Thermal performance sensitivity studies in support of material modeling for extended storage of used nuclear fuel

Abstract

SUMMARYThis report fulfills the M3 milestone M3FT-13PN0810025, "Perform Sensitivity Analysis Report", under Work Package FT-13PN081002.This report has been approved by all internal reviewers and is entered into the PNNL publication database (ERICA) as PNNL-22646.The U.S. Department of Energy Office of Nuclear Energy (DOE-NE), Office of Fuel Cycle Technology, established the Used Fuel Disposition Campaign (UFDC) to conduct research and development (R&D) to support storage, transportation, and disposal of used nuclear fuel and highlevel radioactive waste. Since nearly all potential degradation mechanisms are sensitive to temperature and in some cases, temperature history, the need for realistic, detailed temperatures and temperature distributions in the used nuclear fuel, storage canisters, and storage systems has been identified in an R&D gap analysis as one of several key cross-cutting needs.The work reported here is an investigation of the sensitivity of component temperatures in a specific storage system, including fuel cladding temperatures, in response to modeling assumptions that differ from design-basis, including age-related changes that could degrade the thermal behavior of the system. Preliminary evaluations of representative horizontal and vertical storage systems at design basis conditions provides general insight into the expected behavior of storage systems over extended periods of time. The sensitivity analyses were performed using the detailed computational fluid dynamics (CFD) model of a horizontal storage module developed for the inspections performed at the Calvert Cliffs Nuclear Power Station's Independent Spent Fuel Storage Installation (ISFSI) in June 2012.This storage module (designated HSM15) is a site-specific variant of the standard NUHOMS ® module, and contains a 24P dry shielded canister (DSC) loaded with twenty-four CE 14x14 spent fuel assemblies. The total decay heat load for the DSC in HSM15 was 10.58 kW at the time of loading (November 1996), after the fuel had spent approximately 12 years in wet storage. At the time of inspection (June 2012), after approximately16 years in dry storage, the total decay heat in the canister was calculated to be 7.58 kW. For the sensitivity analyses, the decay heat load for this fuel was projected to 300 years, and evaluations were performed for 6 kW, 4 kW, and 2 kW, corresponding to fuel approximately 50 years, 100 years, and 300 years old, respectively. The purpose of these sensitivity studies is to provide a realistic example of how changes in the physical properties or configuration of the storage system components can affect temperatures and temperature distributions. The magnitudes of these sensitivities can provide guidance for identifying appropriate modeling assumptions for thermal evaluations of extended storage of used nuclear fuel. Three specific areas of interest were identified for this study:• degradation of the canister backfill gas from pure helium to a mixture of air and helium, resulting from postulated leakage due to stress corros...

Sister Rod Destructive Test Results (FY19)

“…The flow through the fuel rod is modeled as Muskat's application of Poiseuille flow through a porous media (see Section 7.2). This pressure-driving force is related to the difference between the squares of the two volumes' pressures; the steady-state mass flow solution for two connected reservoirs at different pressures and constant temperatures through a flow impedance is (constant pressure, steady state conditions) [15,16,17]:…”

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Effects of Lower Drying-Storage Temperatures on the DBTT of High-Burnup PWR Cladding

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