Simulations and Experiments of Pump Trip Transients in a Mercury Loop at the ORNL Target Test Facility

A transient fluid acoustic model is developed and compared with experimental data obtained from a mercury loop in the Target Test Facility (TTF) at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. The TTF is a full-scale prototype of the Spallation Neutron Source (SNS) target. The target is liquid mercury operating at 100 ^oC and flowing approximately 1440 liters per minute (380 GPM). A loss of power to the mercury pump causes a low-pressure wave to propagate from the pump outlet through the mercury supply lines that may cause vapor to form in the supply lines. The collapse of the vapor cavity gives rise to a pressure pulse referred to as fluidhammer. Fluidhammer was created in experiments at the TTF through a series of induced pump trips. The data gathered from these tests are presented and compared to simulation results. Pressure magnitudes found in trip simulations at normal operating conditions match nearly exactly with those found in experiments, while other trends of the time traces show some good agreement. In general, pump trips simulated at higher pump speeds lead to less agreement with measured data.