Cleanwipe cannot be run in silent mode.
Please review the article by Symantec's Chetan Sevade:
https://www-secure.symantec.com/connect/articles/new-cleanwipe-version-introuduced-sep-121-ru2
And the comment by Symantec's Mithun Sanghavi:
https://www-secure.symantec.com/connect/forums/cleanwipe-12120152015-no-silent#comment-8490741