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China science

China fires up Hineg generator in Hefei city with goal of making world’s strongest neutron beam using nuclear fusion technology

Research team hopes to hit target within a few years, could be put to civilian use or facilitate downsizing of future nuclear weapons

PUBLISHED : Thursday, 07 January, 2016, 8:01am
UPDATED : Friday, 05 August, 2016, 5:03pm

China has fired up its most powerful neutron generator as it aims to produce the world’s strongest neutron beam using nuclear fusion technology within the next few years.

The technology is expected to have a range of applications from scientific research to the development of military weapons.

The High Intensity D-T fusion Neutron Generator (Hineg) at the Chinese Academy of Sciences’ Institute of Physical Science in Hefei, the capital city of China’s eastern Anhui province, generated more than 1 trillion neutrons per second during its maiden test run on Saturday, according to an announcement on the institute’s website on Wednesday.

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A team of nuclear physicists led by Prof Wu Yican fired deuterium, a heavy and stable isotope of hydrogen, on to a target board made of tritium - another hydrogen isotope that is also highly radioactive.

The two isotopes fused to form helium while releasing a neutron with large amounts of kinetic energy. As the fusion reaction continued, a steady beam of high-energy neutrons was produced.

A neutron generator is a critical component of modern-day nuclear weapons. It creates a fast stream of neutrons to kickstart the chain reaction of fission or fusion materials in a thermal nuclear warhead. An advanced generator can significantly reduce the size and weight of a conventional nuclear weapon.

Moreover, this kind of technology can also be used as a weapon in its own right.

Neutron bombs developed by China and other countries generate powerful neutron beams that can kill all life within a several-kilometre radius while leaving hardware such as buildings and tanks intact. This is because accelerated neutrons can penetrate many inorganic materials. Moreover, they create scant radioactive fallout, which means they don’t poison the environment for a long time afterwards.

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But the powerful neutrons generated at the Hefei facility were mainly intended for civilian use, according to the research team.

Wu’s team said the beam would be used to test the decay of special metals that China developed for future nuclear fusion reactors.

The generator, which harvests neutrons from the fusion of deuterium and tritium particles, can simulate the harsh environment inside a fusion reactor, the team said.

This could make it easier for scientists to find the alloy most capable of withstanding the bombardment of high-energy neutrons that are produced when a fusion reactor works its magic, the research team said.

But the neutron beam generated by Hineg looks weak in comparison to some of its international rivals. Similar facilities in Europe, Russia and Japan have produced beams ten times as strong.

Wu’s team said this was expected because tests are still at an early stage. The next step will be boosting Hineg’s power output 100-fold over the next few years to make it the world’s most powerful fusion neutron source, they added.

However there are still some technical hurdles to surmount.

One of the biggest challenges is how to effectively cool the tritium target board, which is roughly the size of a large coin and can easily overheat.

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When a rapid deuterium stream hits this target, an enormous amount of heat is generated that can melt the board if it is not cooled efficiently.

The research team did not give a precise estimate of when the project would be completed or their targets met.

Dr Li Yuan, an associate professor of physics at Peking University in Beijing who has conducted research with neutron beams but was not involved in this project, said China was still years behind advanced Western nations in terms of neutron generator technology.

“Many experiments requiring a powerful neutron source must be conducted overseas due to the inadequate hardware conditions in China,” he said.

Li said that Hineg’s test run was an important step forward that will help China narrow the gap with other countries such as the Unites States in the coming years.