SEOUL—North Korea is upgrading its nuclear research center at a rapid pace, new satellite imagery analysis suggests, despite Pyongyang’s commitment to denuclearization at a summit with the U.S. this month.
The analysis from 38 North, a North Korea-focused website published by the Stimson Center in Washington, found that Pyongyang, in recent weeks, appears to have modified the cooling system of its plutonium-production reactor and erected a new building near the cooling tower. New Construction could also be observed at the site’s experimental light-water reactor, the report said.
The satellite pictures, captured on June 21, nine days after the Singapore summit meeting between President Donald Trump and North Korean leader Kim Jong Un, showed no immediate effort to begin denuclearization at North Korea’s key nuclear research site.
Shortly after shaking hands with Mr. Kim on June 12, Mr. Trump said the North Korean leader would return home to begin dismantling his country’s nuclear program. “In fact, when he lands—which is going to be shortly—I think that he will start that process right away,” Mr. Trump told reporters.
At a June 21 cabinet meeting, he said the two sides had agreed to “immediately begin total denuclearization of North Korea.”
The statement signed by the two leaders, however, says only that North Korea “commits to work towards complete denuclearization of the Korean Peninsula.”
Mr. Trump said the process could take many years, but, in a tweet posted after his return to the U.S. on June 13, he said: “There is no longer a Nuclear Threat from North Korea.”
The 38 North report, which is based on commercial satellite imagery of North Korea’s Yongbyon nuclear research site captured by Airbus Defence & Space, found that the necessary infrastructure for operations at the experimental light-water reactor “appears externally complete.”
It wasn’t clear whether operations at the reactor had begun, the report said.
Sen. Ed Markey (D., Mass.), the senior Democrat on Senate Foreign Relations East Asia Subcommittee, said the imagery suggests North Korea isn’t adhering to its pledge to denuclearize.
“Despite his claims to the contrary, President Trump got a weaker deal with fewer commitments than any of his predecessors,” Mr. Markey said. “The North Korean nuclear threat continues despite President Trump’s naive assurances.”
Despite concern from some lawmakers, Secretary of State Mike Pompeo didn’t address the matter at a congressional hearing on Wednesday. However, Mr. Pompeo said that he was “optimistic” the U.S. would receive remains of U.S. soldiers killed in the Korean War in 1950-53 from North Korea, a promise by Pyongyang, in the near future and insisted that North Korea understood what steps it needs to take to secure an agreement in which it would give up its nuclear weapons and programs in return for security guarantees and sanctions economic benefits.
“We’ve been pretty unambiguous in our conversations about what we mean when we say complete denuclearization,” he said
North Korea began work in 2010 on experimental light-water reactor, which is several times as large as the plutonium-production reactor at Yongbyon. North Korea has said that it plans to use the new reactor for civilian electricity production. It could also be used to produce fissile material.
Some experts cautioned against relying solely on the satellite pictures as proof of duplicity on the regime’s part.
Andrea Berger, a London-based senior research associate at the Middlebury Institute of International Studies at Monterey, Calif., said that the satellite imagery could only show what is happening on the outside.
“These infrastructure developments provide limited insight into the future direction of North Korea’s nuclear program,” Ms. Berger said.
Even so, she added, the photos “highlight the likelihood that North Korea has not pressed pause on its general nuclear and missile activities while talks are ongoing.”
The 38 North analysts, Frank Pabian, Joseph Bermudez and Jack Liu, said that they expected “business as usual” at the nuclear facility “until specific orders are issued from Pyongyang.”
38 North, in commentary pieces, has generally supported engagement and dialogue with North Korea, though its satellite imagery analyses have captured the regime’s preparations for nuclear and missile tests.
Ahead of the Singapore summit, North Korea invited journalists to watch it blow up its Punggye-ri nuclear test site in its mountainous northeast as a show of its good faith. North Korea didn’t invite any experts, some of whom had said that the site was likely already unusable.
Mr. Kim had said in April that he considered the country’s nuclear program complete, and that no further tests were needed.
At Yongbyon in May 2008, North Korea invited journalists to witness the destruction of a cooling tower as part of a rapprochement with the George W. Bush administration.
But within months, North Korea was threatening to reverse some of its steps toward denuclearization, and less than a year later it conducted its second nuclear test.
This time around, Mr. Pompeo, who met Mr. Kim twice in Pyongyang before a third meeting in Singapore at the summit, has emphasized his belief that Mr. Kim was sincere in his pledges to denuclearize.
“I heard it myself when I visited Pyongyang as Secretary of State, and I heard it again when there was a group together with the president and Chairman Kim,” Mr. Pompeo told CNN this week. “He has been unequivocal in his statement that he’s prepared to do this.”
Mr. Trump told reporters in Singapore that Mr. Kim had told him North Korea was destroying a “major missile-engine testing site,” which he described as another sign of North Korea’s commitment to giving up its nuclear weapons program.
Mr. Trump also pointed to North Korea’s promise to return the remains of U.S. soldiers killed in the Korean War, which was one of the points agreed to by the two sides in the joint statement from the Singapore summit.
Over the weekend, the U.S. began making preparations to receive the remains from North Korea at the inter-Korean border area.
Write to Jonathan Cheng at jonathan.cheng@wsj.com
