Phase-Resolved Assessment of Helium-Ion-Induced Primary Damage in Nuclear-Facility Concrete Structures

Nuclear-facility concrete structures perform containment, radiation-shielding, and load-bearing functions under prolonged irradiation; however, phase-dependent damage in heterogeneous concrete cannot be adequately represented by a homogeneous-material approximation. This study investigated the effects of the aggregate, cement matrix, and interfacial transition zone (ITZ) on He-ion transport and primary damage. SRIM-2013 calculations were performed for 1–3 MeV He ions, and the phase-resolved displacements per atom (DPA) profiles were combined by volume-fraction weighting and compared with those of an equivalent homogeneous target. At 2 MeV and a reference fluence of 1.0 × 1016 ions·cm−2, the aggregate, cement matrix, and ITZ exhibited DPA peaks of 0.3572, 0.2526, and 0.2749 at depths of 6.0, 7.5, and 9.3 μm, respectively. Increasing the assumed ITZ effective density from 1.47 to 1.89 g·cm−3 reduced the mean projected range, DPA peak depth, and DPA peak magnitude by 22.2%, 22.9%, and 12.8%, respectively. At 2 MeV, the phase-weighted DPA index reached a peak of 0.2237 at 6.0 μm, whereas the homogeneous target produced a peak of 0.3020 at 6.6 μm. Relative to the phase-weighted result, the homogeneous-target DPA peak was 35.0% higher and its peak depth was 10.0% greater. Homogenization therefore altered the primary-damage distribution and obscured deeper phase-specific features. The proposed framework provides phase-dependent initial-damage parameters for multiscale assessment of irradiation-induced degradation in nuclear concrete structures; however, experimental calibration is required before the calculated DPA can be related to material-property degradation or structural performance.