Helical-Cruciform Fuel model generator for MCNP

1. Use the python script to generate the HCF model for MCNP automatically.

2. Whole post-data extraction and plotting.

3. This python script was used in High-fidelity neutronics and thermal-hydraulics analysis of helical cruciform fuel based on small modular FHR, Prog. Nucl. Energy 159 (2023) 104633.