We present a complete characterization of a small (9-liter) and mobile 6Li-doped pulse-shape-sensitive plastic scintillator antineutrino detector called SANDD (Segmented AntiNeutrino Directional Detector), constructed for the purpose of near-field reactor monitoring with sensitivity to antineutrino direction. A detailed Monte Carlo simulation code was developed and validated to model the performance of the detector. Analysis cuts were developed to maximize the antineutrino detection efficiency and minimize the background. The antineutrino detection efficiency is estimated to be 18%. An uncertainty of 23 degrees in the direction of the reactor antineutrino flux is predicted from 100 detected antineutrino events. This work was supported by the U.S. Department of Energy National Nuclear Security Administration and Lawrence Livermore National Laboratory [Contract No. DE-AC52-07NA27344, LDRD tracking number 17-ERD-016 and 20-SI-003, release number LLNL-ABS-807668].