Session time out in SAP portal 7.31

Hi Experts,

I am working on SAP portal 7.31. In my portal when the session times out and thus user clicks on the portal then a new session of portal appears in the content area of the previous session.

I want that the new session should open in a new window and previous session gets closed once the session is expired.

Any input on how this can be achieved. Do I need to upgrade any patch or is there any configuration which I am not aware of.Please provide our inputs.

Regards,

Anand