Sentence:Thus, during long-term operation of a reactor with a sodium coolant, the [e1]radionuclides[/e1] migrated into [e2]stainless steel[/e2] up to a depth of i00-ii0 ~m.
 e1: radionuclides. 
 e2 : stainless steel.
Answer: Entity-Destination(e1,e2)