Role models are useful! An acquaintance worked as a (somewhat) low-level volunteer at a (somewhat) large sports event. These things are run according to a schedule that is detailed down to the minute, but my acquaintance determined it was unsafe to send the competitors onto the field due to a screw-up by the organisers. (Concurrent event close by occasionally spilled over.)

Despite enormous pressure, he remained firm in advising the competitors to stay inside until the problem was fixed. And they did.

It reminds me that if you're not an ass, and a team player normally, and essential to the operation, you have a surprising amount of leverage even under pressure, and when your formal authority is low. It's okay to politely say "not now" until you're actually ready.

(The difficult bit is, as always, knowing when you're in the wrong!)

Isn't that different? His reason for that was be had info on why the reactor was made that way that was considered a state secret.

As portrayed in the film (and who knows in real life), he only knew there was a flaw in the reactor design; he didn't know – with certainty – that the flaw would lead to an explosion. Under those circumstances, with that kind of uncertainty as well as the classified nature of his knowledge, I consider his answer is even more impressively measured. Anyone savvy about the KGB and the Soviet nuclear power industry would see the red flags go up and drop the line of questioning immediately.