  Type I X-ray bursts are violent stellar events that take place on the
H/He-rich envelopes of accreting neutron stars. We have investigated the role
played by uncertainties in nuclear processes on the nucleosynthesis
accompanying these explosive phenomena. Two different approaches have been
adopted, in the framework of post-processing calculations. In the first one,
nuclear rates are varied individually within uncertainties. Ten different
models, covering the characteristic parameter space for these stellar events,
have been considered. The second, somewhat complementary approach involves a
Monte Carlo code in which all nuclear rates are randomly varied within
uncertainty limits simultaneously. All in all, about 50,000 post-processing
calculations, with a network containing 606 nuclides (H to 113Xe) and more than
3500 nuclear processes, have been performed in this work. A brief comparison
between both procedures is outlined together with an overall account of the key
nuclear reactions whose uncertainties have the largest impact in our X-ray
burst nucleosynthesis studies.
