This is the 14732nd most frequent Turkish word.
reaktörlerin
"Reaktörlerin" means "of the reactors" or "the reactors'".
The word 'reaktörlerin' is in the possessive case indicating ownership or relation, here referring to 'of the reactors'.
Reaktörlerin bakım zamanı geldi.
The time has come for the maintenance of the reactors.
Here, 'reaktörlerin' exhibits the genitive case showing the reactors' involvement or attribute regarding safety.
Reaktörlerin güvenliğe katkısı büyüktür.
The reactors' contribution to safety is substantial.
In this sentence, 'reaktörlerin' refers to the reactors in the sense of needing the cooling action, displaying grammatical use case for indicating the subject of the action.