Experimental limits on the proton life-time from the neutrino experiments with heavy water

Experimental data on the number of neutrons born in the heavy water targets of the large neutrino detectors are used to set the limit on the proton life-time independently on decay mode through the reaction d -> n+?. The best up-to-date limit tau_p > 4 10^23 yr with 95% C.L. is derived from the measurements with D_2O target (mass 267 kg) installed near the Bugey reactor. This value can be improved by six orders of magnitude with future data accumulated with the SNO detector containing 1000 t of D_2O.