[en] This paper presents the process of developing the relationship model between gap and overlap in the design of the bunker lead door. This involves studies of the relationship between gap and overlap design ratio and the dose rate angular effect based on source position. The model was developed by using Particle and Heavy Ion Transport Code System (PHITS) simulation software. The developed relationship model is an accelerated assist tool to determine the acceptable ratio of gap and overlap in the design of radiation facility based on the attenuation method. (author)