  A nuclear reactor is a powerful tool to study neutrinos and light dark sector
particles. Some of the reactor experiments have proven to be extremely useful
already. Considering the great interest in the power of intensity frontier to
search for new light particles, it would be desirable to explore more
possibilities to exploit the existing reactor power sources for particle
physics research. We suggest a new reactor experiment searching for the dark
sector. The dark photon can be produced in a reactor core and decay into a
photon and an axion in the presence of the dark axion portal through an
axion-photon-dark photon vertex. We investigate the potential to search for
this new vertex with a monophoton signature and present the expected
sensitivities at some of the existing reactor neutrino experiment detectors.
