Why its different

Several experts said rating exaggerated. Chernobyl was terrible it blew and they had no containment, said nuclear specialist Murray Jennex,an associate professor at San Diego State University. Their containment has been holding.

The blast at Chernobyl blew roof off a reactor and sent radiation across Europe. Nevertheless,increase in severity level heightens risk of diplomatic tension with Japans neighbours over radioactive fallout.

A level 7 incident means a major release of radiation with a widespread health and environmental impact,while a 5 level is a limited release of radioactive material,with several deaths,according to the International Atomic Energy Agency.