June 23 (Reuters) - Volume in the U.S. Federal Reserve"s reverse repurchase operation reached a record $813.573 billion on Wednesday as financial institutions continued to pour cash into the overnight facility. The daily operation, which included 73 bidders, was up from $791.6 billion on Tuesday. While volume has been building since March, it grew further after the Fed last week raised the rate it pays on reverse repurchase agreements to 0.05% from 0% as part of technical adjustments to keep the benchmark effective fed funds rate from falling too low.