete the combustion demonstration based on CiADS; Strive to complete the project of "high-density energy fuel research equipment", a major national science and technology infrastructure, and build super-strong broad-spectrum irradiation facilities and related nuclear materials research and development platforms.

After 2035, they will complete ADANES integrated optimization and industrial application demonstration, provide hard scientific and technological support for carbon neutrality, and achieve industrialization.

As a researcher of advanced nuclear fusion energy, Song Yuntao also has a dream: to build a demonstration project of future nuclear fusion power station within 10 years, and truly realize fusion reactor power generation.

"Time is tight, and China has its own 'time road map.' According to the current technology, it is completely possible to complete the demonstration project of nuclear fusion power generation within 10 years, and it will not be long before mankind can ignite the 'big coal ball' of nuclear fusion." Song Yuntao said.

Whether in the past, present or future, researchers at the Chinese Academy of Sciences have been working towards safer, more reliable and more economical nuclear energy technology. It is these persistence that has lasted for 10 years, 20 years, and more than half a century that has made the development prospect of China's advanced nuclear energy technology promising and the realization of China's carbon neutrality goal in the future.