Daily Thermal Predictions of the AGR-1 Experiment with Gas Gaps Varying with Time Page: 4 of 13
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Proceedings of ICAPP '12
Chicago, USA, June 24-28, 2012
ST Holder ,_
sule Spacer _
Fig 4. Three-dimensional cutaway rendering of
single AGR-1 capsule.
JI.A. Finite Element Mesh
Fig 5 shows the finite element mesh with a cutaway
view of the entire model. A Cartesian coordinate system is
appropriate for this model because of the three fuel stacks
making it non-symmetric. Approximately 350,000 eight-
noded hexahedral brick elements were entirely used in all
the models. A set of conduction-convection elements was
used to model the flow of the water. All other elements
were modeled solely for diffusion heat transfer. Several
mesh convergence studies have been performed on the
mesh. Identical agreement for this mesh and a mesh with
twice as many elements in each direction was performed.
The graphite holder and fuel compacts were modeled as
0.1016 m lengths, but most of the heat comes from the fuel
compacts and not from the outer components. The water is
the ultimate heat sink for each capsule. The graphite holder
with its two end-cap spacers and ring were modeled for the
inner part of the model. A radiation boundary sink
temperature of (204.4 C) is placed on the top and bottom
of each graphite end cap. This value came from previous
models discussed in Reference  for typical operating
I.B. Compact Thermal Conductivity
The fuel compact thermal conductivity was taken from
correlations presented from Gontard in Reference 
which gives correlations for conductivity, taking into
account temperature, temperature of heat treatment,
neutron fluence, and TRISO-coated particle packing
compacts -. _ '
graphite spacers ,
Fig 5. Sideways cutaway view of mesh with colored
In this work, the convention used to quantify neutron
damage to a material is fast fluence E >0.18 MeV, yet in
the work by Gontard , the unit used was the dido nickel
equivalent (DNE). In order to convert from the DNE
convention to the fast fluence >0.18 MeV, the following
conversion was used:
_>18MeV = 1..52 DNE (1)
where IF is neutron fluence in either the >0.18 MeV
unit or DNE. The correlations in the report by Gontard 
were further adjusted to account for differences in fuel
compact density. The correlations were developed for a
fuel compact matrix density of 1.75 g/cm3, whereas the
compact matrix used in AGR-1 had a density of
approximately 1.3 g/cm3. The thermal conductivities were
scaled according to the ratio of densities (0.74) in order to
correct for this difference.
Fig 6 shows a three-dimensional plot of the fuel
compact thermal conductivity varying with fluence and
temperature. For fluences greater than 1.0 x 1025
neutrons/n2 (E > 0.18 MeV), the conductivity increases as
fluence increases for higher temperatures, while the
opposite occurs at lower temperatures because of the
annealing of radiation-induced defects in the material with
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Hawkes, Grant; Sterbentz, James; Maki, John & Pham, Binh. Daily Thermal Predictions of the AGR-1 Experiment with Gas Gaps Varying with Time, article, June 1, 2012; Idaho Falls, Idaho. (digital.library.unt.edu/ark:/67531/metadc832963/m1/4/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.