Abstract: Exampled by the spent fuel pool of TNPS which is consist of 2×5 fuel storage racks, the spent fuel high-density storage based on burnup credit (BUC) and related criticality safety issues were studied. The MONK9A code was used to analyze k_eff of different enrichment fuels at different burnups. A reference loading curve was proposed in accordance with the system k_eff’s changing with the burnup of different initially enriched nuclear fuels. The capacity of the spent fuel pool increases by 31% compared with the one that does not consider BUC.