The land on the moon can energize the future

The moon once again becomes a popular destination when some countries discuss setting up stations on it. The main reason is the exploitation of fuel supplied to future fusion reactor reactors.

The main fuel source is helium-3 - a light isotope of the helium element used in hot air balloons. In high temperature reactions, helium-3 will mix with other nuclei to release more energy but less waste than the reactions in conventional nuclear reactors.

Gerald Kulcinski, director of the Institute of Fusion Technology at the University of Wisconsin (Madison), said: 'If we can prove that helium-3 burns, this will be a safer and cleaner energy supply than with other nuclear energy sources'.

Only 40 tons of helium-3 has enough energy to meet the entire US electricity demand within a year. However, there is almost no helium-3 on Earth. The closest source to us is the moon.

Some space agencies, especially agencies in China, Russia and India, recently mentioned helium-3 as a reward for their moon projects.

Kulcinski said: 'I don't think the main motivation to return to the moon is helium-3. But in the long run, we will face energy problems. '

Fusion solution

All current nuclear energy is based on nuclear decay, in which a large nucleus (such as uranium) breaks down into many smaller nuclei.

Another reaction is fusion, in which two smaller nuclei combine to form larger nuclei while releasing abundant energy.

The commercial fusion reactor has never been built, but the first pioneering reactor is known as the International Thermonuclear Experimental Reactor (ITER) which has just started at Cadarache, France. It is expected that this reactor will produce the necessary 100 million-degree plasma in 2016, but the power plant that can supply electricity probably won't appear online even if it adds up to 20 years .

The reaction in ITER is the combination of two hydrogen isotopes: deuterium and tritium. It is feared that tritium is radioactive and is a component of nuclear weapons, so be careful when using it.

Another problem is that high mobility multiple neutrons are produced from the deuterium reaction - triti. These neutrons will hit the reactor wall and cause structural damage. According to Kulcinski, it is expected to replace the ITER furnace wall regularly, every 1 to 2 years.

That's why Kulcinski and others support trading in triti with non-radioactive helium-3. "The benefit is that it produces very few neutrons," said Rich Nebel of Emc2 Fusion, based in Santa Fe (NM) . It reduces radioactivity and simplifies technical problems. '

In addition, the products of the helium-3 thermonuclear reactor are electrically charged, so their energy can be directly converted into electricity without going through the process of boiling water to create unnecessary steam.

Helium supply

Despite such attractive benefits, helium-3 is often neglected by fusion researchers because the Earth has very little helium-3. According to Kulcinski, a small amount of helium-3 is collected under unwanted by-products in nuclear weapons sold for about $ 1,000 per gram.

A stable supply of helium-3 may be present in the solar wind, but the earth's magnetic field pushes them away. But this is not the same as the moon. The moon receives about 1 million to 5 million tons of helium-3 from the solar wind during its 4.5 billion year history .

The machine is designed to extract helium-3 from the earth on the moon.The robot will capture sunlight reflected from the light collecting disc and then heat the soil.(Photo: University of Wisconsin)

Evidence was discovered on moon rocks brought back by Apollo and Russian astronauts with a ratio of 10 to 20 parts per billion.

Paul Spudis of the Planet and Moon Research Institute (a research institute funded by NASA) states: 'Heli-3 is present on the moon but at very low density; This means hundreds of millions of tons of rock are needed to get 1 ton of helium-3 '.

According to Spudis, this job requires heating up the moon dust particles to temperatures around 1,300 degrees Fahrenheit (700 degrees Celsius).

Kulcinski and his colleagues have designed a machine that can move on the surface of the moon, take soil on it, and heat it with concentrated sunlight.

This mining machine will produce 300 times more energy than it uses (including the energy that flies to the moon and back), Kulcinski estimates. Meanwhile coal mining brings about 15 to 20 times more energy than input energy. Kulcinski's team estimated that it would cost about $ 800 million to bring each ton of helium-3 back to Earth.

It sounds expensive, but if you can sell fusion energy at the price of gasoline at $ 100 per barrel, the helium-3 will cost $ 10 billion per ton.

Kulcinski said: 'Our real challenge is not getting helium-3, but proving that we can burn it.'

Heli-3 is hard to burn

Burning helium-3 requires more energy than energy to burn hydrogen isotopes. That is why ITER does not consider helium-3 to be a potential energy source at this time.

However, Kulcinski's team is applying a variety of methods, called inertial electrostatic confinement (IEC), to obtain a fusion reaction. Instead of using magnetic fields to keep hot plasma as ITER intends to do, IEC does the work by pushing the hat together again by electric field.

Kulcinski and his colleagues managed to maintain nuclear fusion in the small sample system they created. Emc2 Fusion is also studying similar designs.

However, all studies are about IEC, at least for the moment, requiring a much larger input energy than the energy it produces. Most researchers agree that helium-3 cannot be the first fuel to be used in fusion reactors.

Spudis said: 'We should not say' never ', maybe helium-3 will become an important source of energy in the next century. That time has not yet arrived. I still think it will only be a matter of time. '