North Korea has resumed work on a light water reactor amidst speculations of a third nuclear test.

The Yongbyon site, a prototype of larger reactors already in the pipeline, is nearing its completion but will take one to two more years before becoming fully operational to provide civilian energy needs.

The site was studied closely through satellite photographs by the institute at the Paul H. Nitze School of Advanced International Studies (SAIS) at Johns Hopkins University. Since 2010 SAIS has been monitoring the construction, which stopped in December to pay respect to North Korean leader Kim Jong-il’s death.

After the completion of the building, heavy components will be installed through the roof. Experts said that light water reactor can be used to produce plutonium and the prototype plant can be easily converted to produce highly enriched uranium for nuclear weapons.