Yes, you can have a Other Direct Cost CLIN in a fixed priced contract, assuming it is only for travel. Contract type determinations are made at the CLIN level.    Remember, Any contract that has a CR CLIN for something more than just for travel reimbursement will be identified as a CR contract for contract action reporting purposes. See FAR 4.1003(e ), and DFARS 204.7103-1 (c) , which states " (c) For a contract that contains a combination of fixed-price line items, time-and-materials/labor-hour line items, and/or cost-reimbursement line items, identify the contract type for each contract line item in Section B, Supplies or Services and Prices/Costs, to facilitate appropriate payment."   

Based on the information provided, the travel costs should be ODC.