Yeah, if it works (which I'm not even sure that it would), it would bear a lot of resemblance to a computer virus and no resemblance at all to a nuclear bomb.
Nuclear does not necessarily mean a bomb
It mean something in the (atomic) nuclei or related to these. Forces, reactions, particles, etc.
Surely chain reaction is a member of this set, but not the only thing. Sure, most nuclear devices we hear about use the chain reaction (power plants, bombs), but an x-rax machine is also somewhat a nuclear device.
Sometimes we even induce neutron capture, which is the opposite of chain reactipn (afaik to create some special isotopes, or to start/sustain a chain reaction).
