  Medium-baseline reactor neutrino oscillation experiments (MBRO) have been
proposed to determine the neutrino mass hierarchy (MH) and to make precise
measurements of the neutrino oscillation parameters. With sufficient
statistics, better than ~3%/\sqrt{E} energy resolution and well understood
energy non-linearity, MH can be determined by analyzing oscillation signals
driven by the atmospheric mass-squared difference in the survival spectrum of
reactor antineutrinos. With such high performance MBRO detectors, oscillation
parameters, such as \sin^22\theta_{12}, \Delta m^2_{21}, and \Delta m^2_{32},
can be measured to sub-percent level, which enables a future test of the PMNS
matrix unitarity to ~1% level and helps the forthcoming neutrinoless double
beta decay experiments to constrain the allowed <m_{\beta \beta}> values.
Combined with results from the next generation long-baseline beam neutrino and
atmospheric neutrino oscillation experiments, the MH determination sensitivity
can reach higher levels. In addition to the neutrino oscillation physics, MBRO
detectors can also be utilized to study geoneutrinos, astrophysical neutrinos
and proton decay. We propose to start a U.S. R&D program to identify, quantify
and fulfill the key challenges essential for the success of MBRO experiments.
