Real-world challenges often involve complex phenomena, spanning multiple physics domains, including thermal, mechanical, hydraulic, electrical, radiative, chemical, and others. To grasp the intricate interactions across multidisciplinary fields, our goal is to devise a multiphysics computational framework for simulating, modeling, and analyzing those complex real-world phenomena. This framework will facilitate our comprehensive understanding of the underlying physics.
EXAMPLE 1: VOID FRACTION OF COOLING WATER ON MEDICAL ISOTOPE PRODUCTION TARGETS
A gaussian beam distribution was specified in MCNP with a series of transformation cards to replicate the ring-shaped rastered production beam profile (Fig. 1). Volumetric heat deposition within targets A, B, and C generated by the proton beam was extracted from the MCNP model and used to obtain the heat flux distribution on each target capsule surface in contact with the cooling water. Coupled with CFD subcooled flow boiling modeling, void fraction distribution was obtained as a function of the heat flux distribution and channel inlet velocity profile (Fig. 2). The maximum predicted void fraction is 0.83, forming on the backside of the target B, where the highest proton beam power is deposited.
Fig. 1. MCNP Geometry consisting of the vacuum beam line, beam window, isotope production targets A, B, and C, target capsules, cooling water domain, and target holders & frames.
Fig. 2. Void fraction distribution calculated by coupling the MCNP radiation transport and ANSYS CFX subcooled flow boiling model.
J. H. Seong, J. Morrell, B. Singh, K. Woloshun, E. Olivas, P. Lance, N. Kollatrik, E. O'Brien*, c. Vermeulen
Development of experimental and computational frameworks to predict subcooled flow boiling in the LANL Isotope Production Facility
International Journal of Heat and Mass Transfer (IJHMT), 203, 123836
EXAMPLE 2: EVALUATION OF Mo-99 PRODUCTION LIQUID METAL TARGET DESIGN
Fig. 3. Niowave Inc.'s Mo-99 production system.
Niowave Inc. uses an electron accelerator to irradiate a neutron source converter embedded in an uranium assembly where Mo-99 is produced by fission reactions (Fig. 3). The neutron converter is designed to have a stainless steel (SS) housing surrounding lead-bismuth-eutectic (LBE) flow, where neutron is generated by photonuclear reactions. The heat deposited on the irradiated LBE target and SS housing is removed through forced convection. At high incident electron beam power, high fidelity simulation is essential to ensure the in-beam survival and integrity of the system.
(Fig. 4) The design of the converter was optimized by 2D/3D hydraulic analyses using ANSYS Fluent volume-of-fluid model to obtain LBE velocity under limitation with a favorable pressure gradient. Attila4MC was used to import a customized SolidWorks geometry of the discrete LBE, vacuum, SS volume and to generate unstructured meshing for MCNP. 3D volumetric heat deposition profile obtained by MCNP was mapped into CFD, enabling high-resolution 3D multiphysics analysis. Conjugate heat transfer analysis was performed to obtain the 3D temperature profile for the LBE and SS. Results indicated that there are no issues of LBE cavitation & evaporation, nor severe erosion & corrosion on LBE-SS interface (Fig. 5).
Fig. 4. Multiphysics computation scheme.
Fig. 5. Evaluation of LBE windowless target design; 3D profile of volume fraction, velocity, pressure, total particle flux, heat deposition, and temperature.
J. H. Seong, R. Kong, K. Woloshun, B. Singh, E. Olivas, T. Grimm, R. Whalen
Multiphysics analysis of LBE windowless target design under high-power electron beam
8th High Power Targetry Workshop (HPTW23)
34141 대전광역시 유성구 대학로 291 (구성동 한국과학기술원 373-1) 기계공학동 www.kaist.ac.kr