Seems unlikely that TSA would want to open sealed envelopes unless something in them were to show up as an "anomaly" on the xray. Even if you're carrying 50 copies of a three-page résumé you've got less than one-third of a ream of paper. Doubt they'd even notice the presence of those envelopes at all when your (preferably locked) carry-on bag goes through the xray.

That said, even if TSA were to demand a look at your materials, the fact is that you should NOT be including any truly confidential information in the first place. The reality is that your résumé or CV is being handed over to a bunch of strangers, especially at a job fair, and once it's in their possession, you have absolutely no assurances that it will be adequately protected. In most organizations, multiple people will be handling and reviewing your CV/résumé, sometimes passing it around to all members of a department, emailing or faxing it to other offices, leaving it lying around on desks, etc. You also have no way of knowing that it will be properly disposed of if you're not considered as a possible candidate. This means that no sensitive information should be on the actual CV itself (residence address, social security number, salary history, driver license number, date of birth, etc.). These data can and should be supplied separately on an as-needed basis.

Can you explain why a "professional broadcaster" would regard his/her demos as confidential? If, by definition, your job is to communicate with as many members of the public as you can possibly reach, why are samples of you doing so private?

Of course, if you're really and truly worried about it, agree with the previous suggestion of printing it when you get there, or using FedEx.