%0 Journal Article %A Amin Abedi and Naser Vosoughi and Mohammad Bagher Ghofrani %D 2011 %J International Journal of Chemical and Molecular Engineering %B World Academy of Science, Engineering and Technology %I Open Science Index 59, 2011 %T An Exact MCNP Modeling of Pebble Bed Reactors %U https://publications.waset.org/pdf/5901 %V 59 %X Double heterogeneity of randomly located pebbles in the core and Coated Fuel Particles (CFPs) in the pebbles are specific features in pebble bed reactors and usually, because of difficulty to model with MCNP code capabilities, are neglected. In this study, characteristics of HTR-10, Tsinghua University research reactor, are used and not only double heterogeneous but also truncated CFPs and Pebbles are considered.Firstly, 8335 CFPs are distributed randomly in a pebble and then the core of reactor is filled with those pebbles and graphite pebbles as moderator such that 57:43 ratio of fuel and moderator pebbles is established.Finally, four different core configurations are modeled. They are Simple Cubic (SC) structure with truncated pebbles,SC structure without truncated pebble, and Simple Hexagonal(SH) structure without truncated pebbles and SH structure with truncated pebbles. Results like effective multiplication factor (Keff), critical height,etc. are compared with available data. %P 1048 - 1052