Depends upon what you mean by xray machines. You can send both develeoped and undeveloped film through security in your carry on unless it is higher than 800 speed. I have done this many times and have had no problems. I have even sent the same film through multiples times (went to NYC and your bags are xrayed at the statue of liberty and the empire state building - so, in addition to being xrayed twice at the airport, they were also xrayed twice in NYC - a total of 4 times - NO problem - the pics were excellent quality.
Now, if you're talking about the xrays they use on checked luggage - they will ruin your film whether it is exposed or not.
Jamee