A Magneto-Hydrodynamic System for Generating High-Pressure Impluses in Spallation Targets

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) produces neutrons for neutron scattering studies that allow researchers to study key materials properties. These neutrons are produced by the interaction of a very short (1 µsec), highly intense (1 MW at 60 Hz) pulse of protons within a flowing bath of mercury, in a process that deposits a large amount of thermal energy in the mercury. Because mercury has a high coefficient of thermal expansion, a high-amplitude (~38 MPa) short-duration (1 µsec) pressure pulse is created, which causes erosion damage to the mercury target assembly, impacting SNS target lifetime and operating costs. What is needed is a way to generate representative pressure pulses outside the SNS facility, in order to evaluate proposed erosion mitigation strategies. This project will develop a facility, based on magneto-hydrodynamic (MHD) pulse generation, capable of producing pressure pulses of similar magnitude and rise time to those experienced in the SNS. In Phase I, a pilot-scale facility, capable of producing such pressure pulses and rise times, was developed. The pressure pulses created in liquid mercury exceeded 1.4 MPa, with rise times under 5 µs and a repetition rate greater than 0.4 Hz. Phase II will design, fabricate, and characterize a 2nd-generation, full-scale current pulse generator that will accurately simulate the SNS target environment. Commercial Applications and other Benefits as described by the awardee: In addition to providing immediate assistance to the SNS for the mitigation technology of erosion damage, the technology developed on this project should impact any system in which high-pressure, short-duration, and high pulse frequency impulses are present, including industrial applications involving water hammer and other flows that include cavitation