The South China Morning Post reported a surprising news that China's top scientists said that nuclear fusion has only 6 years since we generated electricity. According to the scientist, the Chinese government has approved the construction of the world's largest pulse driver and plans to use nuclear fusion energy to connect to the grid to generate electricity in 2028.
Z-FFR fusion power station: a more easy-to-implement nuclear fusion power generation technology
"South China Morning Post" reported that the news was released by Peng Xianjue Academician of of the China Institute of Engineering Physics. He said at an online meeting of Beijing Techxcope (Yuanwang Think Tank) on September 9 that "fusion ignition is a jewel in the crown of science and technology in the world today", but it is too difficult to achieve fusion ignition!
Academician Peng said that there are two types of nuclear fusion ignition. One is laser ignition, which uses high-frequency pulse aurora output to ignite nuclear fusion fuel balls. However, this requires extremely high performance energy storage facilities such as high-performance capacitors and lasers to drive, which is too technically difficult for the moment.
Another type is magnetically constrained plasma nuclear fusion. This uses a magnetic field to constrain extremely high temperature deuterium tritium plasma to make the deuterium and tritium fusion in it. It not only requires continuous heating of the plasma, but also requires long-term constraints. Although a ray of hope has been revealed and breakthroughs have been made in many technologies, it is also very difficult and practical applications are far away.
Academician Peng said that a hybrid reactor containing fusion and fission reactor structure can reduce this difficulty relatively. The central fusion of Z-FFR fusion reactor requires relatively low power and is easy to implement. Use fusion to provide neutron value-added for fission. Fusion only accounts for 5% of the energy of the entire reactor , and fission accounts for 95%. This mixed reactor can use nuclear waste as raw material, and will be the first to realize fusion application! What technology is used for
Z-FFR hybrid heap?
Z-FFR is actually a mixture of two technologies, Z-retraction technology and fission proliferation reactor. There is relatively little information about this on the Internet. The author found a paper in the journal " Chinese Engineering Science ", which can be regarded as clear:
Z-retraction is actually an inertial constraint ending. This is a bit complicated to say. Here we first give a simple concept, which has a constraint with the laser ignition nuclear fusion of the inertial constraint. The inertial constraint is a kind of constraint. Type, but the ignition method is changed to a strong magnetic field generated by pulse current . Its standard definition is as follows:
Tens of MA high current (flowing in the Z direction) through the huge Lorentz force generated by the metal cylindrical thin sleeve (magnetic pressure strength reaches more than one million atmospheric pressure) to push the sleeve plasma to radial inversion (retract) at a high speed, and impact the fusion target pill at a speed of hundreds of kilometers per second, converting kinetic energy into the radiation energy (X-ray) and material internal energy required to achieve fusion. The strong magnetic field generated by the pulse current of
acts on its own current-carrying plasma load, causing it to be imploded to the load axis by being affected by the Lorentz force, and the thermonuclear ignition and combustion are achieved through inertia constraints. Fast Z-pinch technology based on pulse power technology can realize high-efficiency energy conversion from driver electrical energy storage to Z-pinch load kinetic energy or X-ray radiation energy. The Z-pinning Direct Drive laser preheating magnetized sleeve proposed in 2010 combines the advantages of compression heating in inertial constraints and magnetic insulation and alpha heating enhancement in magnetic constraints, which is expected to provide a new way to achieve fusion.
roughly means that it is difficult to break through laser constraints at present, but Z-retraction gives a new direction, making the threshold for fusion lower. The reason is relatively simple. Compared with magnetic constraints , it is as big as several buildings and the fusion cavity is comparable to a small conference room. Z-retraction is obviously much smaller and the energy input is not large. Another key to the
Z-FFR mixer is the subcritical reactor. It uses a low content of uranium-235 as nuclear fuel , mixes a large amount of uranium-238 (this is nuclear waste in ordinary nuclear reactor ), and light water is a subcritical reactor that combines heat transfer, slows down media and combines with pressurized water reactor technology.
Its working process is like this: the energy of high-energy neutrons after deuterium-tritium fusion reaches 14MeV, and they are captured by uranium-235 after deceleration through light water and fission. The 2 to 3 "medium-energy" neutrons generated by their fission are slowed by light water and then captured by uranium-235 and fission again.
Another is that the effect of light water deceleration neutrons is very poor (it is not good). Most of the high-energy neutrons produced by fusion will not be slowed down, but are directly captured by uranium-238. High-energy neutrons can directly fission, and those with slightly lower energy can also make them proliferate into uranium-239. is converted into plutonium-239 after several decays.
plutonium-239 Everyone knows that this is the raw material for making atomic bomb . Of course, this is also a product that can be fissioned. Therefore, the utilization rate of fission in the mixed reactor is unimaginable. For example, the thorium in in the fast neutron proliferation reactor is used to utilize it. These raw materials that can be fissioned or difficult to fission in the original fission reactor can be fissioned, and the utilization rate can reach more than 90%. Currently, the uranium and thorium resources on the earth can provide humans with a thousand years of energy.
Another key is that most of the neutrons in its fission process are provided by Z-pin nuclear fusion. If the Z-FFR hybrid reactor is out of control and the Z-pin nuclear fusion is stopped, then the high-energy neutrons that provide fission will be reduced until they disappear, and the fission reactor will gradually stop, and there is no problem of thermal runaway, which is the safety of the subcritical reactor.
Therefore, the Z-FFR hybrid reactor is quite safe and has a relatively low power requirement for the central fusion reactor. However, its manufacturing cost is still relatively high at present, with the 1 million kilowatt Z-FFR hybrid reactor costing about US$3 billion.
2028 connected to the grid to generate power?
Z-FFR hybrid reactor contains three parts: Z-pin driver, fusion target and explosion chamber, and subcritical energy reactor. The most critical technology of is the Z-pin driver, which requires current in the order of tens of mega-amperes to generate a magnetic pressure of millions of atmospheric pressure, and drives the sleeve plasma to detonate the centrifugal at a high speed of hundreds of kilometers per second to realize target fusion.
Academician Peng believes that the driver currently used for for fusion research that requires at least 60 megaamp current, adopts an LTD topology to reduce the energy and power of the basic discharge unit; increases the front edge time and load radius of the current pulse rise; proposes a new type of magnetic insulated transmission line (MITL) and other technical requirements.
Academician Peng said that the driver with magnetic pressure generated by extremely strong electrical pulses will be built in Chengdu around 2025. The driver will generate 50 million amperes of current, which is about twice the Z-pinning equipment of Sandia National Laboratory in the United States. It is the most critical equipment to complete the Z-FFR hybrid reactor in 2028, which will prepare for the completion of commercial power generation by 2035.
nuclear fusion power generation technology: How many types are there? Why is it so difficult?
If you are not very familiar with the nuclear fusion route, you may be confused about the keywords such as magnetic constraints and inertial constraints mentioned above, but it doesn’t matter. The following will continue to introduce several routes of nuclear fusion and the current general progress.
Types of nuclear fusion and difficulty of realization
Nuclear fission is a process in which heavy nuclei are bombarded by neutrons and fission into two lighter nuclei , and will release 2 to 3 neutrons and a large amount of energy. Nuclear fusion is just the opposite of this process. The process is the process of two light nuclei fusion becoming two heavy nuclei. You read that right. Heavy nuclei fission and light nuclei fusion can release huge energy. The "convergence point" of the two is the iron nucleus. Therefore, once iron is generated in a star, it cannot fusion, and it cannot fission, becoming a "dead ball", which will collapse in the future to form a supernova explosion.
is far from going too far, and then back to nuclear fusion. Although most of the nuclei in front of the iron nucleus can fusion, the implementation is too difficult, so scientists will find the nucleus that is most likely to fusion. This standard is that the binding energy is low. The rough order is that the atom is higher, the higher the binding energy, the lower the binding energy, and the lowest hydrogen (hydrogen has three isotopes, deuterium and tritium, with the highest proportion of deuterium, and deuterium is 0.02%, and the tritium trace amount). However, the two nucleus fusions must first absorb energy, convert one of the protons into neutrons, and then fusion after turning deuterium, which is too high. Only a core like the sun can complete it, and the efficiency is extremely low.
Proton-proton chain reaction of the sun's core
Therefore, scientists directly found deuterium and tritium, which are the fusion materials in hydrogen bomb . Although the conditions of these two fusion materials are relatively low, if there is no particularly high pressure, at least a hundred million degrees of high temperature and maintain this state for a long time, in order to give the deuterium nucleus and tritium a chance to collide and complete fusion. The nuclear fusion route is how to keep these two nuclei at such a high temperature and let them fusion.
The binding energy of the element
As for the current nuclear fusion route, there are two general directions, but multiple branches are divided into these technical routes, but the principles are nothing more than the following two:
- 1, magnetically constrained nuclear fusion ;
- 2, inertially constrained nuclear fusion;
magnetically constrained nuclear fusion is to use a powerful magnetic field to control and compress high-temperature plasma (introduced into the fusion chamber after neutral beam injection heating, wave heating, etc.), so that plasma can undergo as much nuclear fusion reaction as possible in a sufficient density and long enough time.
This is Lawson crITERion (Lawson criterion or Lawson criterion ). It represents the quality factor in nuclear fusion research, and gives the ratio of the minimum required value density of plasma (electronics) products to the "energy limit time", which will lead to the net energy output ratio. Therefore, in a sufficiently mature magnetic constrained nuclear fusion device, increasing the temperature, increasing the magnetic field strength, and extending the constraint time have become the most critical indicators. Therefore, whenever there is a breakthrough, there are basically these three data in the news. How to implement other technologies and what technology is used, and most friends don't understand it.
magnetic constraint: There are many ways to constrain the plasma in the route of ring magnetic field becoming the mainstream
magnetic constraint. The more common ones are magnetic mirror and ring machine. However, magnet mirror technology has long been eliminated. Currently, the tokamak and stellar imitation device are tokarmak and stellar imitation device. Both are ring-shaped, but tokamak is a standard ring, while stellar imitation device is like a ring cut in half and then "crossed" to form a figure 8 shape.
Tokamak and stellar imitator
both belong to the circular magnetic field constraint route. However, supporters of stellar imitator believe that using "distorted" magnetic fields is easier to control when plasma turbulence at high temperatures in the constraint stage. In fact, it seems that it is the same. However, the problems with stellar imitator may be super long and large. It was cancelled in the 1970s, but it was picked up again in the 21st century when Tokamak was in trouble. Currently, stellar imitator is about two generations behind Tokamak.
Tokamak: The origin of ITER
Tokamak is a standard ring magnetic field, and ITER (International Thermonuclear Fusion Experimental Reactor) also belongs to Tokamak. It was first developed by Soviet physicists Igor Tamm and Andrei Sakharov in the 1950s. Because of its natural advantages in stable plasma balance, it was already popular around the world by the 1970s (at that time there were dozens of tokamak devices operating).
But Tokamak encountered a problem, small equipment could not solve it at all, and large Tokamak devices were unable to be built separately, so ITER (International Thermal Fusion Experimental Reactor) came into being, and the participating countries include China, EU , India, Japan, Russia, South Korea and the United States.
experimental reactor was located in France and officially started construction in 2013. The initial budget was 6 billion euros, but the total cost of construction and operation may be as high as 22 billion euros, and the total cost may be between US$45 billion and US$65 billion. Overall, it is expected to be completed and tested before 2025.
Tokamak fatal problem
Tokamak solves the plasma stability problem. Because the plasma is unevenly heated, it will escape in the plasma by the magnetic field, causing energy and fuel loss; in addition, it will also be affected by the vertical displacement event "VDE", causing the plasma to move vertically, touching the upper and lower walls of the vacuum chamber (reaction chamber).
At this time, it will not only cause the plasma constraint state to be destroyed, but also allow plasma of tens of millions or even hundreds of millions of degrees to touch the inner wall of the tokamak, such as Tokamak de built by the French Atomic Energy Commission (CEA) Research Center. Fontenay-aux-Roses (TFR) The plasma in the experimental reactor was out of control and it burned a big hole in the inner wall, almost scrapped!
And the probability of such accidents in the Tokamak experimental reactor is very high, the proportion is about a few percent, which is simply fatal. Fortunately, the current technology can be controlled to avoid damage as much as possible, or reduce the damage to the inner wall during VDE events.
From EAST to CFETR
This is Institute of Plasma Physics, Chinese Academy of Sciences in Hefei, Anhui Province, China The world's first full superconducting magnet tokamak nuclear fusion reaction experimental device built by is an important experimental platform for steady-state magnetic constrained fusion research in the world. Its research results will provide engineering technical support for the future international thermonuclear fusion experimental reactor (ITER):
- On September 28, 2006, EAST completed its first discharge, which is the world's first fully superconducting non-circular cross-section tokamak;
- On December 19, 2008, ITER developed by my country The peak current of the low-temperature power-on experiment of 68kA high-temperature superconducting high-current lead reached 90kA and lasted for 4 minutes, setting the world's highest record for the high-temperature superconducting current lead experiment;
- In 2012, EAST set two world records: high-parameter filter plasma with more than 400 seconds and 20 million degrees; high-constrained (H-mode) plasma discharge with stable repetition of more than 30 seconds;
- On January 28, 2016, EAST successfully achieved ultra-high-temperature long-pulse plasma discharge with electron temperature exceeding 50 million degrees and a duration of 102 seconds, setting a world record for the H-mode running time.
- On November 2, 2016, EAST became the first tokamak to successfully maintain H-mode plasma at about 50 million °C for more than one minute. On December 30, 2021, it achieved a long-pulse high-parameter plasma operation of 1056 seconds, creating a new world record for the operation of the tokamak experimental device
017, China Fusion Engineering Experimental Reactor (CFETR) officially began engineering design, which is my country's next generation superconducting fusion reactor. It seems that China's progress in tokamak technology can reach the level of nuclear fusion reactors, and this progress has been at the leading position in the world.
Another nuclear fusion route is inertial constraint
Inertial constraint technology principle is easier to understand than magnetic constraint. This technology is to make deuterium-tritium fuel into small balls, and then reach an extremely high temperature state under the bombardment of lasers to cause it to fusion. Currently, the more famous one is the NIF (National Ignition Device) in the United States, which was developed by the Rance Livermore National Laboratory.
NIF In the experiment in in July 2013, 192 laser beams were successfully fused into a single pulse, and irradiated on the deuterium-tritium fuel target produced 1.8 megajoules of energy and 500 trillion watts of peak power. The energy emitted by the reaction in this experiment exceeded the energy of the laser, which means that Q is greater than 1, but this is far from enough.
my country also has a divine light series that involves research on the technology of inertial constraint nuclear fusion. my country's solid-state laser technology is more advanced than the United States, but the United States' research investment in inertial constraints is still greater. Compared with magnetic constraints, inertial constraints are equally difficult, such as how to make fuel absorb laser energy at a higher proportion.
However, inertial constraint nuclear fusion has another problem, which is how to extract the energy of fusion, but inertial constraints have a natural advantage that they can be used as nuclear fusion propulsion engines, which is simpler than magnetically constrained nuclear fusion as propulsion engines.
Reference:
https://www.scmp.com/news/china/science/article/3192435/chinas-top-weapons-scientist-says-nuclear-fusion-power-6-years
