Determine the permeation reduction factor (PRF) of the Al2O3 coating for hydrogen isotopes

Determine the permeation reduction factor (PRF) for hydrogen isotopes (H2 and D2) of the ~250 μm thermally sprayed Al2O3 coating applied to the Ni-200 permeation cell in the HYPERION facility over the operating temperature range 773–973 K, so that the intrinsic permeabilities of Ni-200 and molten FLiBe (2LiF–BeF2) can be resolved without reliance on bounding assumptions.

Background

In the HYPERION experiments, the permeation cell is externally coated with ~250 μm Al2O3 to ensure structural integrity at high temperature. However, the hydrogen-isotope permeation reduction factor (PRF) of this coating under operating conditions is not known.

Because the PRF is unknown, the authors analyze results using bounding cases (PRF = 1 and PRF → ∞) to bracket the intrinsic permeabilities of both Ni-200 and FLiBe. Establishing the PRF would remove this bounding uncertainty and enable direct determination of intrinsic permeabilities.

References

Since the Q2. Permeation Reduction Factor (PRF) for the Al2O3 coating applied on the permeation cell is not known a priori, the permeability estimations for Ni and FLiBe are reported within the bounds of unity and infinite PRFs.

— Permeation behaviour of hydrogen isotopes in molten FLiBe (2LiF-BeF2): Identifying sources of uncertainty and associated measurement challenges  (2603.28991 - Saraswat et al., 30 Mar 2026) in Section 2.1 (System design description)