  This study presents a new concept of segmented antineutrino detector based on
hexagonal plastic scintillator bars for detecting antineutrinos from a nuclear
reactor core. The choice of hexagonal scintillator bars is original and
provides compactness. The proposed detector detects antineutrinos via inverse
beta decay (IBD) with the prompt-delayed double coincidence. Owing to its
segmented structure, the background, which satisfies the delayed coincidence
condition can be eliminated by applying proper event selection cuts. In this
manner, the main focus is to determine proper selection criteria to precisely
tag the true IBD events. Monte-Carlo simulation is carried out to understand
the characteristic of the IBD interaction in the proposed detector by using
Geant4 toolkit. A set of event selection criteria is established based on the
simulated data. It is found that a detection efficiency of 10 % can be achieved
with the selection condition applied. It is also shown that fast neutrons,
which constitute the main background source for above-ground detection, can be
effectively eliminated with these selection criteria. The motivation for this
study is to install this compact detector at a short distance (<100 m) from the
Akkuyu Nuclear Power Plant, which is expected to start operation in 2023.
