The HBO series uses just enough of a scientific foundation to ensure its silent moments become all the more impactful.

“300 million billion trillion bullets” is the kind of phrase that, regardless of context, conjures up its own feelings of dread. When placed in the context of a race against time to stop the lethal effects of a power plant on the verge of a meltdown, it’s a collection of words that by themselves are enough to bring about action.

Yet, in “Please Remain Calm,” Episode 2 of the HBO series “Chernobyl,” that’s more the culmination of an understanding of the volatility of nuclear fission rather than an oversimplified substitute. Valery Legasov (Jared Harris) delivers his dire report to a room filled with upper-level Soviet government ministers, but it’s only when he provides an entry-level explanation of what comprises a nuclear reactor that he’s able to drive home the severity of their situation.

“I had to argue with myself all the time,” series writer and creator Craig Mazin explained. “I really tried to create something where you only got as much science as you could take before you then returned to the people and back to emotion. And now their emotions are in context. You understand why it’s bad that these things are happening,” Mazin said.

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That’s the underlying message after Legasov gives Boris Shcherbina (Stellan Skarsgard) a quick Nuclear Reactor Core 101 lesson in midair on their way to the firefighting staging area. It’s helpful to give the audience extra understanding of the mechanics of the efforts to contain the blast, but even the most carefully crafted explanations can’t achieve the desired effect unless the men delivering these details fully absorb it themselves.

“It was important for Jared and Stellan to really understand it. And they do. These are smart guys and they got it. Ultimately it doesn’t matter how convincing I am, if we don’t believe that they understand it, it doesn’t matter,” Mazin said.

In turn, one of the key threads in “Please Remain Calm” is the show beginning to demonstrate how these two men can begin to work in tandem to avert further disaster. “Jared’s character is a scientist, he’s not a motivator of men. And then you have a guy like Stellan’s character who is a Soviet bureaucrat and as a yeller and is obstinate. But once he’s absorbed the truth, he can motivate men because he is those men. And that is fascinating to me. I just think those interesting turns, they make things worth watching,” Mazin said.

Liam Daniel/HBO

In a great example of how “Chernobyl” is able to address a particular issue framed in both directions, the rigorous explanation of the dangers of radiation finds a harrowing complement at episode’s end. The trio of workers charged with wading through infected runoff to help slow the tide of an unfolding crisis also manages to convey the stakes of what happened after the explosion, but this time, without any words. The flashlight fades to black right as the credits do, and that’s pretty much all that the viewer needs to see to understand how dire things are getting.

“How do you create a psychology when you can’t really see anyone’s faces?” series director Johan Renck said, remembering the challenge of depicting those nonverbal moments of fear. “There are no words. There is darkness or whatever it might be to sort of convolute the expression. You don’t even see the eyes of these people — how do you create horror there?”

These twin efforts help to situate everyone in a battle that seems impossible to depict on screen. In the early going of “Chernobyl,” the enemy is an elemental process, unfolding before an endless parade of employees and responders and scientists only in the gradual physical symptoms of exposure. So the mortifying hypotheticals and slowly extinguishing light sources become the dread you can see. In capturing this on screen, Renck drew on a conversation with an actual Chernobyl liquidator.

“He was a nuclear engineer and he was tasked with measuring temperatures within the power plant right after the accident,” Renck said. “And I asked him if he was scared. He said, ‘I was scared. I was scared of the dark. I was walking around and I was terrified of the dark and I was terrified of something falling down onto my head from a collapsing building. The radiation is invisible, I can’t feel it. I can’t see it. It doesn’t affect me directly. So my fears are not activated by that.’ They were activated by much more primitive things.”

That subtle layer of cooperation, even against the backdrop of political bickering, is an early example of how these five installments each have their own distinct atmosphere. If the opening installment is about the horrors of the immediacy of a tragedy, Episode 2 shifts focus and leans into the tension of what’s unfolding when men battle over what to do next.

“It’s probably a wise decision to split it up into five parts so that people can get a little breath in between,” Renck said. “I find it brilliant the way Craig shaped and structured this. The mathematics of it is very interesting, how we start with a story that feels contained over the course of a couple of hours, then as the episodes proceed, the time frame widens out and we become bigger and longer and deeper.”

“It begins with an explosion, but it just spreads and it can only be understood from those multiple perspectives. There’s no way to see it all at once. And inside of those things, there are those interesting stories,” Mazin said. “There is a kind of scientific whodunit that needs its own vibe and there is this tragic, collapsing love story that needs its own space. The only thing that I think ultimately stitches it all together is that there is an undercurrent of loss and despair through all these pieces. The hub is Chernobyl.”

“Chernobyl” airs Monday nights at 9 p.m. on HBO.

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