Plutonium, which is used for nuclear weapons, is believed to be produced at the reactor’s complex.
The United Nations International Atomic Energy Agency (IAEA) was expelled by North Korea in 2009 but still relies on satellite imagery to carry out assessments.
The agency said the reactor has been discharging cooling water since July, a big suggestion that it is operational.
, a nuclear complex with a 5-megawatt reactor, is at the heart of North Korea’s nuclear programme and it has not been operational since December 2018, months after US President Donald Trump met Kim Jong-un in Singapore, according to the IAEA.
The IAEA also discussed a radiochemical laboratory at the same complex, which re-processes spent nuclear fuel.
The latest report said that the laboratory had been operating for five months leading up to July 2021, suggesting that it handled a full batch of spent fuel.
The IAEA said the developments at the reactor and laboratory was “deeply troubling” and a clear violation of UN Security Council resolutions.
The secretive state of North Korea has continued to develop nuclear weapons since IAEA inspectors were expelled, holding its last test in 2017.
Back in January 2021, Kim Jong -un vowed to further develop his nuclear arsenal saying the country will miniaturise warheads and develop tactical weapons and a “super-large hydrogen bomb”.