“…Therefore, if Monte Carlo codes are to be realistically used for whole core analysis and design, the optimization of geometry navigation should be investigated further. To the author's knowledge, several classical optimization techniques such as neighbor search method (Forrest, 2005;She et al, 2011), multi-level geometry hierarchy method (Donovan and Tyburski, 2006;Geant4 Collaboration, 2009), bounding box method Wang, 2006) and delta-tracking method (Leppanen, 2010;She et al, 2011) have been widely used in many codes to improve geometry navigation performance. And recently, another new technique named geometric template was introduced by MC21 to enhance its geometry navigation for large-scale whole core realistic models.…”