Sunriser,
There are 2 conflicting statements from you, in initial post you said
we generate scrap by confirming it against a process order
Now you are saying
This all scrap are unexpected scrap, this are not coming from production process
Unless you give us clarity on how your business generating scrap then it is not an easy one to suggest the options.
In SAP you can generate scrap in multiple ways during production process you can refer this document for same Different Scraps and their effects in SAP PP
For scrap sale order cycle you can refer this document http://wiki.scn.sap.com/wiki/display/ERPLO/Scrap+Sales+Order+Cycle
BR
KK