  The feasibility of a next generation underground water Cherenkov detector is
examined and a conceptual design (UNO) is presented. The design has a linear
detector configuration with a total volume of 650 kton which is 13 times the
total volume of the Super-Kamiokande detector. It corresponds to a 20 times
increase in fiducial volume for physics analyses. The physics goals of UNO are
to increase the sensitivity of the searches for nucleon decays about a factor
of ten and to make precision measurements of the solar and atmospheric neutrino
properties. In addition, the detection sensitivity for Supernova neutrinos will
reach as far as the Andromeda galaxy.
