Research For CAD-to-MCNP Conversion Algorithm Based On STEP File

MCNP is a general-purpose Monte Carlo N-Particle code that can be used for neutron, photon, electron, or coupled neutron/photon/electron transport. Specific areas of application include, but are not limited to, radiation protection and dosimetry, radiation shielding, radiography, medical physics, nuclear criticality safety. Because MCNP input files are usually written by hand. Its structure is complex, file is too long, very difficult to describe, and cannot be automated generation. So very easy to make mistakes in the preparation process, work efficiency is low. In order to solve this problem, many organizations and experts put forward their own solutions. One solution is to complete a MCNP auxiliary modeling software and the software include modeling component and convert component, such as Sabrina, MCNP Visual Editor, Moritz, DesignModeler, which can realize MCNP software modeling. But in actual, there are several problems when using the model constructed by these software, like the model cannot be imported into CAD software, difficulty to modify and unable to add materials information. So we need to design a common conversion algorithm to convert the CAD model to MCNP model and solve the defects existing in MCNP auxiliary modeling software. Under this, we design an algorithm of converting CAD model to MCNP geometry model which based on STEP file. STEP standard through a neutral mechanism does not depend on any system, it provides possibility in solving data exchanging and sharing between different CAX systems with an independent property.Based on a large number of Chinese and foreign literature, research and analysis on the related conversion algorithm and conversion software, combined with the study of the solid model, STEP standard and MCNP input file. In according with the surface equations and evaluation of the inclusion relation of shapes, at last using cell tree construction algorithm and complete the conversion from CAD model to MCNP model. To resolve this issue, it provides great convenience during the process of write and produce MCNP input file. This proposed research is promising, and serves as valuable reference for its application in all fields.