Signs of nuclear enrichment at Yongbyon

Satellite imagery analysis of the Yongbyon nuclear complex by 38 North in November, which shows signs that the reactor at the facility is in operation again. [YONHAP]

Uranium enrichment at North Korea's Yongbyon nuclear complex appears to be underway once more as satellite images show the melting of snow piled on buildings used for uranium enrichment, according to a former official at the UN's atomic watchdog.

Enriched uranium is used as fissile material in both nuclear weapons and civilian nuclear energy production.

In an interview with Voice of America (VoA) released Monday, Oli Heinonen, who previously served as deputy director of the International Atomic Energy Agency (IAEA) and is currently a fellow with the 38 North program at the Stimson Center, a Washington-based think tank, said satellite images of the Yongbyon nuclear facility taken on Feb. 1 suggested the snow on the uranium enrichment plant (UEP) had melted due to heat emitting from their operation.

“The equipment generates heat, and one can identify sections of a plant operating when snow melts, for example, on roofs after snow storms. Recent imagery from the UEP shows snow melts at various sections of the UEP complex,” Heinonen told the outlet.

“The most important sign are the snow melts in the section, which contains the control room and stations for feeding and withdrawing uranium hexafluoride from the enrichment halls. These sections should only be heated when the facility operates.”

Heinonen, whose work at the IAEA was chiefly concerned with the detection of the misuse of nuclear material or technology, pinpointed other signs on the rooftops of the buildings associated with the enrichment facility that suggest it has started up once more, such as snow melts on support buildings that assemble centrifuges, decontaminate equipment, and distribute electricity.

In August, the IAEA previously reported that the 5-megawatt reactor at the Yongbyon nuclear complex, capable of producing six kilograms of weapons-grade plutonium from spent fuel rods per year, had been restarted.

In that report, IAEA Director General Rafael Mariano Grossi said that a steam plant serving a spent fuel reprocessing plant operated for approximately five months from mid-February to early July, which he called “consistent with the time required to reprocess a complete core of irradiated fuel” from the reactor.

While Heinonen acknowledged that operation of the reactor was more difficult to detect since its change of design, he highlighted release of steam from the turbine hall, discharge of cooling water and the melting of snow over the reactor as the “main indicators” that the reactor is in operation.

Yongbyon began operation in 1986. North Korea agreed to shut down its Yongbyon reactor in 2007 and allow UN nuclear inspectors back into country in exchange for aid amid six-party talks with South Korea, China, Japan, Russia and the United States. It blew up the reactor’s cooling tower in 2008. However, Pyongyang eventually walked away from the negotiating table in 2009.

The IAEA has had no access to North Korea since its inspectors were expelled from the country in 2009. Pyongyang’s sixth and last nuclear test was in September 2017, after which the regime declared a self-imposed moratorium on nuclear and long-range missile testing that the regime threatened to scrap on Jan. 20.

BY MICHAEL LEE [lee.junhyuk@joongang.co.kr]