Figure 7.
The graph depicts pressure change in vessel A 21 in megapascals on the y-axis versus elapsed time in days on the x-axis, ranging from 0 to 150 days. Measurement data are shown as triangular markers, starting near 0 megapascals and decreasing to around negative 0.015 megapascals by about 45 days, followed by relatively stable values with short, sharp drops near 45, 95, and 105 days. A solid line labelled based on lab-measured D e model shows a smoother decline to approximately negative 0.02 megapascals and deeper transient drops at the same times. A dashed line labelled 0.8 D e model closely follows the measurements, stabilising near negative 0.015 megapascals after 50 days with smaller transient drops aligned with the measurement events.Results of Phase 1 – helium in-diffusion test. The figure shows the measured pressure drop (black symbols), modelled results based on laboratory-measured diffusion coefficients De (red lines), and modelled results using best-fit diffusion coefficients (blue dashed lines)