  The disappearance of reactor $\bar{\nu}_e$ observed by the Daya Bay
experiment is examined in the framework of a model in which the neutrino is
described by a wave packet with a relative intrinsic momentum dispersion
$\sigma_\text{rel}$. Three pairs of nuclear reactors and eight antineutrino
detectors, each with good energy resolution, distributed among three
experimental halls, supply a high-statistics sample of $\bar{\nu}_e$ acquired
at nine different baselines. This provides a unique platform to test the
effects which arise from the wave packet treatment of neutrino oscillation. The
modified survival probability formula was used to fit Daya Bay data, providing
the first experimental limits: $2.38 \cdot 10^{-17} < \sigma_{\rm rel} < 0.23$.
Treating the dimensions of the reactor cores and detectors as constraints, the
limits are improved: $10^{-14} \lesssim \sigma_{\rm rel} < 0.23$, and an upper
limit of $\sigma_{\rm rel} <0.20$ is obtained. All limits correspond to a 95\%
C.L. Furthermore, the effect due to the wave packet nature of neutrino
oscillation is found to be insignificant for reactor antineutrinos detected by
the Daya Bay experiment thus ensuring an unbiased measurement of the
oscillation parameters $\sin^22\theta_{13}$ and $\Delta m^2_{32}$ within the
plane wave model.
