The Federal Reserve investigated how it could keep a massive short term lending market from freezing up if America defaulted on its debt, according to a person familiar with planning that was done by the New York Fed. The person, who asked not to be identified, told Reuters on Tuesday that officials researched whether they could lend support to the triparty repo market, which is one of the pillars of short-term lending on Wall Street. The comments follow the revelation on Monday that congressional staff had seen documents on the Fed’s planning for how to manage a sovereign debt default.