KYIV, Feb 20 - Ukraine's 6 GW Zaporizhia NPP has been running on its only external 750 kV power line for more than a week after a second, backup 330 kV line was damaged, highlighting once again the extremely fragile nuclear safety situation, said International Atomic Energy Agency (IAEA) Director General Rafael Grossi.

"Nuclear power plants (NPPs) need a secure supply of external electricity to cool their reactors and for other essential nuclear safety and security functions. However, this has been a major challenge over the past three years, with Zaporizhia NPP temporarily losing all off-site power eight times," he said.