Okay, so a few logistical nitpicks:
My sister and I saw it from where we lived. The mushroom cloud.
On-site nuclear warhead armed.
Mushroom clouds only occur when a bomb is detonated above ground. The mushroom's 'stalk' is a column of air between the blast area and the ground where the blast is stopped. So if this was an on-site warhead - detonated at ground level - the blast would actually just be a giant half-sphere.
WARNING: Current RAD levels have peaked at 1.2 krads/sec in Keter wing.
Rads are a measurement of dose received, not baseline radioactive activity. Rads are also a US-centric measurement (and an outdated one; the last time they were common was back in the 50s), and the Foundation uses metric; you would use grays or sieverts if you were talking about dose, which are the SI units. However, you're not talking about dose (at least from what I infer) so I recommend using Counts Per Minute; that said, they're also a pretty US-centric and outdated measurement (not to mention useless if you're talking rays and not particles), so if I may recommend changing the sentence to reflect dose measurements:
10:51 a.m. – WARNING: Current radiation levels have peaked in the Keter wing, with personnel dosimeters reading up to 12 sieverts.
(Note: that's a direct conversion from 1.2 kilorads - assuming you're talking about gamma exposure, since it's the reactor doing this - and it's kinda high. Like, unrealistically high. People start worrying at, like, 2 sieverts; 12 is crazy for even brief exposure.)
Anyway, I'm rusty on all this, and given that I never actually pursued health physics as a career like I had been planning to do back in high school, someone with actual nuclear industry experience is welcome to correct me.