As Japan edges closer to the first restart of a nuclear plant under new tighter regulations, experts warned on Monday that it's difficult to predict volcanic hazards and called for more debate on the risks posed by volcanic eruptions.

Last month, the Nuclear Regulation Authority said the risks of volcanic eruptions around the Sendai plant — located in a region of active volcanic sites in Kyushu — are negligible during its life span.

It was a safety nod that hinges on the plant's operator, Kyushu Electric Power Co., continuing to monitor the state of volcanoes and taking appropriate measures if any signs of change are observed.