Unfortunately, you cannot have the url of the iframe display in the main url bar.
I see what you mean by no SEO
value (which is why you should avoid iframes for pages you want to optimize in the first place
). What exactly is your goal here, or specifically: what are you trying to accomplish by using the iframe. If it's your subdomain, couldn't you just put the main page layout (with the navigation, etc...) on the survey. subdomain web-pages?