The MCNP program is one of the standard nuclear reactor design codes developed by the US government. It works by simulating the tracks of a very large number of particles. Thanks to the the Pacific Northwest National Laboratory (PNNL), we have a rather detailed 3D MCNP model of the ThorCon reactor core and a less detailed model encompassing the entire Can silo.
The drawings give a flavor of MCNP’s view of ThorCon. MCNP has a weird sense of color. The red areas are graphite; purple is the 99/1 graphite hat/plug mixture; dark blue is fuelsalt; yellow is the Pot vessel SUS-316; green is inert gas; pink is borated water; light blue is lead; and the tannish color is concrete.
The MCNP model extends the full height of the silo up to the top of the radtank, and out to the outside of the silo concrete. The PLP, PHX, and primary loop piping are not modeled. The ellipsoidal shape of the Pot top and bottom is not modeled. The Pot lid and bottom are modelled as a disk. The four control rods are modeled as simple, solid cylinders. Currently, each rod must be either fully inserted or fully withdrawn. Currently, the MNCP model can accept only four different temperatures: fuelsalt, moderator, reflector, and pot vessel. However, the core is divided into 9 vertical layers, to allow future modelling of the vertical temperature distribution and intermediate control rod positions. The fuelsalt drain tank is not modelled.