An integrated effort by the Versatile Test Reactor (VTR) Gas-Cooled Fast Reactor (GFR) Team to develop an experiment vehicle or extended-length test assembly for the VTR experiments is led by the Idaho National Laboratory and supported by an industrial partner, General Atomics, and university partners, including Texas A&M University, University of Michigan, Oregon State University, University of Houston, and University of Idaho. The overall focus of the effort is to design a helium gas-cooled cartridge loop (GCL) to assist with the testing of fuels, materials, and instrumentation to further support development of advanced reactor systems. This study is divided into two parts. Part I provides the GCL functional requirements and critical irradiation data needs for advancing GFR technologies. Part II includes the measurement techniques developed to measure the thermophysical properties of the different materials in the GCL, as well as the functionality and efficacy of these instrumentation and control systems within the GCL.

This paper, Part I, describes the overall preliminary conceptual design of the VTR helium cartridge loop, the design of a fission product venting system, the thermal-hydraulic effects of flow direction, and gamma-heating generation in the cartridge. This paper also describes a three-dimensional computational fluid dynamics study that was carried out to examine the effects of the helium flow direction in the GCL on its thermal-hydraulic characteristics, engineering feasibility, and in-VTR experiment design. Both steady-state operation and a transient scenario (pressurized loss of forced circulation) were analyzed for the upward and downward helium flow options in the test article section in the GCL to provide quantitative data for selection of the helium flow direction. Additional analyses and development, as well as integrated out-of-pile testing, are planned to demonstrate and verify the performance of the GCL prior to insertion into the VTR.