A miniseries about a 1980s nuclear disaster could easily have proved radioactive to viewers. Instead, HBO’s Chernobyl has turned into an unlikely ratings hit. The network says its five-part miniseries, which wrapped Monday night, has to date attracted a cumulative audience of more than 6 million viewers across all HBO platforms. In a sign of strong word-of-mouth, the critically lauded series also saw its linear ratings tick up between each of its broadcasts last month, an exceedingly rare occurrence in the current TV environment. Once final streaming and on-demand numbers get tallied later this month, Chernobylcould even end up reaching roughly as many viewers as last year’s Amy Adams–led Sharp Objects.