  Production cross sections and excitation functions of neutron deficient
isotopes of U, Pa and Th have been measured in the reaction of 22Ne + 208Pb.
The comparison of experimental production cross sections of uranium isotopes
with the neutron number 126 <= N <= 134 to the values calculated using
statistical model of nuclear deexcitation has been carried out. There is shown,
that none of the commonly used methods of introduction of shell effect
influence on the production cross sections of evaporations residues allows to
reproduce unambigiously used set of experimental data. Simple semiempirical
method of introduction of shell effect influence in fission channel is proposed
and good agreement with production cross sections of neutron deficient isotopes
in the region from Bi to U is reached.

Nuclear Experiment