It seems like there is some ambiguity around the purpose of the reactor:

"It has the potential to make 25 to 30 megawatts of electricity, enough to power a small town. The plant could also potentially produce about 20 kilograms of weapons-grade plutonium each year"

A bit further down the article says:

"Analysts also found some evidence that could support North Korea’s assertion that the new reactor would be used for power generation. Satellite images appeared to show that power lines and a transmission tower had been erected around the site."

Without weapons inspectors, or some other outside group taking a look, there is no way to know for sure.