  We evaluate the sensitivity of large, gadolinium-doped water detectors to
antineutrinos released by nuclear fission explosions, using updated signal and
background models and taking advantage of the capacity for seismic observations
to provide an analysis trigger. Under certain realistic conditions, the
antineutrino signature of a 250-kiloton pure fission explosion could be
identified several hundred kilometers away in a detector about the size of the
largest module currently proposed for a basic physics experiment. In principle,
such an observation could provide rapid confirmation that the seismic signal
coincided with a fission event, possibly useful for international monitoring of
nuclear weapon tests. We discuss the limited potential for seismically cued
antineutrino observations to constrain fission yield, differentiate pure
fission from fusion-enhanced weapon tests, indicate that the seismic evidence
of an explosion had been intentionally masked, or verify the absence of
explosive testing in a targeted area. We conclude that advances in seismic
monitoring and neutrino physics have made the detection of explosion-derived
antineutrinos more conceivable than previously asserted, but the size and cost
of sufficiently sensitive detectors continue to limit applications.
