Session: FSI-05-01 International Symposium on Emerging Technologies

Paper Number: 60940

Start Time: Tuesday, July 13, 2021, 08:00 PM

60940 - Sensitivity Analysis of Tunable Equation of State Material Model In Pulsed Mercury Target Simulation 

A pulsed neutron spallation target is subjected to very short but intense loads from repeated proton pulses. The target modules receive sixty pulses of 1 GeV protons each second. Each pulse is approximately 0.7 microseconds long and carries 23.3 kJ of energy for a time-averaged power of 1.4 MW. Approximately 60% of the energy from the proton pulse is deposited into the mercury target material and the stainless-steel target structure. The deposited energy leads to the creation of a high-pressure region in both the stationary target structure and the flowing mercury. The high-pressure propagates and leads to fluid-structure interaction. The resultant loading on the stainless-steel target structure that contains mercury fluid is difficult to predict. Different simulation approaches and material models for the mercury have been tried. To date, the best match of simulation to experimental data was obtained by using an equation of state (EOS) material model with a specified tensile cutoff pressure, which simulates the cavitation threshold [1]. The inclusion of a threshold to represent cavitation was a key parameter in achieving successful predictions of stress waves triggered by the high energy pulse striking the mercury and vessel. However, recent measurements of target structure strain show that significant discrepancies between the measured strain and simulated strain values with the EOS mercury model still exist. These differences grow when non-condensable helium gas is intentionally injected into the flowing mercury to reduce the loading on the structure. An EOS based proportional–integral–derivative (PID) mercury model was proposed to reduce the gap between the measured and simulated vessel strain responses for targets with gas injection. The conceptual and numerical description and initial investigation of the PID model were presented in previous work [2]. Further studies of this PID model, including the sensitivity of the structure’s strain response to model parameters (the tensile cutoff, proportional–integral–derivative parameters K_p, K_i, and K_d) are reported in this article. Results show that the strain response is more sensitive to changes of the tensile cutoff value than to changes in the model parameters K_p, K_i, and K_d. These results will aid in future work where the model parameters will be optimized to match simulation data to strain measurements.

Presenting Author: Lianshan Lin Oak Ridge National Laboratory

Authors:

Lianshan Lin Oak Ridge National Laboratory
Drew Winder Oak Ridge National Laboratory