Shrinkage of hollow sphere

Hi, I'm working on diffusion of a hollow sphere (axisymmetric 2D). I have set up the problem for constant external radius and I moved on to the ALE method of simulating the shrinkage of the external dimension (the inner radius is constant). I have a problem setting up the boundary conditions. I attached a pdf file where I explained what BC's I have chosen.

Domain - Free deformation zero initial displacements
Outer boundary - Prescribed mesh displacement (constant displacement in r & z directions)
Axis of symmetry - Prescribed mesh displacement (constant displacement in r & z directions)
Inner boundary - Prescribed mesh displacement (zero displacement in r & z directions)

Any suggestions?

Thanks