Simplify the following text for a Grade 13 native English-speaking person.
Original: A subsequent appraisal by the International Atomic Energy Agency showed that releases are low and localized from the 16 naval reactors ( reported by the IAEA as having come from seven submarines and the icebreaker `` Lenin '' ) which were dumped at five sites in the Kara Sea .
Simplified: An International Atomic Energy Agency appraisal showed that releases are low and localized .