What are they supposed to be, small thermonuclear warheads? I'm no engineer, but I'd imagine that if they get hit while in their silos, that wouldn't be a good thing.
Even present day nuclear warheads are designed in such a way that a "one-point detonation" is pretty-much impossible (http://en.wikipedia.org/wiki/Swan_(n...One-point_Safe
) (and) by whatever time-period Polaris takes place, there are probably even better safety measures in place). You would possibly destroy the weapon, but you would not get a full-yield from the wepoan's warhead. Getting a full nuclear yield from a warhead requires a precise set of events to occur in a precise sequence. Most likely, you could hit the conventional explosive component of the warhead and cause the nuclear pit to shatter, spreading plutonium (or whatver fissile material they use in the 24th and a half century) all over the place.
Now, you might still have to go out and decon the hull of your starship. but you'd still have a hull to decon.