China detains US scientist who studied North Korea nuclear tests

subgenus chen Youlin ( correct) specialises in using seismologic information to track nuclear tests

China has detained an American scientist for nearly two years on espionage charges without trial, his family says.

Chen Youlin, 54, was arrested in November 2024 during a personal trip to Beijing to visit family, according to hostage advocacy group Global Reach. He is currently the only US citizen the State Department has designated as "wrongfully detained".

Chen specialises in using seismological data to identify nuclear tests, and has undertaken several projects funded by US authorities.

His wife Rong Yufang, also a seismologist, said the suggestion that Chen was involved in espionage "is both wrong and inconsistent with the public and collaborative nature of the work that he has done".

The family had decided to speak out after they saw no sign of Beijing freeing Chen, Rong said through a statement on Global Reach.

When asked about the case at a daily press briefing on Tuesday, China's foreign ministry said its "judicial authorities handle cases in accordance with the law".

"There is no such thing as so-called wrongful detention," the ministry's spokesman Lin Jian told reporters.

In China, espionage convictions can lead to severe penalties such as life imprisonment or death.

Born in China, Chen became a US citizens in 2011. He lives in Boston, Massachusetts.

He specialises in using seismological data to identify nuclear tests, and has undertaken several projects funded by US authorities.

These include a study in December 2020 that looked at seismic data recorded across Asia, including China, to improve methods for nuclear-test monitoring and yield estimation.

Chen's work involved working closely with Chinese colleagues, and Rong says he has always done so "transparently".

"He is doing precisely the kind of people-to-people engagement that the Chinese government says it wants," she adds.

In an interview with Reuters, Rong also claims Chinese authorities have interrogated her husband more than 100 times on his work and that he wasn't allowed to see a lawyer for first 13 months since his detention.

"I have not been able to speak with my husband for over 600 days and am concerned for his health and well-being," she says in the Global Reach statement.

According to Global Reach, there are "suspicions within the US government that Chen's arrest was spurred by China's conduct of nuclear tests in violation of the Comprehensive Nuclear Test Ban Treaty".

The group says Chen's expertise would give China "an opportunity to learn as much as possible about US seismic detection methodologies so they can establish countermeasures that allow them to circumvent the treaty".

The treaty seeks to ban all nuclear explosion tests on Earth, but it has not formally entered into force because several "nuclear-capable" states have not ratified it. Among them are the US and China, which have both established voluntary moratoriums against explosive nuclear testing.

However US intelligence believe China has been developing a new nuclear arsenal. In June 2020, during Donald Trump's first presidency, his administration accused Beijing of conducting an underground nuclear test at the Lop Nur facility in the country's north-west.

China dismissed the claims as unfounded and politically motivated.

The Foley Foundation, another US-based hostage advocacy group, says Chen's health is a concern, noting that he suffers from diabetes, high blood pressure and high cholesterol.

"He needs reliable access to treatment and care that is not available while he is unjustly incarcerated," the group says.

US Senator Edward Markey, a Massachusetts Democrat, says Beijing's "treatment of Chen has undermined [its] partnership [with the US] and may deter other academics from engaging with their colleagues in China".

"It is my hope that increased attention on his unjust detention will force the Chinese government to do the right thing and release Chen," he writes in a statement published on Tuesday.

Details around Chen's detention come a month after China confirmed its arrest of another US scholar, Min Zin, who is a director at a Myanmar-focused think tank.

Beijing has accused Min Zin of spying and endangering Chinese national security.

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