Irradiation Performance

The activities of the Irradiation Performance Section (IPS) are aimed at determining and assessing normal-operation and accident behavior of neutron-irradiated material throughout the life cycle of the materials. The conditions of interest are normal in-reactor operation, design-basis accidents, intermediate storage in pools and dry casks, and ultimate internment in a repository. Fuel and cladding materials (fission reactors) and tritium-breeder and structural materials (fusion reactors) are exposed to intense neutron and gamma radiation fields, high temperatures and heat fluxes, and corrosive environments. Pre-test characterization, testing and post-test characterization are used, along with fundamental materials science and modeling, to determine the response of these nuclear materials to their radiation, temperature, and chemical environments. The expertise in ceramic and metal fuels, tritium-breeder ceramics, cladding and structural materials remains within IPS. However, the focus of the research has shifted with a major change in facilities available for testing. Prior to 2006, characterization and testing of irradiated fuel, cladding and fueled-cladding were conducted in the Alpha-Gamma Hot Cell Facility (AGHCF), while mechanical properties of defueled cladding and structural materials were measured in the Irradiated Materials Laboratory (IML). In early 2006, the AGHCF was closed to programmatic work. The current emphasis is on continuing the research on cladding and structural materials in refurbished glove boxes and the beta-gamma hot cells in the IML.

The facilities currently available for IPS research include glove boxes and IML hot cells for work with irradiated materials and general laboratory space for characterization and testing of as-fabricated and pre-hydrided materials. The glove boxes in radiological laboratory DL-114 have been refurbished to enable: pre- and post-test hydrogen-, oxygen-, and nitrogen-content determination, optical microscopy sample preparation and imaging, sample sectioning, tungsten-inert-gas (TIG) welding, and laser welding of irradiated cladding alloys. One glove box contains a computer-controlled furnace for heating and cooling of sealed-and-pressurized rodlets to simulate the thermal-mechanical conditions of spent nuclear fuel during drying, transfer and storage operations. The two hot cells dedicated to sample preparation and testing include: (a) an electro-discharge machine for precise cutting of gauge sections for mechanical properties testing of irradiated cladding and structural materials and (b) the LOCA (loss-of-coolant-accident) Integral and Oxidation Apparatus for determining the response of high-burnup cladding alloys to high-temperature steam oxidation and water quench. Mechanical properties of as-irradiated cladding, LOCA-oxidized cladding, and dry-cask-stored cladding are measured in a servohydraulic Instron machine enclosed in a glove box. Baseline data for as-fabricated and pre-hydrided materials are generated with similar equipment in non-radiological laboratories.

Spent nuclear fuel cladding following slow cooling from 400°C and peak hoop stresses of (a) 140 MPa and (b) 80-MPa. L_R is radial hydride length and h_m is cladding alloy thickness. Radial hydrides precipitated at high hoop stress are long and embrittle the cladding at transportation temperatures ≤180°C. Radial hydrides precipitated at low stress are short and benign even at room temperature.

Current research efforts are focused on the characterization and testing of light-water-reactor cladding following high-burnup operation, reactor discharge, pool storage, and cask drying-transfer-storage to determine potential degradation mechanisms (e.g., precipitation of radial hydrides during slow cooling under pressure-induced stresses) that may challenge cladding integrity during post-storage transport and post-transport handling. In addition to IPS research activities, the IML is used to assist Argonne User Facilities, such as the Advanced Photon Source (APS) and the Intermediate Voltage Electron Microscopy (IVEM-Tandem) Facility, as well as university students and professors who use these facilities to characterize irradiated materials. The irradiated materials are either within the IML inventory or they come from test reactors used to irradiate the materials. These activities include receipt of shipping casks, unloading, measurement of dose rates and contamination levels, mechanical and chemical sample cleaning to reduce dose rates and contamination levles, and transfer/transport to the user facility. To date, universities who have used the IML for these purposes include Penn State University, the University of Illinois, and Purdue University.

Last Modified: Tue, October 3, 2017 5:00 PM