[NRL Employee's Claim for Per Diem]

A Navy employee claimed reimbursement for per diem expenses incident to temporary duty he performed near his permanent duty station. GAO held that the: (1) original travel orders authorizing per diem allowances was within the Navy's discretion and could not be revoked or modified retroactively; (2) claimant was not indebted to the Navy for the amounts it reimbursed him; and (3) claimant was entitled to reimbursement for his travel expenses. Accordingly, the claim was allowed.