Dry Storage and Transportation of High Burnup Spent Nuclear Fuel – Final Report (NUREG-2224)

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Publication Information

Manuscript Completed: November 2020
Date Published: November 2020

Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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The purpose of this report is to expand the technical basis in support of the U.S. Nuclear Regulatory Commission's (NRC's) guidance on adequate fuel conditions as it pertains to hydride reorientation in high burnup (HBU) spent nuclear fuel (SNF) cladding. This guidance defines adequate fuel conditions, including peak cladding temperatures during short-term loading operations to prevent or mitigate degradation of the cladding. Time-dependent changes on the cladding properties of HBU SNF are primarily driven by the fuel's temperature, rod internal pressure (and corresponding pressure-induced cladding hoop stresses), and the environment during dry storage or transport operations. Historically, safety review guidance has addressed the potential for these changes to compromise the analyzed fuel configuration in dry storage systems and transportation packages.

Hydride reorientation is a process in which the orientation of hydrides precipitated in HBU SNF cladding during reactor operation changes from the circumferential-axial to the radial-axial direction. Research results over the last decade have shown that hydride reorientation can still occur at temperatures and stresses lower than those assumed in the current staff review guidance. Therefore, the NRC has since sponsored additional research to better understand whether hydride reorientation could affect the mechanical behavior of HBU SNF cladding and compromise the fuel configuration analyzed in dry storage systems and transportation packages.

This report provides an engineering assessment of the results of research on the mechanical performance of HBU SNF following hydride reorientation. Based on the conclusions of that assessment, the report then presents example approaches for licensing and certification of HBU SNF for dry storage (under Title 10 of the Code of Federal Regulations (10 CFR) Part 72, "Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High-Level Radioactive Waste, and Reactor-Related Greater Than Class C Waste") and transportation (under 10 CFR Part 71, "Packaging and Transportation of Radioactive Material").

The NRC expects these example licensing and certification approaches, when followed by applicants, to minimize or eliminate the need for requests for additional information during the staff's safety review of applications for dry storage and transportation of HBU SNF. Further, the NRC expects that future revisions of the standard review plans for dry storage systems and transportation packages will reference the licensing and certification approaches delineated in this NUREG.

The information in this report is not intended for use in applications for wet storage facilities or monitored retrievable storage installations licensed under 10 CFR Part 72.

Nothing contained in this report is to be construed as having the force or effect of regulations. Comments regarding errors or omissions, as well as suggestions for improvement of this NUREG, should be sent to the Director, Division of Spent Fuel Management, U.S. Nuclear Regulatory Commission, Washington, DC, 20555-0001.

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