IRS deems per diem taxable after being in a 50 mile radius for a year
I believe you're misreading that. The GSA (for the entire Government) and the IRS apply a 50 mile radius, but that standard is for reimbursing their employees for travel costs. It has nothing to do with tax law and when reimbursements are taxable.
It is my understanding of IRS code that per diem is taxable if I am in an area for 1 year
Not quite. Perdiem is taxable if, when the engagement begins, you are reasonably expected to be there for more than one year, even if the assignment ends early. If, for example, you anticipate it to be a permanent assignment but it ends in three months, the perdiem is taxable because you
expected to be there more than one year.
As Bill indicates, there is also a problem with continuous traveling, resulting in no tax home, and as a consequence no tax free perdiem. You should take the time to read the two paragraphs under
What is an ?IRS Tax Home?? at this site ( http://www.travelnursing.org/understanding-your-travel-nurse-pay-package/ ) which is written specifically for traveling nurses.