Evaluation of Geometric Progression (GP) Buildup Factors using MCNP Codes (MCNP6.1 and MCNP5-1.60)Kyung-O Kim, Gyuhong Roh and Byungchul LeeEPJ Web of Conferences, 106 (2016) 03009DOI: https://doi.org/10.1051/epjconf/201610603009