These scientists brought nuclear and missile knowledge to North Korea.

The North Koreans sent abroad for studies may have acquired knowledge that helped develop their nuclear and missile programs.

A North Korean graduate student at the Harbin Institute of Technology in China. Photo: WSJ.

When North Korea tested a hydrogen bomb last weekend, many questioned why its nuclear program had progressed so rapidly, despite international efforts to prevent it from gaining access to advanced weapons technologies.

According to the WSJ, the answer may lie in North Korean scientists who are sent to study abroad, particularly in China, and then bring back in-depth knowledge of nuclear and missile technology.

When North Korea began pursuing its nuclear weapons program, it relied on technology and experts from the Soviet Union, and later from Iran and Pakistan. Now, it can rely on its own scientists, making Pyongyang's nuclear ambitions even harder to contain.

"We should pay attention to North Korean researchers abroad, especially in China," said Katsuhisa Furukawa, a member of the UN expert panel that monitored sanctions against North Korea from 2011 to 2016.

Following North Korea's second missile test in 2009, the UN imposed a package of sanctions, urging countries to "prevent teaching or training in specialized skills" that could help North Korea develop missiles and nuclear weapons. In 2016, in response to North Korea's fourth nuclear test, the UN banned the teaching of certain subjects, such as materials science, to its citizens.

One of the North Korean scientists who studied in China is Kim Kyong Sol, born in 1975. He continued his studies at China's prestigious Harbin Institute of Technology for more than a year after UN sanctions were imposed. At that time, Kim was a graduate student in mechatronics – a blend of mechanical engineering, electronics, and programming. In March, he published a paper in China, co-authored with a senior engineer in the Chinese military's space program.

After reviewing Kim's essay, Furukawa concluded that it fell into a category prohibited under UN sanctions.

The technological knowledge Kim acquired could be used to stabilize spacecraft and absorb vibrations in rocket launch systems, as well as reduce shaking in cars, buildings, and helicopters.

Kim returned to China in June. The Chinese Foreign Ministry said that Beijing had strictly implemented all UN resolutions on North Korea. They declined to comment on Kim's case.

U.S. officials are concerned that Pyongyang took advantage of the United Nations' lack of strict sanctions on education before 2016 to send scientists abroad for studies and bring back knowledge that could be applied in both civilian and military fields.

Some officials fear that even with strict international sanctions in place, Pyongyang may already possess the expertise to pursue its nuclear goals. The Wall Street Journal reported in August that U.S. intelligence had evidence that North Korea was producing its own rocket engines; however, a research center report stated that the engines originated from Ukraine or Russia.

In a February report, UN experts said they found several North Koreans studying physics in Italy and four studying materials science, engineering, and electronic communications in Romania last year, after the UN ban was imposed.

In 2016, UN experts said that two North Koreans had been trained at an Indian space technology center before being banned. Since 1996, 32 people had been trained there, including one who held a leadership position at Pyongyang's satellite control center. The Indian space technology center said it no longer accepts North Koreans.

China has been a popular destination for many North Korean scientists in recent years. According to the Chinese Ministry of Education, 1,086 North Korean graduate students studied in China in 2015. The ministry did not specify which universities or fields of study they attended.

According to research by South Korean University Hallym, essays written by North Korean graduate students in China between 2011 and 2016 were primarily in physics, engineering, mathematics, metallurgy, and materials science. Following sanctions, North Korean graduate students expanded into civilian fields such as medicine and mining, but also covered some of the banned areas, including metal foams for radiation protection.

Harbin Institute of Technology at a space technology event in April. Photo: Zuma Press.

Sending scientists abroad for training and granting them numerous privileges domestically is central to Kim Jong-un's Byungjin (parallel development) policy, which involves the simultaneous development of nuclear weapons and the economy – a policy he has pursued since coming to power.

North Korean scientist Kim Kyong Sol came to China under a cooperation agreement that several Chinese universities signed with North Korean universities since 2010, including two universities that UN experts say have provided personnel and technology for Pyongyang's nuclear program: Kim Il-sung University and Kim Kaek University of Technology.

Kim and other North Koreans lived quietly while studying at the Harbin Institute of Technology. They stayed in two-bedroom dormitories and rarely interacted with other students. They all received scholarships from the Chinese government, which included free accommodation, tuition, and a monthly stipend of about 3,000 yuan (US$450).

David Albright, a former UN weapons watchdog, says it's common for countries wanting to develop weapons of mass destruction to seek knowledge abroad. They often send scientists to study and attend conferences. Chinese engineering schools and training programs offer "opportunities to interact with people who have sensitive information, such as Chinese people who have been involved in military programs."

The Harbin Institute of Technology (HIT), where Kim studied, is one of China's leading engineering schools. They conducted classified research on defense and space. Chen Zhaobo, Kim's professor at HIT, said that during his time there, Kim did not have access to China's top defense technology, but his research would have applications in both civilian and military fields, including space.

Norman Wereley, a professor of aerospace engineering at the University of Maryland, believes Kim's research is quite fundamental but could help him do more complex work back home. "He might think, 'If I want to control vibrations in a missile system, I already know how to do that,'" Wereley said. "I don't think he went to school for purely academic reasons."

According to VNE