  To date, antineutrino experiments built for the purpose of demonstrating a
nonproliferation capability have typically employed organic scintillators, were
situated as close to the core as possible -typically a few meters to tens of
meters distant and have not exceeded a few tons in size. One problem with this
approach is that proximity to the reactor core require accommodation by the
host facility. Water Cherenkov detectors located offsite, at distances of a few
kilometers or greater, may facilitate non-intrusive monitoring and verification
of reactor activities over a large area. As the standoff distance increases,
the detector target mass must scale accordingly. This article quantifies the
degree to which a kiloton-scale gadolinium-doped water-Cherenkov detector can
exclude the existence of undeclared reactors within a specified distance, and
remotely detect the presence of a hidden reactor in the presence of declared
reactors, by verifying the operational power and standoff distance using a
Feldman-Cousins based likelihood analysis. A 1-kton scale (fiducial) water
Cherenkov detector can exclude gigawatt-scale nuclear reactors up to tens of
kilometers within a year. When attempting to identify the specific range and
power of a reactor, the detector energy resolution was not sufficient to
delineate between the two.
