  10 MeV proton-irradiation effects on a YBCO-based test structure were
analyzed by measuring its current-voltage (IV) characteristics for different
cumulated fluences. For fluences of up to $\sim$80$\cdot$10$^9$~p/cm$^2$ no
changes in the electrical behavior of the device were observed, while for a
fluence of $\sim$~300$\cdot$10$^9~$ p/cm$^2$ it becomes less conducting. A
detailed analysis of the room temperature IV characteristics based on the
$\gamma$ power exponent parameter [$\gamma=dLn(I)/dLn(V)$] allowed us to reveal
the main conduction mechanisms as well as to establish the equivalent circuit
model of the device. The changes produced in the electrical behavior, in
accordance with Monte Carlo TRIM simulations, suggest that the main effect
induced by protons is the displacement of oxygen atoms within the YBCO lattice,
particularly from oxygen-rich to oxygen-poor areas, where they become trapped.
