Open Access
Table 3
Release criteria, steady-state post-release gas pressures in grain face bubbles, and relaxation times for the considered release mechanisms for grain boundary gas. 
is the critical bubble gas pressure for grain boundary rupture and υ is a constant model parameter less than unity; see below.
| Post-release | Relaxation | ||
|---|---|---|---|
| Mechanism (i) for grain | Criterion for | gas pressure, | time [s], |
| boundary fission gas release | gas release |  |
τi |
| (1) Bubble interconnection | ϕ2 ≥ 0.48 | Ph + Ps | 2 |
| (2) Grain boundary rupture |  |
 |
0 |
| (3) Grain boundary microcracking |  |
 |
2 |
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