Measurement of $\sin^2{2\theta_{13}}$ by reactor experiments and its sensitivity

Reactor experiments offer a promising way to determine $\theta_{13}$ and are free from parameter degeneracies in neutrino oscillations. It is described how reactor measurements of $\sin^22\theta_{13}$ can be improved by a near-far detector complex. The experimental lower bound is derived on the sensitivity to $\sin^2{2\theta_{13}}\gtrsim 0.02$ based on the rate analysis, and an idea is given which may enable us to circumvent this bound. It is shown that in the Kashiwazaki-Kariwa plan (KASKA) the sensitivity to $\sin^2{2\theta_{13}}$ is approximately 0.02.