Abstract
Writing an input deck for the Group-organized cross-section Input
Program (GIP) can be quite a challenge, especially for those who do not
ordinarily work in discrete ordinates. Material compositions must be
specified for each Pn component individually and only in terms of atomic
densities, i.e. atoms/(b cm). In order to make the input of material
information more logical and closer to physical reality, GipGui was
written. This interactive utility allows the user to specify materials
in a variety of ways, including molecular formula and weight fractions.
The separate Legendre components are handled automatically, not as
separate nuclides, so the user can focus on true materials. At present
GipGui operates as an interface to standard GIP input files, but stops
short of executing GIP, since the former activity presents the hardest
challenge to many users of codes in the Discrete Ordinates of Oak Ridge
(DOORS) package. GipGui is designed to be backwards compatible with
minor restrictions, hence it reads and manipulates existing GIP input
files, as well as allows the user to start from scratch.
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What Scott Adams has to say about engineers who design their own
interfaces.
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1. INTRODUCTION
GIP[1] is the standard cross-section manipulation code used in preparing
cross-section data for the neutral particle transport codes comprising
the Discrete Ordinates of Oak Ridge System (DOORS[2]) package, e.g. ANISN,
DORT, and TORT[3]. All distributed versions of DOORS include the GIP code
in addition to other peripheral codes that work in conjunction with the
primary transport codes to address a broader class of problems
encountered in applications[4]. The programming environment of the mid
1960's in which GIP was developed had tight constraints on the amount of
memory that can be dedicated to execution of a given code. Hence much of
the peculiarities of computer codes that were born in that environment
appear unjustifiable in the present computational environment
characterized by large physical and virtual memory size, and high
processor speed. As an example, the treatment of the Pn components of
the scattering cross section for a specific nuclide as a set of distinct
nuclides was an innovative solution designed to reduce memory
requirement without introducing significant changes to the logic and
structure of other related codes. As a result of such non-intuitive
programming practices, the primitive nature of the programming languages
in which many early neutronics codes were written, and poor user
interfacing, GIP is viewed by many in the user community as a powerful
and necessary but extremely difficult computational tool. GipGui is
designed to remove this burden from the users by implementing an
interactive intuitive interface between the user and standard GIP input
files that is backwards compatible with a few restrictions. Hopefully,
by using GipGui, the chances of introducing errors into the mixed cross
sections will be reduced.
GipGui is written in Java in an effort to be platform independent. This
is an alpha version that was written to see if there was a desire in the
discrete ordinates community for such a tool. At the present time,
GipGui only prepares the input deck, it will not run GIP. Future
additions could include: ability to handle special instructions, such as
those multiplying a cross section by a constant or operations dealing
with just one Legendre component; ability to read an actual library
instead of a library index file; ability to run GIP directly from the
GipGui. There are also a number of data checks that GipGui does not
handle that can be added to help the user create the actual GIP input
file.
2. DETAILED DESCRIPTION
2.1. Coding Language
GipGui is written in Java 1.3 and distributed as a single JAR file (Java
ARchive, similar to a unix tar file but executable).
2.2. Nature of Problem Solved
GipGui can create from scratch or modify existing GIP input deck text
files. This interface creates the group-by-group instructions from the
user's physical descriptions of materials.
2.3. Method of Solution
2.3.1. Library index file
GIP input decks refer to the materials that are listed in a library
file, often a very large file. GipGui needs to know only about the
structure of such a library, it does not need to access the actual
cross-section data in the library. So, GipGui uses a library index file,
which the user will have to create for each real library he uses.
The first line in the index file specifies the number of energy groups,
the number of upscatter groups, the number of downscatter groups, the
number of activation groups, total upscatter (0-no, 1-yes) and finally
the total number of records in the library. Text comments may follow.
line 1 format: int int int int int int text_comments
Then, for each library material, specify in one line the record number
of the P0 component, the highest order component, a useful name, e.g.
nuclide identifier, and any comments enclosed in quotes.
format: int int name "text_comments"
For example, an index file might look like this:
69 0 0 68 1 612 taken from last year's project
1 7 al27 "v94.10 standard wgt e61132"
9 5 am241 "v94.10 standard wgt e63954"
15 5 am242 "v91.94 standard wgt e62954"
601 5 y89 "v91.94 standard wgt e61392"
607 5 zr "v91.94 standard wgt e62400"
Only materials that the user wishes to mix need to be listed, although
line one must include the actual total number of materials in the full
library whether they are used or not. Extra spaces don't hurt - they can
be used for easier human readability. The index file can be created
using any text editor or through the editing tools of GipGui.
2.3.2. GipGui Layout
The main screen of GipGui, shown in Figure 1, is laid out in blocks that
the user will typically use in a top-to-bottom, left-to-right manner.
Following is a brief description of the input blocks of the GipGui main
screen:
Problem Title - The problem title is a part of the standard GIP input
deck.
GIP Problem Parameters - The number of energy groups, number of
activation groups, number of upscatter groups and the number of
downscatter groups can be specified by the user. If a library index file
is being used, these four values for the GIP input deck will be forced
to match those listed in the library index file. Once an index file has
been loaded or isotopes have been manually entered, these numbers are no
longer editable. The scattering order is editable until an isotope data
is manually entered.
Cross-Section Library Index File - If one is not specified at the start
of GipGui, the user may load or create a new index file. Once one is
loaded, the user may edit it. Note that this will not change the
library, since the library index file is independent of the actual
library.
Manually Entered Isotope Data - This allows the user to add, edit and
delete the isotopes entered into GIP manually (not through a library) as
is often done in simple testing configurations. The list shows the
currently defined isotopes. To edit or delete an isotope, click on it
and then select the edit or delete button. A new isotope can be added at
any time.
GIP Output Parameters - Standard part of GIP input, these describe what
you want GIP to produce.
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Figure 1. The main screen for GipGui.
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Mixtures of Isotopes (Manually Entered/Library) - This is the heart of
GIP, the specification of mixtures of library materials and the manually
entered isotope data. Typically, the library and manually entered
isotope data are microscopic cross sections (in units of barns) and they
are usually mixed to generate macroscopic cross sections (in units of
per cm). Macroscopic cross sections can also be combined to form other
macroscopic cross sections.
The list shows the currently defined mixtures. To edit or delete a
mixture, click on it and then select the edit or delete button. A
mixture can be added at any time. When adding a new mixture, there are
several different ways to specify the combination of the individual
ingredients. These ways are:
- by atomic densities - in atoms/(b cm)
- by atom fractions - with total in atoms/(b cm)
- by atomic densities - in atoms/cm3
- by atom fractions - with total in atoms/cm3
- by mass densities - in g/cm3
- by mass fractions - with total in g/cm3
- by molecular formula - in atoms per molecule
- unitless - user supplies multiplier
For some of these methods, data for the mixture must be entered before
the ingredients can be specified. As the user enters the required data,
the factors that GIP needs for mixing materials together are computed.
These are shown in a pop-up "Edit Mixture" window. Mixture ingredients
may be edited in different units than they were input into the mixture,
so long as any additional required data is provided by the user.
Mixtures of Isotopes and Other Mixtures - These mixtures behave just
like the mixtures above, except that the list of possible ingredients is
not limited to the library and isotopes, but includes all of the
mixtures of isotopes and the mixtures of mixtures. These can be either
microscopic or macroscopic cross sections. The real reason to split the
mixtures into two groups is simply to aid the user and try to prevent
unit mismatches.
As the user enters new materials (mixtures, isotopes, library materials)
or changes the names of old materials, GipGui will try to provide the
mass data if it recognizes the new name. The name is searched for
element names, symbols and mass numbers. If an appropriate isotope is
found, that mass is used, if not, the elemental data is used. For
example, the names "U", "uranium231", or "U235" will set the mass to be
238.029, 231.0362892 or 235.0439231 g/mol. Using a name such as "orange
metal" will give a mass of 15.9994 g/mol (the first letter is "o", as in
oxygen). The user may of course override these guessed masses with his
own values.
Special Instructions (Future Work) - This is not functional at this
time. In the future, this will hold all of the special instructions that
GIP is capable of handling, such as multiplying a mixture by a constant,
or doing something to one Pn component of a material, instead of all the
components of that material.
Element/Isotope Data - This is provided as a service to the user. Click
on any element and its isotopic data will appear in the lower scroll
pane. When entering mixture ingredients, the user invariably needs this
sort of data.
Useful Constants - This is also provided to the user as a simple convenience.
2.4. Restrictions or Limitations
GipGui is the initial step in developing a modern cross-section
manipulation and maintenance software to replace GIP. The primary
purpose of GipGui is to provide a modern interface that is compatible
with existing GIP input files. As such GipGui is not designed to handle
some unnecessary, and seldom used, capabilities of GIP. Following is a
list of presently known limitations, and users are encouraged to
communicate to the author any additional limitations they discover:
- "=gip" and "=end" not permitted:
Limitation: The JDOS instructions
"=gip" at the beginning, and "=end" at the end, of a GIP input file
cause GipGui to crash.
Solution: Remove these lines before opening the
input file with GipGui.
- Stacked cases:
Limitation: JDOS allows the user to stack GIP input
data for multiple runs in the same input file, changing the unit number
of the binary output file between runs. GipGui processes only the first
case in a sequence of runs of this sort.
Solution: Separate the input
for multiple cases into separate input files prior to opening them with
GipGui.
- Only / permitted as comment character:
Limitation: The additional comment characters ' and " cause GipGui to hang;
only the comment character / is recognized by GipGui.
Solution: Replace ' and " with /; this can be done easily via the unix line editor,
ed, commands:
1,$ s/'/\//g
1,$ s/"/\//g
- Empty lines read as zeros:
Limitation: Lines with no alphanumeric characters in the middle of an
array are interpreted as zeros by GipGui.
Solution: Remove clear lines
within an array input, or to preserve readability, comment out with "/".
- 0 entry in 10$ array not permitted:
Limitation: This is an antiquated contrivance used in one of the sample input files
distributed with TORT to process kerma factors (for which there are no higher
Pn moments). It is neither necessary nor intuitive, hence it is not allowed by GipGui.
Solution: Examine the GIP input file prior to opening it with GipGui and modify
the intent of zeros in the 10$ array with equivalent standard instructions.
2.5. Typical Running Time
For all cases tested, the runtime on various platforms was within the
fraction of a minute time scale. Large amounts of user-input isotope
data for many-group problems could take several minutes to load.
2.6. Computer Hardware Requirements
GipGui has been tested on Windows systems and Linux systems. Since it is
distributed as a single JAR file, GipGui should be able to be run
anywhere that Java can be installed.
2.7. Computer Software Requirements
Java 1.3 or higher is required. Java can be downloaded, free of charge,
from the Sun Microsystems, Inc. web page,
http://java.sun.com/
2.8. Contents of Code Package
The code itself is contained in a single JAR file. Also available are
example GIP input decks and example library index files. Help is
provided via an *.html file, which is embedded in the JAR file.
3. SUMMARY
GipGui is still in its very earliest development. Users of GIP are
encouraged to contact the authors for a copy of GipGui to test for their
own use. Feedback is greatly appreciated - the whole reason for the
development of GipGui is to help the discrete ordinates community. With
support and input from the users, GipGui will be improved.
ACKNOWLEDGMENTS
Oak Ridge National Laboratory is managed and operated by UT-Battelle,
LLC for the U.S. Department of Energy under Contract No.
DE-AC05-00OR22725.
REFERENCES
- J. O. Johnson, Ed., "A User's Manual for MASH 1.0 - A Monte Carlo
Adjoint Shielding Code System", ORNL/TM-11778, Oak Ridge National
Laboratory, (March 1992).
- W. A. Rhoades and R. L. Childs, RSICC Computer Code Collection
CCC-650, "DOORS-3.2, One-, Two- and Three-Dimensional Discrete Ordinates
Neutron/Photon Transport Code System" (July 1998).
- W. A. Rhoades and D. B. Simpson, "The TORT Three-Dimensional
Discrete Ordinates Neutron/Photon Transport Code" ORNL/TM-13221 (1997).
- Y. Y. Azmy, "The Three-Dimensional, Discrete Ordinates Neutral
Particle Transport Code TORT: An Overview," OECD/NEA Meeting on 3D
Deterministic Radiation Transport Computer Programs, Features,
Applications, and Perspectives, December 2-3, 1996, Paris, France, p. 17
(1997).
This document was last updated 20030204
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