An improved photo-absorption cross section model for the physics models regime in MCNPX

Area of Science:

• Nuclear Physics
• Computational Physics
• Particle Physics

Background:

• The CEM2k model in MCNPX is crucial for simulating photo-nuclear reactions.
• Existing models relied on free nucleon cross-sections, limiting accuracy for complex nuclides.
• Accurate modeling is essential for applications like radiation shielding and detector design.

Purpose of the Study:

• To improve the accuracy and predictive power of the CEM2k photo-nuclear physics model in MCNPX.
• To incorporate experimental photo-absorption cross-sections and isotope-specific data.
• To enhance the simulation of photo-nuclear processes, particularly in the giant dipole resonance region.

Main Methods:

• Photon transport was improved above 100 MeV using experimental photo-absorption cross-sections of nuclides.
• Below 100 MeV, isotope-specific giant dipole resonance (GDR) photo-absorption cross-sections were implemented.
• Photo-fission cross-sections were adjusted to align with the BOFOD evaluated data.

Main Results:

• The enhanced model shows improved accuracy for photo-nuclear reactions across a wider energy range.
• The model can now supplement MCNPX's tabulated data for isotopes with missing evaluations.
• Predictive power is significantly enhanced, especially above GDR resonances and in the GDR region.

Conclusions:

• The improved CEM2k model offers more reliable simulations of photo-nuclear interactions.
• This advancement is vital for accurate predictions in areas lacking comprehensive experimental data.
• The updated model enhances the utility of MCNPX for nuclear physics research and applications.