Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes

Area of Science:

• Space radiation physics
• Radiation transport simulation
• Astrophysical phenomena

Background:

• Solar Particle Events (SPEs) pose significant radiation hazards in space.
• Accurate modeling of particle transport through shielding is crucial for astronaut and equipment protection.
• Comparison of different radiation transport codes is essential for validating simulation accuracy.

Purpose of the Study:

• To analyze the transport of SPEs through aluminum and water shielding.
• To compare the results of Monte Carlo (MC) codes (MCNPX, PHITS) with a deterministic code (HZETRN via OLTARIS).
• To evaluate particle spectra, fluence, dose, and dose equivalent behind shielding.

Main Methods:

• Utilized MCNPX 2.7.0, PHITS 2.64 (MC codes), and OLTARIS v3.4 (deterministic code).
• Simulated four historical SPEs with varying aluminum (10-20 g/cm²) and water (30 g/cm²) shielding.
• Calculated differential particle spectra (protons, neutrons, photons), total fluence, dose, and dose equivalent.

Main Results:

• All codes showed good agreement in particle fluence spectra.
• MC codes (MCNPX, PHITS) demonstrated closer agreement with each other than with OLTARIS.
• Oltaris reported lower neutron fluence at energies below 100 MeV compared to MC codes.
• MCNPX and PHITS results showed better agreement with OLTARIS for fluence, dose, and dose equivalent based on mean square difference.

Conclusions:

• Monte Carlo simulations (MCNPX, PHITS) provide reliable predictions for SPE transport through shielding.
• Oltaris (HZETRN) is a viable tool, but discrepancies in neutron fluence at lower energies warrant attention.
• Code intercomparison is vital for enhancing the accuracy and reliability of space radiation assessments.