15/07/2017 8:24 AM AEST | Updated 15/07/2017 8:24 AM AEST

North Korea Could Have More Plutonium Than Previously Thought, Report Finds

Satellite images of North Korean facilities have been analysed.

Handout . / Reuters
A satellite image of the Yongbyon nuclear plant in North Korea by 38 North released this week.

New thermal images of North Korea's main nuclear site suggest the unpredictable Communist regime may have more plutonium that previously thought, a leading US think tank has found.

New research from Washington-based 38 North based its findings on satellite images of the radiochemical laboratory at the Yongbyon nuclear plant from September until the end of June. The analysis comes amid growing global concerns at North Korea's military ambitions.

"The Radiochemical Laboratory operated intermittently and there have apparently been at least two unreported reprocessing campaigns to produce an undetermined amount of plutonium that can further increase North Korea's nuclear weapons stockpile," 38 North said.

"This suggests batch rather than continuous processing of spent fuel rods from the 5 MWe Reactor during the period of analysis."

It said increased thermal activity was noted at the Uranium Enrichment Facility, but it was "unclear if this was the result of centrifuge operations or maintenance operations".

However, the paper also noted that the facility was not producing tritium. This is positive news as tritium "is an essential isotope used in the production of boosted yield nuclear weapons and hydrogen bombs", 38 North said.

North Korea has tested five nuclear bombs which have been manufactured using uranium and plutonium. International efforts have so far been unable to shut down the nation's controversial nuclear program.