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SummaryThis report fulfills the M3 milestone M3FT-12PN0810041, "Report on Realistic Temperature Profiles", under Work Package FT-12PN081004.As part of the Used Fuel Disposition Campaign of the Department of Energy (DOE), visual inspections and temperature measurements were performed on two storage modules in the Calvert Cliffs Nuclear Power Station's Independent Spent Fuel Storage Installation (ISFSI). The inspection procedure included surface temperature measurements on one end of the DSC within the storage module. The data obtained in the inspections at Calvert Cliffs provide an opportunity to develop structural and thermal models that can yield realistic temperature predictions for actual storage systems, in contrast to conservative and bounding design basis calculations.Detailed models of the concrete storage modules to be examined were developed using STAR-CCM+ (version 7.02; CD-Adapco, 2012). The immediate purpose of this modeling effort is to obtain temperature predictions in actual storage conditions for the module, DSC, and DSC contents, including preliminary estimates of fuel cladding temperatures for the SNF. The long-term goal of this work is to obtain realistic evaluations of thermal performance of actual SNF storage systems over extended periods, which will require developing a detailed COBRA-SFS (Michener, et al., 1987) model of the DSC internals, in addition to the large system models. The approach used in this study omits many of the conservatisms and bounding assumptions normally used in design-basis and safety-basis calculations for spent fuel storage systems. The results of this study cannot be used in licensing basis evaluations of the Calvert Cliffs ISFSI, or any other spent fuel storage facility.The storage modules used for this study are HSM-1 and HSM-15 in the Calvert Cliffs Nuclear Power Station's ISFSI, each containing a 24P DSC loaded with 24 CE 14x14 spent fuel assemblies. The total decay heat load for the DSC in HSM-15 was 10.8 kW at the time of loading, and was calculated to be 7.6 kW as of June 2012. The total decay heat load for the DSC in HSM-1 was calculated to be 4.1 kW as of June 2012. The base case for thermal evaluation of the 24P DSC in HSM-15 assumed an ambient temperature of 58°F (14°C). This value was determined using historical climatology data from a National Oceanic and Atmospheric Administration (NOAA) database, and verified with annual ambient temperature data from monitoring stations at the Calvert Cliffs ISFSI. Bounding sensitivity studies on the effect of ambient air temperature were performed for two cases; a 'summer case' at 77°F based on average temperatures in July, and a 'winter case' at 35°F, based on average temperatures in January. Figure On June 27 th and 28 th , 2012, visual inspections, surface sampling, and temperature measurements were performed on HSM-1 and HSM-15 at the Calvert Cliffs Nuclear Power Station ISFSI. Due to physical constraints on the accessible regions of the DSC and considerations of worker safety, reliable temperature measuremen...

In 2007, a severe transportation accident occurred near Oakland, California, at the interchange known as the “MacArthur Maze.” The accident involved a double tanker truck of gasoline overturning and bursting into flames. The subsequent fire reduced the strength of the supporting steel structure of an overhead interstate roadway causing the collapse of portions of that overpass onto the lower roadway in less than 20 minutes. The US Nuclear Regulatory Commission has analyzed what might have happened had a spent nuclear fuel transportation package been involved in this accident, to determine if there are any potential regulatory implications of this accident to the safe transport of spent nuclear fuel in the United States. This paper provides a summary of this effort, presents preliminary results and conclusions, and discusses future work related to the NRC’s analysis of the consequences of this type of severe accident.

Hydrologic exchange is a critical mechanism that shapes hydrological and biogeochemical processes along a river corridor. Because of limitations in field accessibility, computational demand, and complexities of geomorphology and subsurface geology, full three‐dimensional modelling studies to quantify hydrologic exchange fluxes (HEFs) have been limited mostly to local‐scale applications. At reach scales, although surface flow conditions and subsurface physical properties are well‐known factors that modulate hydrologic exchanges, quantitative measures that can describe the effects of these factors on the strength and direction of such exchanges do not exist. To address this issue, we developed a one‐way coupled surface and subsurface water flow model using the commercial computational fluid dynamics (CFD) software STAR‐CCM+ and applied it to simulate HEFs in a 7‐km long reach along the main stem of the Columbia River in the United States. The model was validated against flow velocity measurements from an acoustic Doppler current profiler in the river, vertical HEFs estimated from a set of temperature profilers installed across the riverbed, and simulations from a reactive transport model. The validated model then was employed to systematically investigate how HEFs could be influenced by surface water fluid dynamics, subsurface structures, and hydrogeological properties. Our results suggest that reach‐scale HEFs are dominated primarily by the thickness of the riverbed alluvium layer, and then by the alluvium permeability, the depth of the underlying impermeable layer, and the pressure boundary condition. Our results also elucidate the scale dependence of HEFs on fluid dynamics that can be captured only by three‐dimensional CFD models. That is, while the net HEFs over the entire 7‐km domain are not significantly influenced by surface water dynamics pressure, the dynamic pressure induced by fluid dynamics can lead to more than 15% in net HEFs for a river section of a few hundred metres.

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Regulatory agencies are considering alternative approaches to assessing inhalation toxicity that utilizes in vitro studies with human cells and in silico modeling in lieu of additional animal studies. In support of this goal, computational fluid-particle dynamics (CFPD) models were developed to estimate site-specific deposition of inhaled aerosols containing the fungicide, chlorothalonil, in the rat and human for comparisons to prior rat inhalation studies and new human in vitro studies. Under bioassay conditions, the deposition was predicted to be greatest at the front of the rat nose followed by the anterior transitional epithelium and larynx corresponding to regions most sensitive to local contact irritation and cytotoxicity. For humans, simulations of aerosol deposition covering potential occupational or residential exposures (1—50 µm diameter) were conducted using nasal and oral breathing. Aerosols in the 1-5 µm range readily penetrated the deep region of the human lung following both oral and nasal breathing. Under actual use conditions (aerosol formulations >10 µm), the majority of deposited doses were in the upper conducting airways. Beyond the nose or mouth, the greatest deposition in the pharynx, larynx, trachea, and bronchi was predicted for aerosols in the 10–20 µm size range. Only small amounts of aerosols >20 µm penetrated past the pharyngeal region. Using the ICRP clearance model, local retained tissue dose metrics including maximal concentrations (Cmaxs) and areas under the curve (AUCs) were calculated for each airway region following repeated occupational exposures. These results are directly comparable with benchmark doses from in vitro toxicity studies in human cells leading to estimated human equivalent concentrations (HEC) that reduce the reliance on animals for risk assessments.

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