The blue portal and top of the box appear inside of the box beginning to leave the blue portal itself, this tears the blue portal and causes a secondary portion of it to emerge from itself which I think invalidates the experiment.

If it doesn't, then it continues entering the yellow portal until a depth where the arc of the top of the blue portal that is becoming exposed inside of the box touches the yellow portal for a second time. At that point, a second tear is created and this new tear begins emerging from the blue portal still inside of the box.

This phenomena could reoccur indefinitely if it weren't for the fact that the box would eventually have to open to allow the second instance (the first "image") emerging from the first (real/outermost) blue portal to keep pushing into the first yellow portal. At that point of conflict, the box would open and consequently block further entry into the first yellow portal (real/outermost).

The number of recursions that could occur would depend upon the factor of r_2 / r_1.

A perfect case would be with no box at all, say the blue portal was placed on a moving oval with dimensions equal to itself, then inserted into the yellow portal. In this instance presumably when the emerging blue portal (second portal emerging from first) emerges far enough that it exceeds the smaller radius, it would be exhibiting a number of tears, but it would also collide with the un-portaled wall.

If portals cannot pass through walls, then it collides and inhibits further insertion.