Oh, and by the way, the physics in this episode was stupid even by The Flash's standards. Deuterium isotopes undergoing fission???? No, no, no. Deuterium is an isotope of hydrogen. It's one proton and one neutron. It's used in fusion reactions, the direct opposite of fission. The nuclei of elements lighter than iron release energy when they're fused into heavier nuclei; nuclei heavier than iron release energy when they're split into lighter nuclei. Deuterium is the second-lightest nucleus in existence.
And no, you can't stop a fission reaction by making it fuse. I don't think freezing it would do much good either. The best solution, in theory, would probably be to somehow break up the reaction mass enough to stop the chain reaction. Or put in carbon damping rods like those in a nuclear reactor.
Also, how does sweat drip off of the speedsters' brows when they're in Flashtime? If external time is frozen, they should feel effectively no gravity, because it takes time for gravity to accelerate things downward. Of course, by the same token, they shouldn't be able to stand or run either. Or breathe, though I guess Barry would be accelerating the air molecules he touched. Or hear each other, since it would take a subjective eternity for the sound to pass through the air between them. Have I mentioned how much I hate stories in which characters are sped up in time?
Oh, and breach portals obviously take more than three picoseconds to close. At that speed, they'd blink out between one frame of video and the next. Instead, they collapse slowly enough that we can see it happening.
