Flux is an important source of uncertainties for a reactor neutrino
experiment. It is determined from thermal power measurements, reactor core
simulation, and knowledge of neutrino spectra of fuel isotopes. Past reactor
neutrino experiments have determined the flux to (2-3)% precision. Precision
measurements of mixing angle θ13 by reactor neutrino experiments in
the coming years will use near-far detector configurations. Most uncertainties
from reactor will be canceled out. Understanding of the correlation of
uncertainties is required for θ13 experiments. Precise determination
of reactor neutrino flux will also improve the sensitivity of the
non-proliferation monitoring and future reactor experiments. We will discuss
the flux calculation and recent progresses.Comment: 5 pages. 4 figures. Neutrino 2010 Conference Proceeding. v2:
peer-reviewed versio