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Research Papers: Operations, Applications & Components

Thermal Performance Analysis of Geologic High-Level Radioactive Waste Packages

[+] Author and Article Information
Si Y. Lee

Steve J. Hensel

 Savannah River National Laboratory, Savannah River Site, Aiken, SC 29808steve.hensel@srnl.doe.gov

Chris De Bock

ONDAF/NIRASBelgium

J. Pressure Vessel Technol 133(6), 061601 (Oct 13, 2011) (13 pages) doi:10.1115/1.4003823 History: Received September 17, 2010; Accepted February 18, 2011; Published October 13, 2011; Online October 13, 2011

The engineering design of disposal of the high level waste (HLW) packages in a geologic repository requires a thermal analysis to forecast the temperature history of the packages. Calculated temperatures are used to demonstrate compliance with criteria for waste acceptance into the geologic disposal gallery system and as input to assess the transient thermal characteristics of the vitrified HLW Package. The objective of the work was to evaluate the thermal performance of the supercontainer containing the vitrified HLW in a nonbackfilled and unventilated underground disposal gallery. In order to achieve the objective, transient computational models for a geologic vitrified HLW package were developed by using a computational fluid dynamics method, and calculations for the HLW disposal gallery of the current Belgian geological repository reference design were performed. An initial simplified two-dimensional model was used to conduct some parametric sensitivity studies to better understand the geologic system’s thermal response. The effect of heat decay, number of codisposed supercontainers, domain size, humidity, thermal conductivity, and thermal emissivity were studied. A more accurate three-dimensional model was also developed by considering the conduction–convection cooling mechanism coupled with radiation, and the effect of the number of supercontainers was studied in more detail, as well as a bounding case with zero heat flux at both ends. The modeling methodology and results of the sensitivity studies will be presented.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Modeling domain and geometry (total length of the two canisters = 2771 mm)

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Figure 2

Transient volumetric heat sources as function of geologic storage time used for the present

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Figure 9

Temperature distributions at 4.5 storage years along the horizontal gallery tunnel

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Figure 10

Overall air flow patterns due to natural convection for the back-filled region of the gallery tunnel crossing the middle of the horizontal supercontainer after about 5 years’ storage

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Figure 11

Air velocity profiles along the line A-A′ for the top air space of the gallery tunnel at about 5 storage years

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Figure 12

Temperature contours at about 5 storage years along the central vertical plane of the gallery tunnel for case-1 (numbers in the color code are in °C)

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Figure 13

Temperature distributions along the lines, A-A′, B-B′, and C-C′, for the supercontainer components for the gallery tunnel containing three supercontainers along the horizontal gallery drift tunnel after about 4 years (case-2)

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Figure 14

Comparison of temperature distributions along the top overpack surface for three supercontainers stored inside the gallery tunnel after about 4 years

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Figure 15

Comparison of supercontainer surface temperature distributions for different numbers of supercontainer storages with 16 m empty air space on LHS end and insulation boundary at RHS end

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Figure 16

Peak overpack surface temperatures for different numbers of supercontainer storages with 16 m empty air space on LHS end and insulation boundary at RHS end at various storage times

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Figure 3

Initial temperature distributions along the vertical centerline of the supercontainer with 50 m soil domain and 40 °C supercontainer surface temperature, 20 °C initial air temperature, and 15.7 °C initial soil temperature

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Figure 4

Transient maximum surface temperatures for overpack and supercontainer between two different models with baseline decay heat source

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Figure 5

Transient maximum surface temperatures for overpack and supercontainer between two different models with homogenized decay heat source

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Figure 6

Transient maximum temperatures for overpack and supercontainer surfaces for Case-1

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Figure 7

Temperature distributions for the Case-1 model for the vertical cross-sectional plane crossing the middle of the horizontal supercontainer after 4.5 years’ storage

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Figure 8

Temperature distributions for supercontainer surfaces for the Case-1 (3 supercontainers) at t = 4.5 years

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