Review of the nat C(n, γ) cross section and criticality calculations of the graphite moderated reactor BR1

•Review of the experimental and evaluated data for natC(n,γ) and 12C(n,γ).•Comparison of ENDF/B-VII.1 and JEFF-3.1.2 within BR1 criticality calculations.•The thermal capture cross section is of importance in large graphite-systems like BR1.•The 12C(nth,γ) given by Firestone and Révay (2011) is recommended to be used.•The JENDL-4.0 evaluation takes the latest experimental data available.