how to disable automatic monthly photo stream

OK. I get the concept of Photo Stream. It appears as a separate section in the iPhoto navigation menu.

But iPhoto is also *duplicating* all the photos I import into a month-based "photo stream" which is stored *in my library*.

For example, all the photos I imported this month are duplicated in a "Nov 2012 Photo Stream" album.

This means these photos show up *twice* in my Faces.

I like the iCloud Photo Stream, but I don't want these "hard copy" photo streams being automatically created, and duplicating my photos in my library.

How do I stop that?

Thanks!