A Jomablue Survey can be submitted only once per person, per survey. The URL that is automatically created for each attendee tracks who is answering the Survey and therefore marks them as 'Responded' to the survey.
If a user attempts to reload or follow the link to the survey for a second time, they are presented with the following message.
"You have already completed this Survey"
Once a Survey has been submitted, there is no way to "undo" the submission as a User or Administrator.