Feb 13 - Fitch Ratings expects to rate Discover Bank's (a wholly owned subsidiary of Discover Financial Services, with a long-term Issuer Default Rating of 'BBB') senior unsecured notes 'BBB'. The notes are expected to mature in 2018. Issuance proceeds are expected to be used for general corporate purposes. Fitch expects Discover to be an opportunistic issuer of bank notes over time, which will serve to enhance the company's funding flexibility. KEY RATING DRIVERS Discover's Stable Rati