  Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the
three evidences for the big bang model, together with the expansion of the
universe and the cosmic microwave background. There is a good global agreement
over a range of nine orders of magnitude between abundances of 4He, D, 3He and
7Li deduced from observations, and calculated in primordial nucleosynthesis.
However, there remains a yet-unexplained discrepancy of a factor 3, between the
calculated and observed lithium primordial abundances, that has not been
reduced, neither by recent nuclear physics experiments, nor by new
observations. The precision in deuterium observations in cosmological clouds
has recently improved dramatically, so that nuclear cross-sections involved in
deuterium BBN needs to be known with similar precision. We will briefly discuss
nuclear aspects related to the BBN of Li and D, BBN with nonstandard neutron
sources, and finally, improved sensitivity studies using a Monte Carlo method
that can be used in other sites of nucleosynthesis.
