The UK's controlled nuclear fusion experiment achieved 59 megajoules in 5 seconds. How far is it from benefiting mankind?

According to news released by some media on February 9, the UK Atomic Energy Research Institute generated 59 megajoules of energy in 5 seconds in a nuclear fusion power generation experiment conducted in December 2021, breaking the previous record of about 22 megajoules of fusion energy set by the device in 1997. This is the latest world energy record to date.

The experiment was conducted in the world's largest nuclear fusion reactor, commonly known as the European Joint Torus, which is a Carmack device, a magnetic confinement device, and its full name is the Joint European Torus (JET). The breakthrough of this experiment shows that the process of promoting nuclear fusion, an almost unlimited and clean energy source, to civilian use has taken a big step forward.

So, will controlled nuclear fusion soon benefit human society?

We can be optimistic and look forward to it, but there is still a long way to go before it can be truly promoted for civilian power generation.

Some reports do not give data that is rigorous and accurate enough, misleading people and leading to blind optimism among the public. For example, a report said: "It is understood that scientists have obtained 11 megawatts of energy in this laboratory, enough to supply 10,000 households."

This is an exaggeration and does not match the news released by the UK Atomic Energy Research Institute on February 9. The official news released by the UK Atomic Energy Research Institute stated that the JET nuclear fusion experiment produced 59 megajoules of sustained energy in 5 seconds. We can understand it as the cumulative energy obtained in 5 seconds, or we can think of it as the maximum energy output in a certain period of time within 5 seconds.

But generally speaking, the energy unit of joule is measured in seconds, so it can be understood that the energy obtained by the JET fusion experiment is 59MJ (megajoule)/s (second), and this energy lasts for 5 seconds. The power generation power is generally measured in kw/h (kilowatt-hour), so 1kw/h is what we usually call 1 kWh. Each kWh is equivalent to 3.6 megajoules of energy, so 59 megajoules is equivalent to about 16.39 kWh.

According to the calculation that 0.2 kWh is needed to boil 1 liter of water, 16.39 kWh can boil about 82 liters of water. If each person drinks 2 liters of water per day, it can supply 164 people with boiled water for one day. Of course, this is only the energy generated per second. If this energy is converted into electricity 100%, it will be 16.39 kWh per second, which can generate about 59,000 kWh of electricity in one hour, and 1.416 million kWh of electricity in 24 hours a day.

For an average household, using air conditioning requires about 20 kWh of electricity. If this is the average electricity consumption per household, 1.416 million kWh of electricity can supply more than 70,000 ordinary households.

It seems that the report that it can supply 10,000 households is still very conservative. But the problem is that this energy must be sustained and can generate electricity continuously before it can be used for civilian purposes. The current experimental process can only last for 5 seconds. Every second, all the energy is converted into energy to obtain 16.39 kWh of electricity. In 5 seconds, only 81.95 kWh of electricity can be obtained, which is only the daily consumption of 4 households.

The results of this experiment are certainly a major breakthrough, but it can only be said that controlled nuclear fusion is advancing little by little like squeezing toothpaste, and it is still a long way from being truly promoted to civilian use.

Several major difficulties in controlled nuclear fusion

Controlled nuclear fusion imitates the nuclear fusion process in the core of the sun, so people call it the "artificial little sun". There is no way to produce the ultra-high pressure of 300 billion atmospheres in the core of the sun on Earth. In order to make up for this deficiency, the temperature must be raised from 15 million degrees Celsius in the core of the sun to more than 100 million degrees Celsius to allow nuclear fusion to proceed autonomously and continuously.

We know that no object on Earth can withstand a temperature of 10,000 degrees, let alone 10,000 10,000 degrees of 100 million degrees. Since there is no container that can hold such high-temperature compounds, scientists can only think of ways from a physical perspective. After years of exploration, three confinement methods have been found, namely: gravity confinement, magnetic confinement, and inertial confinement. Sun nuclear fusion relies on gravity confinement, which cannot be replicated on Earth, so the only way to achieve this is to use the latter two confinement methods.

Today, I will not talk about inertial confinement, but simply talk about magnetic confinement, which is currently the most commonly used in experiments in various countries. Since the atomic nuclei involved in nuclear fusion are positively charged, they will be controlled by the magnetic field. As long as the magnetic field is strong enough, these plasmas will spiral along the direction of the magnetic field lines, just like a trap trapping them inside, so it is also called a magnetic trap, or magnetic confinement.

Magnetic confinement is a physical method that allows this extremely high temperature plasma to be confined in a magnetic trap inside a device without contacting the inner wall of the device or any parts. The most mature magnetic confinement device is the Tokamak device first invented by scientists in the former Soviet Union. Many countries around the world have their own improved Tokamak devices, which have all succeeded in confining plasma, but the confinement time varies.

China is at the forefront of the world in this regard. The Experimental Superconducting Tokamak (EAST), a nuclear fusion device owned by the Chinese Academy of Sciences and located in Hefei, has independent intellectual property rights. In the 2021 test, it set world records of 1,056 seconds of steady-state operation at 70 million degrees Celsius, 101 seconds at 120 million degrees, and 20 seconds at 160 million degrees Celsius.

This world record, the steady-state combustion of nuclear fusion is only measured in seconds, how can it be put into practical use? More importantly, to truly make nuclear fusion energy work, the problem of energy input and output must be solved.

In a tokamak device, creating a magnetic field to confine plasma, heating the nuclear fusion material to 100 million degrees Celsius, and maintaining a steady-state chain reaction requires a large amount of energy input. Therefore, how to make the energy generated by nuclear fusion much higher than the input energy and output the excess energy to convert it into electricity for social benefits is the second and most critical step in solving the confinement problem.

Now the first step is just the beginning, and the second step will be even more arduous.

How long is the road for controlled nuclear fusion to commercial operation?

When nuclear fusion plasma can continuously maintain steady-state chain operation and generate huge energy, a small part of the energy remains in the device to maintain the nuclear fusion chain reaction, and a larger amount of energy needs to be output from the device and converted into electricity. The basic method of converting nuclear fusion thermal energy into electrical energy is to install a heat exchange device at an appropriate distance outside the circular magnetic field, so that the energy in the reaction body is transferred to the heat exchange device in the form of thermal radiation, and then use the now mature method to convert the thermal energy into electrical energy.

This step of experimentation took the scientific community several decades to achieve a balance between input and output (Q value is 0), from negative output to zero output, and then the output power was gradually increased (Q value>0). Now the 59MJ in 5 seconds obtained by the British JET is the highest, but what is the Q value? It has not been disclosed.

There are two types of Q values. One is called QP value, which is the ratio of ignition energy to output energy; the other is QT value, which refers to the ratio of total input energy to output energy. These two Q values ​​are very different. If the overall input energy of the experiment is 400MW, the energy used for ignition is only 50MW, and the output energy is 300MW.

In this way, if the Q value refers to QP, then Q=6, which indicates that the output energy is 6 times the input; if it refers to QT, then Q=0.75, indicating that the output energy is 0.75 times the input energy, which is still a negative output and has no commercial value.

Therefore, the parameters obtained from some experiments, only providing output power, cannot explain the problem. What is the Q value of the British JET experimental data of 59MJ in 5 seconds? The news released did not provide the Q value parameter, so the commercial value cannot be measured. The Q values ​​of China's highest 70 million degrees Celsius for 1056 seconds and 120 million degrees Celsius for 101 seconds were not disclosed.

my country's long-term goal for controlled nuclear fusion is: by 2025, the first phase experiment will achieve 500MW (megawatt) plasma steady-state combustion for 400 seconds, and the second phase experiment will achieve 350MW plasma steady-state long pulse combustion for 3000 seconds; by 2030, the first phase experiment will reach 200MW, 10dpa (the degree of radiation damage will not be explained here), and the second phase experiment will reach 1GW (gigawatt, 1GW=1000MW), 50dpa; the goal for 2050 is to achieve 1GW of power generation connected to the grid.

Among these goals, there is no Q value requirement for the 2025 goal, and the Q value requirement for 2030 is ultimately greater than 10. However, these Q values ​​do not specify whether they are QP or QT, and QP has no commercial value reference, so we understand it as QT value. Even so, if these goals are implemented smoothly, it will take another 30 years for nuclear fusion power generation to be popularized for commercial use.

This is the speed of China. So which is faster, China or foreign countries? We will wait and see. What do you think? Welcome to discuss, thank you for reading.

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