K area emergency water backup studies have been hampered by poor data on flow through the reactor under various emergency conditions. Various tests have been run where emergency conditions have been simulated and flow measurements attempted. In all previous tests, the accuracy of the flow measurements have been questionable. Flow from the high-pressure crosstie can be measured by an orifice in the crosstie, but there has not been any method of measuring the service water contribution to total reactor flow under simulated emergency conditions. One method of measuring the total reactor flow regardless of its source is to determine the relationship between total flow through the reactor and the bottom of riser pressure. After this relationship has been determined for the flow range of interest, then flow to the reactor can be determined by reading bottom of riser pressure (BORP) and converting that to flow. The objective of this production test was to obtain the relationship between BORP and total reactor flow in the range of 10,000 gpm to 25,000 gpm. An additional objective of this test was to check the accuracy of the No. 2 pump discharge venturi.