Satellite images of North Korea 's Yongbyon nuclear facility have again raised questions about whether the country has restarted its plutonium production reactor -- regarded by western experts as a key component in the development of a nuclear weapon . Researchers point to steam at North Korean facility . They write that it 's a sign that the reactor is near or in operation . Comment: North Korea said in April it would restart nuclear facility in April .
Researchers point to steam at North Korean facility . They write that it 's a sign that the reactor is near or in operation . Comment: North Korea said in April it would restart nuclear facility in April .