Yes, with no or very, very minimal risk.
First, plagiarism is an academic integrity issue, not a legal problem. It is copyright that you would worry about - except do not worry. You would be copying yourself which, I assume, you give yourself permission to do.
If your previous application was owned by an employer, not you, then that doesn't apply. But, people often copy boilerplate language from and others' applications.
From a Wikipedia entry on exactly this topic
The website of the United States Patent and Trademark Office states that "the text and drawings of a patent are typically not subject to copyright restrictions," and similar views have been published by patent attorneys. As one unpublished academic working paper on the topic of copyright application to patents notes, however, there is no law exempting U.S. patents from copyright, but there is also almost no published literature or case law on the topic.
See that entry for information relating to other county's laws and practices.