North Korea is making progress on building a light-water reactor at its Yongbyon nuclear complex, the Institute for Science and International Security said, citing satellite images taken Feb. 3.

The exterior of the reactor’s turbine building appears complete in the latest photograph, compared with a September image that showed it still under construction, the institute said on its website in a report dated March 5. The dome for the building 60 kilometers north of Pyongyang remains on the ground next to it, according to the report.

The satellite pictures come after North Korea reached an agreement with the U.S. on Feb. 29 to halt uranium enrichment at Yongbyon and permit inspection by international monitors. A light-water reactor uses non-weapons grade uranium to make electricity and is unlikely to be diverted for proliferation use.

The real gauge for the status of North Korea’s nuclear program is at the Yongbyon centrifuge facility, said Stanford University professor Siegfried S. Hecker, who previously visited the plant in November 2010.

"That will tell us a lot about their undisclosed facilities," Hecker said in an e-mailed message.

In November 2010, North Korea showed the Yongbyon plant to visiting U.S. scientists including Hecker, who later said that he saw more than 1,000 centrifuges. While the North claims its nuclear facility is intended to generate electricity, it can be readily converted to produce highly enriched uranium for bombs, Hecker wrote in a report on the university’s website after his trip. (Bloomberg)