Chernobyl Disaster movie - How will they pull it off?

So not that many people are aware of this but when the Chernobyl Disaster happened, it was almost a LOT worse. If not for 3 power plant-workers who saved the day there was another reactor which was seconds away from exploding (if the gas reached the cooling water or something the whole place would've gone up and supposedly wiped out half of Europe and being uninhabitable for 500,000 years), however these guys managed to dive in the water quick enough and release the valves thus draining the water before the gas reached it.

I don't know if this is 100% accurate as I've not researched it but this is the jist of what happened. Anyway I heard they are making a movie about this, specifically to be adapted from Andrew Leatherbarrow's book '01:23:40', but was wondering what the film will actually be about until that point.

My guess is the actual disaster will take place in the 3rd act and the diving in and saving the day will happen just minutes before the credits role, but what about the first 2 acts? They can't just show the everyday lives of the workers can they? I mean I'd guess we'd spend the first hour getting to know them before their heroic acts but surely there has to be some actual story to it? How do you think they will pull it off? Maybe the narrative won't be like that at all and the entire movie will take place amidst the action (like the recent Dunkirk).

Also if it's set in Chernobyl does that mean it will be a foreign film? Will American actors put on Ukrainian accents but speak in English? How would this work?