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Lead scientist of China’s thorium reactor project died working on the computer
Death of nuclear physicist Xu Hongjie came just weeks before the project he led achieved a breakthrough in fourth-generation nuclear power
Victoria Bela
Published: 8:00pm, 4 Nov 2025Updated: 8:15pm, 4 Nov 2025
Xu Hongjie, a nuclear physicist and pioneer of China’s thorium reactor programme, remained engaged and involved in his field until his death at the age of 70, just weeks before a breakthrough in a project he had led.
The former director of the Shanghai Institute of Applied Physics (SINAP) died in Shanghai on September 14, according to an obituary posted by the institute a day after his death; however, the details of his death were not known until the Science and Technology Daily published a memorial article on Monday.
Xu died after midnight while working from home, according to the official newspaper run by the Ministry of Science and Technology.
“Books were spread open on the desk and the mouse had fallen to the floor. On the computer screen, the lecture slides for ‘Introduction to Nuclear Science and Technology’ remained unfinished,” said the memorial.
The official time of his death was recorded as 8.15am, according to the obituary posted by the institute. It said Xu had died of an illness but no exact cause of death has been made public.
Xu had been set to deliver his first lecture of the new semester to students at ShanghaiTech University the following day.
And his death came just weeks before the project he led achieved a breakthrough in fourth-generation nuclear power. On Saturday, China announced that the thorium molten salt reactor (TMSR) project had achieved the world’s first thorium-to-uranium nuclear fuel conversion in an operational nuclear reactor using molten salt as a coolant.
Xu was the project’s chief scientist at SINAP, which is under the Chinese Academy of Sciences (CAS), and was considered the leading scientist of China’s thorium reactor programme.
“He is the kind of strategic scientist who always focuses on the forefront of world science and technology and the major needs of the country,” said Zhou Chong, director of SINAP’s reactor physics department, as quoted by Science and Technology Daily.
“After he guided us through the past six months, we have a clear understanding of the development path of the field of molten salt fluid mechanics in the next 10 to 15 years,” Zhou said.
The experimental TMSR reactor in China’s Gobi Desert in the northwestern province of Gansu is the world’s only operational molten salt reactor loaded with thorium fuel.
Molten salt reactors are fourth-generation advanced nuclear energy systems designed to achieve more sustainable and efficient nuclear power with closed fuel cycles.
They use high-temperature molten salt as a coolant instead of water, which can allow them to operate at higher temperatures and lower pressures, making them more efficient in electricity generation while eliminating the risk of high-pressure accidents.
Thorium – a radioactive element that is abundant in the Earth’s crust – is one of the potential fuel sources for these reactors. Thorium is more abundant than uranium, produces less long-lived nuclear waste and is less easily used to make nuclear weapons.
Some experts say that just one thorium-rich mine in Inner Mongolia could theoretically meet China’s energy needs for tens of thousands of years.
At a closed-door meeting at CAS on April 8, Xu said China “now leads the global frontier” in this field, according to an article in the Guangming Daily.
The US pioneered molten salt reactor technology, building a small test reactor in the 1960s. However, after initial experiments, it abandoned its research in the 1970s in favour of uranium-based systems. It left the research publicly available.
In the meetings, Xu compared the race between the US and China to develop this technology to Aesop’s fable, The Tortoise and the Hare.
“Rabbits sometimes make mistakes or grow lazy. That’s when the tortoise seizes its chance,” Xu said, stating that China had become the “successor” to this technology.
While China has taken the lead in the development of thorium molten salt reactors – one of six designs included within fourth-generation nuclear systems – the US has struggled to revive its development.
Xu, who was born in 1955, graduated from Fudan University with a doctoral degree in nuclear physics and nuclear technology in 1989.
That same year, he joined SINAP as a postdoctoral fellow and was promoted to associate researcher in 1991 and deputy director in 1995. From 2001 to 2009, he served as the institute’s director.
Between 1991 and 1992, Xu spent some time conducting collaborative research at the University of Tokyo’s Institute of Nuclear Physics.
Xu also served as the chairman and general manager of Shanghai Lianhe Rihuan Energy Technology and chairman of the Shanghai Nuclear Society.
In 1995, CAS and the Shanghai municipal government decided to construct the Shanghai Synchrotron Radiation Facility. Xu took responsibility for the project, according to the Science and Technology Daily on Monday.
Under Xu’s leadership, they reportedly built a world-leading third-generation synchrotron radiation light source, which is an advanced facility designed to produce high-brightness light beams.
In 2009, following the completion of the facility, Xu was tasked with leading a thorium reactor project to make the technology a reality, leading to the launch of the TMSR programme in 2011.
In October 2023, the experimental 2-megawatt thorium thermal reactor in the Gobi Desert achieved criticality, or a sustained nuclear chain reaction, and in June 2024, it reached full power operation.
China is constructing a larger thorium molten salt reactor, a 10-megawatt reactor expected to achieve criticality in 2030. The country has also unveiled a design for thorium-powered container ships.
According to state media, the ultimate goal of the TMSR programme is to build a 100-megawatt demonstration project and show its applicability by 2035.
Lead scientist of China’s thorium reactor project died working on the computer
Death of nuclear physicist Xu Hongjie came just weeks before the project he led achieved a breakthrough in fourth-generation nuclear power.
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