Background Events on the Kamiokande Observation of Solar Neutrino Flux

The main background events seem to be caused by the low enegy atmospheric neutrinos. However, the events number can not interpleted by the expected numbers from the relevant cross sections Ve + e--+ Ve + eand Ve + p --+ n +e-. We show the number of background to be consistent with contribution of neutrons generated in nuclear showers initiated by muons underground, following to Ryazhskaya's estimation.