Results 1 - 8 of 8
Results 1 - 8 of 8. Search took: 0.016 seconds
|Sort by: date | relevance|
[en] The Global Nuclear Energy Partnership (GNEP) is proposing to develop a sodium-cooled fast-spectrum reactor (SFR) to transmute and consume actinides from discharged nuclear fuel. To meet performance objectives, new and advanced fuels and targets need to be developed. The fuels to be irradiated include metal and oxide mixed actinides (U-Np-Pu-Am-Cm); for the target concept, Am-Cm has been considered. A significant part of the development process is the irradiation of the fuel and cladding in a prototypic fast reactor environment to determine the performance under irradiation. Analysis results are presented in this paper for a fast-neutron irradiation facility design based on the large fast neutron flux available in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) combined with the use of a strongly-absorbing thermal neutron shield. Several designs were assessed; the preferred concept consists of a three-pin design with an europium oxide thermal neutron shield, to be situated in the HFIR flux trap. Analyses show that this design could provide a fast to thermal neutron flux ratio greater than 400, a fast neutron flux larger than 1x1015 n/cm2.s, and with an acceptable impact on HFIR operation. This design feasibly will be a relatively low-cost near-term facility that meets the requirements for fast fuel irradiation. (authors)
[en] A new experimental facility is being developed for materials irradiation and testing at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR). Details of this facility have been presented before. A prototype of this facility, the Thermosyphon Test Loop (TSTL) has been built, and experimental data have been obtained and analyzed. Pretest calculations for this facility with the RELAP5-3D code have been presented previously as well as other calculations with the TRACE code. The results of both codes were very different. RELAP5-3D predicted much higher pressures and temperatures than TRACE. This paper compares calculated results with the TSTL experimental data. Comparison of calculations with the codes RELAP5-3D and TRACE with experimental data of the new TSTL facility has shown that TRACE results agree well with the data and that RELAP5-3D calculates very high pressures and temperatures. The TRACE code is well suited to model this facility and is being used for future calculations. (authors)
[en] A new experimental facility is being developed for materials irradiation and testing at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR). Details of this facility have been presented before. A prototype of this facility, the Thermosyphon Test Loop (TSTL), has been built, and experimental data have been obtained and analyzed. The purpose of the tests was to establish a safe operating envelope for actual fueled experiments in a HFIR experimental facility. Both steady-state and transient experiments were conducted. The data will also be used to validate computer simulations of the thermosyphon so that those codes can be used for future safety-basis calculations. This paper presents a summary of the TSTL experimental data and analysis. A report with all the data and analyses will be published in the near future. Experimental data from 51 tests in the TSTL have been obtained. This extensive set of high quality data can be used to benchmark codes with boiling and condensing phenomena. This new proposed irradiation facility allows materials to be irradiated without concern for HFIR coolant contamination (from specimen failures) as it uses a separate coolant, that is isolated (except thermally) from the HFIR primary coolant. (authors)
[en] The use of hydraulic rabbit capsules inserted into and ejected from the core of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) during full power operation allows for precise control of the neutron fluence in fueled experiments. Rabbit capsules with strong thermal neutron absorbers must be used to screen out thermal neutrons, thereby reducing the heat generation rate while maintaining the fast neutron flux that produces displacement damage similar to fast reactor type conditions. However, rapid insertion and ejection of rabbit capsules containing a strong neutron absorber causes a reactivity response in the reactor that has the potential to engage the HFIR safety response system which could result in an unplanned shutdown. Therefore, a set of tests were performed to provide the data needed to establish limits on the reactivity worth that can be ejected from the hydraulic facility without causing a reactor shutdown. This paper will describe the design, operation, and results of the reactivity measurements undertaken to understand the reactor response to insertion of the gadolinium-lined rabbit capsules. (author)
[en] The Material Irradiation Facility (MIF) at the Oak Ridge National Laboratory (ORNIL) High Flux Isotope Reactor (HIFR) controls and monitors instrumented irradiation experiments for materials and fuel research. In 2013 ORNIL founded a Laboratory Directed Research and Development project to reinvigorate the use of instrumented experiments by redesigning MIF to enhance its capabilities. MIF improvements include an updated and more sophisticated experiment monitoring system, a modular design allowing easier addition of simultaneous experiments, and features that allow rapid incorporation of additional instrumentation Interest in materials and fuel irradiation has increased significantly over the last decade. Much of this interest is related to investigating the performance of advanced materials for fusion environments, designing and developing improved fuel and cladding materials, and examining material characteristics and behavior under irradiation conditions. At ORNL, the irradiation engineering team has more than 60 years of experience designing and fabricating various types of irradiation experiments. Rabbit capsule experiments are small scale and relatively inexpensive. These capsules are typically designed to be irradiated in the flux-trap region of the core. Full-length target capsules are larger scale and could be either instrumented or non-instrumented. These more complicated capsules can be irradiated in any of the experiment facilities at HFIR. Instrumented experiment irradiation provides significant advantages for researchers. The unique advantage is that the researcher can monitor and acquire in situ data and change capsule operating conditions in real time during the irradiation. This capability enables tight control of desired experimental conditions so that they match the design specifications throughout the irradiation. Also, the experiment conditions (e.g., temperature and pressure) can be altered during the test, enabling significant flexibility and the ability to collect considerably more data from a single experimental capsule. This capability allows measurement of a variety of material properties (conductivity, fission product composition, etc.) that otherwise would only be available upon post-irradiation examination, where non-equilibrium conditions brought on by irradiation do not exist. The data generated by these experiments contribute significantly to the understanding of material behavior under irradiation. MIF is an experimental platform that can host fully instrumented and monitored experiments in a high neutron flux environment. Its primary functions are to provide clean inert gas (helium, neon, argon) to experiments at controlled pressures and flows, monitor irradiation conditions (typically temperatures and pressures) during irradiation, and monitor effluent gases from experiments. This facility allows monitoring of chemical processes during a fueled irradiation, where this becomes important for detecting fuel failures. This paper reports the efforts towards reestablishing the value of HFIR for instrumented irradiation experiments and the improvements to MIF that ultimately reduce the costs of instrumented irradiation. This project advances ORNL materials capabilities to new levels by providing a state-of-the art, robust and flexible facility that can be expanded as customer requirements change, while supporting the goals of the fusion, advanced fuels, and structural materials programs. (authors)
[en] Swelling, or volumetric expansion, is an inevitable consequence of the atomic displacement damage in crystalline silicon carbide (SiC) caused by energetic neutron irradiation. Because of its steep temperature and dose dependence, understanding swelling is essential for designing SiC-based components for nuclear applications. In this study, swelling behaviors of monolithic CVD SiC and nuclear grade SiC fiber – SiC matrix (SiC/SiC) composites were accurately determined, supported by the irradiation temperature determination for individual samples, following neutron irradiation within the lower transition swelling temperature regime. Slightly anisotropic swelling behaviors were found for the SiC/SiC samples and attributed primarily to the combined effects of the pre-existing microcracking, fiber architecture, and specimen dimension. A semi-empirical model of SiC swelling was calibrated and presented. Finally, implications of the refined model to selected swelling-related issues for SiC-based nuclar reactor components are discussed.
[en] This article describes the key design principles and application of a mini-bellows loaded irradiation creep frame technology developed for use in the high flux isotope reactor (HFIR). For this irradiation vehicle, the bellows, frame, sample, and temperature monitor are contained within a hydraulic or fixed “rabbit” capsule of a few inches in length. Of critical importance and key to this technology is the viability and stability of the metallic bellows under the elevated temperature irradiation environment. Conceptual design and supporting analysis have been performed for tension and compression specimens. Benchtop verification has substantiated the modeling regarding the ability of the bellows to produce sufficient stress to induce irradiation creep in subsize specimens. Discussion focuses on the possible stress ranges in specimens induced by the miniature gas-pressurized bellows and the limitations imposed by the size and structure of thin-walled bellows. A brief discussion of pre- and post-irradiation measurement of the integrity of load frames irradiated to 4.4 × 1025 n/m2 (E > 0.1 MeV) is presented. Following this protocol, the pre-irradiation loading to a sample is determined and post-irradiation loading inferred
[en] Highlights: • A new irradiation capsule for pressurized creep tube experiments in the High Flux Isotope Reactor has been developed. • This design uses a thin, crushable, corrugated foil to bond the pressurized tube to the capsule, eliminating the need for liquid immersion. • Four capsules have been constructed using this design, containing pressurized tubes made from the reduced ferritic/martensitic steel F82H, heat IEA. - Abstract: A novel capsule design has been developed for measurement of irradiation creep in pressurized tubes and is being used to irradiate reduced activation ferritic/martensitic F82H steel creep test specimens. These tests are being conducted in the flux trap of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The capsule design uses a tight-fitting corrugated aluminum foil placed in the center of a vanadium alloy holder to conduct heat from the centrally located test specimen. The foil acts as a compressible thermal interface between the pressurized tube and holder, maintaining a constant thermal resistance (and thus a constant tube temperature gradient) during irradiation, regardless of differential thermal expansion, creep, and swelling in the test specimen. Mechanical interference with creep deformation of the specimen tube is minimized by using a thin (0.05 mm) foil with sufficient room to crush. Finite element analysis of the contact pressure between the specimen and foil, combined with thermal creep in the foil, showed little interference with specimen stress conditions. Specimens were designed to experience hoop stresses of 380, 300, 150, and 0 MPa at a temperature of 300 °C while being irradiated to a dose of 3.7 dpa. Passive SiC thermometry is located within the pressurized tube and the holder material for confirmation of experiment irradiation target temperatures. This work discusses aspects of the capsule's fabrication and design, including thermal models of the capsule during irradiation.