North Korea’s 5-megawatt reactor at Yongbyon is releasing hot water, a sign operations have resumed at the facility capable of producing enough plutonium to make one nuclear bomb a year, according to a U.S. research group.

Satellite imagery taken Sept. 19 shows water being released into the Kuryong River from the reactor facility at North Korea’s main nuclear complex, according to the 38 North website, which is run by the U.S.-Korea Institute at Johns Hopkins University’s School of Advanced International Studies in Washington.

“This release of hot water indicates that the reactor is in operation and the turbine powered electrical generators are producing power,” said Nick Hansen, who wrote the report.

If correct, the reactor will enable North Korea to expand its nuclear weapons capabilities in defiance of world powers and the United Nations. Last month, the International Atomic Energy Agency called on North Korea to halt its nuclear activities, including weapons tests and the restarting of the reactor.

Previously, Hansen had reported that satellite imagery taken Aug. 31 seemed to indicate reactor activity because it showed white steam rising from a building containing turbines and generators powered by the reactor. That was the first sign that a startup process appeared to be under way, since there is no independent confirmation from Kim Jong Un’s regime.

2007 DEAL

North Korea said on April 2 it would restart all facilities at Yongbyon, including the reactor mothballed under a six-nation disarmament deal in 2007, for producing energy and “bolstering up the nuclear armed force both in quality and quantity.”

Signs of activity at the site north of the capital Pyongyang add urgency to efforts to stop North Korea from advancing its nuclear weapons programs. In February, North Korea conducted its third nuclear test, prompting the UN to tighten sanctions against the country.

The U.S. and South Korea agreed on a strategy aimed at thwarting the North’s nuclear threat as the two allies reassess their plan for South Korea to take back wartime command of its forces from the U.S.

“We know that North Korea has increased its threats, clearly, against South Korea, against the United States,” Defense Secretary Chuck Hagel said at a press conference in Seoul yesterday. “It has increased its capabilities, its missile capabilities, its three nuclear tests. So that is constantly forcing a review of our strategies.”

‘TAILORED’ RESPONSE

The U.S. and South Korea have worked up a “tailored” response to the North Korean nuclear threat that has become “real” since the North tested its third device, South Korean Defense Minister Kim Kwan Jin said at the briefing with Hagel after annual security talks.

The U.S. is careful to avoid laying out in advance the circumstances under which nuclear weapons would be used, Ralph Cossa, president of the Hawaii-based Pacific Forum CSIS, said in an e-mail. “It sounds like we are talking about various nuclear scenarios and indicating that various levels of intensity would call for varying levels of response, up to and including, as last resort, a nuclear response,” Cossa said.