  We consider electromagnetic corrections to the non-leptonic kaon decay,
$K^+\to\pi^+\pi^0\pi^0$, due to explicit virtual photons only. The decay
amplitude is calculated at one-loop level in the framework of Chiral
Perturbation Theory. The interest in this process is twofold: It is actually
measured by the NA48 collaboration from one side, and, the value of the
amplitude at the $\pi\pi$ threshold gives access to $\pi\pi$ scattering lengths
from the other side. We found that the present correction is about 5 to 6% the
value of the Born amplitude squared. Combined with another piece published
recently, this fixes the size of isospin breaking correction to the amplitude
squared to 7% its one-loop level value in the absence of isospin breaking and
at the center of Dalitz plot.
