The bomb casing from a successful nuclear detonation would be entirely atomized and instantly vaporized. The exponential runaway of an atomic chain reaction produces so much radiation (read: light, heat, X-rays, and even gamma rays) in the first nanoseconds that literally every chemical bond is ripped apart, plus so many fast-moving neutrons that many nuclei (even not of the initial fissile material) are either fissioned themselves or altered to radioactive isotopes. Because so much EMR is produced so fast, there literally isn't even time for matter to be physically accelerated away before being absolutely soaked in EM. It's possible that some other matter in the vicinity might be intact and blasted away, but anything within the fireball radius of ~100m is absolute toast.