Can stainless steel pans be kashered after unclean meat has been cooked in them?
Yes, pans (non teflon-coated) can be kashered by immersion in boiling (bubbling) water.
Clean the pan well and wait a 24 hour period.
Boil a large pot of water (a small amount of soap can be added to the water), and immerse the pan inside.
This is sufficient to kasher a pan where the meat was cooked in liquid.
If the meat was cooked without liquid, a process of libbun will be required: Put the pan on an open flame until both inside and outside are hot enough to singe paper.