Damage metrics

Fold a three-group flux with damage and gas response cross sections and read NRT-dpa, arc-dpa, helium production, and the He/dpa ratio.

Neutron bombardment displaces atoms from their lattice sites and transmutes them into gases such as helium and hydrogen. Two closed-form damage models convert a primary knock-on atom (PKA) energy into a displacement count: the classic NRT model (Norgett, Robinson & Torrens, 1975) and the arc-dpa correction (Nordlund et al., 2018), which multiplies the NRT result by an efficiency below one fitted to molecular-dynamics cascades. Gas production is counted the same way with helium-production cross sections.

The demo below folds a three-group flux with caller-supplied response cross sections, exactly as a reactor dosimetry pipeline would: each group contributes flux × response, and the sum scales with exposure time. All numbers are synthetic round values — no evaluated nuclear data is bundled. The arc-efficiency chart shows the Nordlund correction ξ falling with PKA energy for the material constants you set. The coil section below reuses the same group grid for fast-flux/fluence above your threshold and the weakest-link lifetime across your limit/rate channels. The ratio-UQ block below propagates an uncorrelated relative uncertainty over the flux and both responses through per-draw He/dpa ratios: the reported mean and spread gate against the bias-corrected expectation and the first-order propagated spread at five standard errors, the draw 68% interval gates against the Fieller-construction quantiles (which hold at honestly-sized blocks), and a draw at non-positive dpa fails loudly instead of returning infinity with a spread.

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