Normally, in the flow of a flashing liquid through a pipe, it is assumed that the location of the choking phenomenon, if it exists, is at the exist of the pipe. Experiments have indicated that thee are circumstances under which choking can occur at the entrance instead. These experiments were performed to study the flashing of initially-compressed water through short lengths of pipe with length/diameter ratios of up to 20. Entrance configurations considered included sharp and rounded transitions and conical passages of 20- and 45-degree tapers. Upstream pressure ranged from 115 to 1,800 psia and in all instances, the upstream pressures were much greater than the saturation values. In most cases, choking of the flow was incurred when the liquid entering the pipe was required to depressurize to the saturation pressure (or below) when accelerating through the reduction at the entrance. Axial pressure surveys demonstrated that the pressure at the entrance of the pipe during choked conditions was the saturation pressure. It remained at the saturation value regardless of upstream pressure and the pressure distribution along the remainder of the pipe.

On February 16, 1963 Production Test IP-573-1 was conducted at the K reactors to provide data to revaluate the adequacy of the last-ditch crosstie system. This test was run subsequent to rigorous mechanical cleaning of the crosstie system piping (January 9, 1963); therefore the resulting data reflects essentially clean line conditions. On November 1, 1963, approximately 8-1/2 months after the above-mentioned tests, a series of steady-state tests were conducted under authorization of Production Test IP-628-I. These tests vere designed to accomplish four major objectives: To evaluate the change in flow capability,of the crosstie system since the last test series; to test the ``worst case of crosstie flow capability. (This vas not run in February); to obtain hydraulic data pertinent to a proposed Modified Secondary System; and to obtain pressure drop and flow data on the crosstie system during flushing in order to revaluate the system adequacy, i.e., capacity, at a later date by comparing flushing data. This report contains the numerical results of the pressure and flow data obtained during these tests.

The primary object of the C2 tests for the NRX- A reactor support system is to survey the capabilities of the structure.

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