The International Nuclear Event Scale (INES) is like a scale for measuring the severity of nuclear accidents. It range from 1 to 7. Level 1 is a small event with no safety consequences, while Level 7 is the most serious kind of accident. Level 1 events might include a small leak of radioactive material, while Level 7 events might include something like a very large release of radioactive materials that can spread to many places and cause a lot of health problems.