It looks as though North Korea has restarted its plutonium reactor at Yongbyon, a move that violates Pyongyang's international pledges and threatens to reinvigorate its nuclear weapons program. It is not clear if the plant is in fact in operation, but it is certain that North Korea will use the possibility of a resumption of activity as a bargaining chip to force its interlocutors in the six-party talks back to the negotiating table. Those talks can only resume when Pyongyang agrees to honor its denuclearization pledge.
While it commenced operations in 1986, the 5 megawatt reactor at the Yongbyon nuclear facility has been in the spotlight for two decades, ever since the North conceded that it was using it to produce plutonium to use for a nuclear weapon. The program was slowed with the announcement of the U.S.-North Korea Agreed Framework in 1994, and was the subject of intense negotiations during the six-party talks. North Korea agreed to close the facility down to demonstrate its commitment to denuclearization: Its cooling tower was blown up in June 2008 as a public statement of its fealty to that goal.
Since then, however, the nuclear talks have gone off the rails. International condemnation of North Korea's missile and nuclear tests allowed Pyongyang to claim that the West, and the United States in particular, had not abandoned its "hostile policy" toward it and used that as an excuse to claim that it would not honor its denuclearization commitment. The six-party talks have remained suspended ever since, with North Korea demanding that it be recognized as a "nuclear weapon state" and the other parties refusing, countering that negotiations cannot resume until Pyongyang acknowledges its pledge to give up its nuclear weapons and related programs.