A new search of non-paulian nuclear processes, i.e. processes normally forbidden by the Pauli exclusion principle, was carried out by determining an improved upper limit for the spontaneous emission rate of protons in 2 3 Na and 1 2 7 I. A large set-up of highly radiopure NaI(Tl) crystals was employed; it was placed deeply underground at the Gran Sasso National Laboratory of I.N.F.N. The upper limit on the unit time probability of non-paulian emission of protons with energy E p 10 MeV is λ 4.6 10 - 3 3 s - 1 . The corresponding limit on the relative strength (δ 2 ) for the searched non-paulian transitions has been estimated to be δ 2 1.0 10 - 5 4 .