To BPE or not to BPE: neutron tenth-value layers in polyethylene with variable boron content for LINAC shielding

Area of Science:

• Medical Physics
• Radiation Shielding
• Materials Science

Background:

• Medical linear accelerators (LINACs) require effective neutron shielding.
• Borated polyethylene is a promising material, but shielding data is limited.
• Accurate neutron attenuation data is crucial for LINAC shielding design.

Purpose of the Study:

• To systematically quantify neutron attenuation properties of borated polyethylene.
• To determine first and equilibrium tenth-value layers (TVL1 and TVLe) for varying boron content.
• To provide essential data for optimizing medical LINAC shielding.

Main Methods:

• Utilized comprehensive Monte Carlo simulations (n=3504) for neutron transport.
• Modeled polyethylene with 0%, 5%, and 30% natural boron by weight.
• Calculated TVL thicknesses for neutron energies from thermal to 20 MeV, validated with PHITS.

Main Results:

• TVL values varied from 1.3 mm (thermal neutrons, borated PE) to 50 cm (20 MeV neutrons, pure PE).
• Incorporating boron significantly reduced TVL, especially at lower energies.
• The shielding effectiveness of boron decreased around 12 MeV neutron energy.

Conclusions:

• This study provides the first comprehensive characterization of borated polyethylene for neutron attenuation.
• The quantified TVL data supports the design of safer and more efficient medical LINAC shielding.
• Findings will aid in material selection and thickness optimization for radiation protection.