## 6 Summary and Outlook  
A novel modelling approach was proposed and developed to simulate gas dissolution into and diffusion through metals. This was done with the objective of distinguishing between deuterium gas dissolution into/through 316L steel and Pb-Li, since this type of distinction was identified as an issue in static absorption/desorption experiments that attempt to determine the Sieverts' constant of hydrogen isotopes in Pb-Li. This model is considered more accurate than a direct application of [PERSON]'s Permeation Law, since \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Simulation \(\mathcal{D}\)** & **Simulation \(\mathcal{S}\)** & & x/\(x_{f}\) (\%) & & & \(X_{f}\) (mol) \\ \hline
**avg** & [PERSON] [29] & 63.96 & 90.00 & 96.74 & 98.94 & 99.79 & \(2.94\times 10^{-3}\) \\ [PERSON] [20] & **avg** & 73.19 & 87.78 & 93.43 & 96.80 & 99.10 & \(2.59\times 10^{-4}\) \\
**avg** & **avg** & 71.26 & 86.88 & 92.77 & 96.40 & 98.97 & \(2.44\times 10^{-4}\) \\ [PERSON] [10] & **avg** & 55.54 & 83.50 & 92.35 & 96.45 & 99.00 & \(1.89\times 10^{-4}\) \\
**avg** & [PERSON] [35] & 95.71 & 99.64 & 99.82 & 99.92 & 99.98 & \(3.84\times 10^{-6}\) \\ \hline \hline \multicolumn{7}{c}{\({}^{\
icefrac{{1}}{{f_{f}}}}\) (\%)} & 10 & 30 & 50 & 17 & 90 & 100 \\ \multicolumn{7}{c}{Time \(t\) (h)} & 7.2 & 21.6 & 36 & 50.4 & 64.8 & \({}^{\prime}_{f}=72\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Evolution of gas amount dissolved in Pb-Li (\(X\)) at given simulation times (\(t\)), for simulations using same parameter combinations as shown in Figure 14. Dissolved gas amounts in middle columns are given in percentages, calculated in relation to gas amounts at final simulation time step (\(X_{f}\)), for simulations up to \(t_{f}=72\) h.  
the latter can only be applied to steady-state conditions. In contrast, the developed model is able to estimate the dynamics of gas dissolution through metallic barriers both before and after steady-state conditions are reached. The implemented model includes a \"curve-matching\" module. It enables one to determine the dissolution parameters, i.e., the parameters of the Arrhenius functions, for both the diffusivity and Sieverts' constant (solubility) of a gas in a metal. For this, it requires a pressure decrease recorded along time during an experiment using the desired gas-metal pair. This module was used to determine dissolution parameters for deuterium (D\({}_{2}\)) in 316L steel using the Upper Chamber (UC) of the Vacuum Sieve Tray (VST) facility. The curve-matching procedure provided these parameters (reported in Table 2), which were coherent and within the ranges for these values reported in literature. Such results validated the model and its approach, which establishes it as a new asset to address the issue of scattered values for the dissolution parameters of hydrogen isotopes in metals (e.g., steel, Pb-Li). The developed model is also able to take into account interfaces between two metals with different properties. For example, it can be used to simulate a metallic chamber containing a liquid metal. As such, the validated model was subsequently applied to simulate the dissolution of deuterium in the UC containing Pb-Li, as a means of planning for such experiments in the future. This showcases the model's capability to support absorption/desorption experiments, by distinguishing pressure decreases due to dissolution in Pb-Li from losses into/through steel, which are usually neglected. Two improvements were identified to increase model precision. The first one would consist of taking into account the time required to perform the gas injection in the UC. Since the model assumes instantaneous injection, the gas that already dissolves into the metals during the few seconds of injection is not accounted for. The second one would consist of refining the geometrical simplification of the UC by simulating (an) additional channel(s) to represent fittings.