There aren't separate "reverb" files. The acoustic of the reverberant natural space for wet samples is recorded in the WAV files as an integral element of the pipe samples. The decay portions of the pipe samples are recorded the same way, and you cannot, for example, just lower the volume of everything else from within Hauptwerk.
Maybe I don't understand what you're asking (?). But if you're looking for just "reverb", or a portion of a pipe sample without reverb, to be alterable as a standalone item, you won't find it.
What might be possible is to use just the surround (rear) samples from a surround sample set. But even then, you will see some increase in the fundamental pipe tone — e.g., surround samples aren't just all reverb — they are the sum total of everything heard at the point the microphones were installed in the space when the samples were recorded.