Recently nuclear power plant becomes one of the important electric power sources to reduce the greenhouse gasses emission. Nuclear reactor fuel consists of the uranium-235 (235U) enriched uranium and produces the thermal energy via nuclear fission process. Through the reactor operation, uranium-238 (238U) fission also produces the plutonium- 239 (239Pu), which should be strictly under controlled to avoid the diversion to the nuclear weapon for a nonproliferation and safeguard. At this point, monitoring of the nuclear power plant operation and its fuels exchange have important role for the peaceful nuclear energy usage. In this study, we produce the prototype of nuclear reactor monitor based on the plastic scintillator detecting anti-neutrinos, which produced through the several times of beta-decay from the nuclear fission products. In addition, we apply the monitoring performance simulation assuming the 1 ton size detector placed very closely to the reactor core
