New validation case: permeation experiment with FLiBe

[federicohattab]

Reason

Addition of a validation case reproducing an experiment from Calderoni et al. (2008) ( https://doi.org/10.1016/j.fusengdes.2008.05.016).

Design

There are two-layers composite solid structure, where on one side a tritium partial pressure is imposed and on the other side the concentration is null. Of the two layers, one models a nickel plate, where Sievert's law applies, and the other models a layer of stationary molten FLiBe, where Henry's law applies.

The Python script run_val_flibe.py launches the input file val-flibe.i several times changing tritium partial pressure and temperature to reproduce the measurements obtained in the reference.

The reason there is also another input file, val-flibe_test_BC.i, is for debugging purposes only. When using the recently updated InterfaceSoprtion BC in the val-flibe.i input I get a segmentation fault on the first timestep of the simulation. It probably is a machine-specific bug since the same input runs fine on another pc. The val-flibe_test_BC.i input is identical to the original one but uses a different interface kernel and runs fine on my machine.

Impact

New validation case.