Potassium Iodide
It works by attaching to the iodine receptors in the thyroid. They fill the parking lot so that any radioactive iodine can't park. Good to have a small supply ready to go all the time and not just the fukked up time we live in right meow. You can get it at Amazon or other online retailers
I'm not an expert. But you take it immediately if needed. Or preemptively if you absolutely know you'll need it. I believe you take one pill per day for a couple of weeks. That allows the nastiest radiation enough time to half-life away
Yeah, you are kinda fukked but you still need to shift into survival mode. The KI is just a salt so it probably lasts forever. But it does have a 10 year shelf life
https://en.wikipedia.org/wiki/Potassium_iodide#Nuclear_accidents