How to generate crystal models with radial grain size gradients?

[Pen0516]

Dear sir，
Can Neper generate crystal models with radial grain size gradients? If possible, how should it be generated?
For example，how can I generate the crystal model that the grain size near the center of the circle is larger, while the grain size gradually decreases away from the center of the circle.
I really appreciate any help or suggestions you can offer. Thank you in advance for your time and support!