A nuclear reactor is a powerful tool to study neutrinos and light dark sector particles. Some reactor experiments have already proven to be extremely useful in these searches. Considering the great interest in the power of the Intensity Frontier to search for new light particles, it would be desirable to explore the possibility of exploiting 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.