I had surgery to remove deep abscess on breast , surgeon removed a golfsize amount and has ordered to irrigate wl/hydrogen poraxide, is that safe?

Yes: Follow the post-op instructions to avoid it coming back. The key to drainage is to get the concentration of infection and allow continued drainage to promote the healing process. They want it to heal from the inside out. Hydrogen peroxide is fine and safe.

Safe, yes. Benefit??: Hydrogen peroxide has been a popular solution for treating wounds due to its purported antimicrobial effects and it's bubbling action, which may help debride a wound. Unfortunately, studies have not supported the antimicrobial effect and it may actually slow down healing. Regardless, it is safe and I am certain that your surgeon has had success with this technique.