  Type I X-ray bursts are thermonuclear stellar explosions driven by
charged-particle reactions. In the regime for combined H/He-ignition, the main
nuclear flow is dominated by the rp-process (rapid proton-captures and beta+
decays), the 3 alpha-reaction, and the alpha-p-process (a suite of (alpha,p)
and (p,gamma) reactions). The main flow is expected to proceed away from the
valley of stability, eventually reaching the proton drip-line beyond A = 38.
Detailed analysis of the relevant reactions along the main path has only been
scarcely addressed, mainly in the context of parameterized one-zone models. In
this paper, we present a detailed study of the nucleosynthesis and nuclear
processes powering type I X-ray bursts. The reported 11 bursts have been
computed by means of a spherically symmetric (1D), Lagrangian, hydrodynamic
code, linked to a nuclear reaction network that contains 325 isotopes (from 1H
to 107Te), and 1392 nuclear processes. These evolutionary sequences, followed
from the onset of accretion up to the explosion and expansion stages, have been
performed for 2 different metallicities to explore the dependence between the
extension of the main nuclear flow and the initial metal content. We carefully
analyze the dominant reactions and the products of nucleosynthesis, together
with the the physical parameters that determine the light curve (including
recurrence times, ratios between persistent and burst luminosities, or the
extent of the envelope expansion). Results are in qualitative agreement with
the observed properties of some well-studied bursting sources. Leakage from the
predicted SbSnTe-cycle cannot be discarded in some of our models. Production of
12C (and implications for the mechanism that powers superbursts), light
p-nuclei, and the amount of H left over after the bursting episodes will also
be discussed.
