A tantalizing (if that’s the word) excerpt from a 52-minute documentary by David Bickerstaff and Phil Grabsky. “Based on Mario Petrucci’s award-winning book-length poem (split over two books), ‘Heavy Water: a film for Chernobyl’ tells the story of the people who dealt with the disaster at ground-level: the fire-fighters, soldiers, ‘liquidators’, and their families.”