From MEI, re: a question whether HDR students can submit work via Turnitin.
It is slightly murky because there are conditions in the Turnitin
License that stop academics from using it to check things they are
wanting to publish.
I think that as long as we can say that this is related to their studies, it is ok. [Later reply noted that manuscripts for publication that form part of a thesis can also be submitted, as they are considered primarily for assessment].
You would mainly just need to remember to set up Turnitin so that it is not storing submissions to the Turnitin repository.