Also we can assume KP aren't that immediately deadly because you can see dozens of crew casually standing around in gasmasks during its boot up sequence in the intro. I don't think they'd do that if it had a result like getting blasted with pure deadly skin-falls-off radiation from being anywhere near it during or after operation.

Kojima particles are fairly vague in description but they firmly seem more dangerous to the environment than having any immediate affect on things around them, and they come off as getting fan-lored into actually melting steel and frying people from indirect exposure.