Monte Carlo Analysis of Radiation Shielding and Damage in Multi-Layer HDPE Shields
Abstract
In this study, a functionally graded two-layer HDPE composite shield was designed, and its efficacy against secondary space radiation was evaluated using Monte Carlo simulations. The design, combining a neutron-absorbing front layer (6LiH/B2O3 doped) and a gamma-attenuating secondary layer (BiTaO4 doped), significantly outperforms single-layer structures. GEANT4 simulations show that while the front layer efficiently absorbs neutrons, it generates secondary gammas, which are subsequently attenuated by the secondary layer—achieving up to an 85% reduction in the epithermal neutron energy range. FLUKA analyses highlighted a trade-off between shielding and durability: the front layer sustained intense damage (approx. 1200x DPA and 500x TID vs. pure HDPE) due to (n,α) reactions. However, this damage was confined to the first 0.5 cm, preserving the secondary layer's integrity. Consequently, the multi-layer design successfully mitigates primary neutrons and secondary radiation while localizing material degradation.
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