Primordial or Big Bang nucleosynthesis (BBN) is one of the three strong evidences for the Big-Bang model together with the expansion of the Universe and the Cosmic Microwave Background radiation. In this study, we extend the nuclear network until sodium, to evaluate the primordial CNO abundance that could affect Population III stellar evolution. The complete network includes more than 400 reactions, out of which ≈270 reaction rates were calculated using the TALYS code. We performed a

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... study to identify the important reactions for CNO nucleosynthesis. We note the stability of results on Big Bang nucleosynthesis CNO production compared to previous works: CNO/H = (0.5 − 3.) × 10 −15 .