  Using the idea of the instanton approach to quantum tunneling we try to
obtain a method of calculating spontaneous fission rates for nuclei with the
odd number of neutrons or protons. This problem has its origin in the failure
of the adiabatic cranking approximation which serves as the basis in
calculations of fission probabilities. Selfconsistent instanton equations, with
and without pairing, are reviewed and then simplified to non-selfconsistent
versions with phenomenological single-particle potential and seniority pairing
interaction. Solutions of instanton-like equations without pairing and actions
they produce are studied for the Woods-Saxon potential along realistic fission
trajectories. Actions for unpaired particles are combined with cranking actions
for even-even cores and fission hindrance for odd-A nuclei is studied in such a
hybrid model. With the assumed equal mass parameters for neighbouring odd-A and
even-even nuclei, the model shows that freezing the K {\pi} configuration leads
to a large overestimate of the fission hindrance factors. Actions with
adiabatic configurations mostly show not enough hindrance; instanton-like
actions for blocked nucleons correct this, but not sufficiently.
