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  <div class="section" id="xsproc-the-material-and-cross-section-processing-module-for-scale">
<span id="id1"></span><h1>XSPROC: The Material and Cross Section Processing Module for SCALE<a class="headerlink" href="#xsproc-the-material-and-cross-section-processing-module-for-scale" title="Permalink to this headline"></a></h1>
<p><em>M. L. Williams, L. M. Petrie, R. A. Lefebvre, K. T. Clarno, J. P.
Lefebvre, U. Merturyek, D. Wiarda, and B. T. Rearden</em></p>
<p>ABSTRACT</p>
<p>The modern material and cross section processing module of SCALE
(XSProc) was developed for the 6.2 release to prepare data for
continuous-energy and multigroup calculations. XSProc expands material
input from Standard Composition Library definitions into atom number
densities and, for multigroup calculations, performs cross section
resonance self-shielding, energy group collapse, and spatial
homogenization. XSProc implements capabilities for problem-dependent
temperature interpolation, calculation of Dancoff factors, resonance
self-shielding using Bondarenko factors with full-range intermediate
resonance treatment, as well as use of continuous energy resonance
self-shielding in the resolved resonance region. XSProc integrates and
enhances the capabilities previously implemented independently in
BONAMI, CENTRM, PMC, WORKER, ICE, and XSDRNPM, along with some
additional capabilities that were provided by MIPLIB and SCALELIB. The
use of the modern XSProc sequence instead of the legacy codes of
previous versions of SCALE generally results in the preparation of cross
sections in less time, with substantial speedups for more I/O bound
problems. Additionally, the memory requirements of XSProc are improved
by generating only the data needed for a particular calculation instead
of generating a general-purpose library that contains substantial
amounts of data that are not needed for a particular calculation.</p>
<p>ACKNOWLEDGMENTS</p>
<p>XSProc has evolved from the concept of a Material Information Processor
library (MIPLIB) that used alphanumeric material specifications, which
was initially proposed and developed by R. M. Westfall. J. R. Knight and
J. A. Bucholz expanded and refined MIPLIB in early SCALE releases.
Through SCALE 6.1, many enhancements were made by S. Goluoglu, D. F.
Hollenbach, N. F. Landers, J. A. Bucholz, C. F. Weber, and C. M. Hopper,
with L. M. Petrie taking the lead responsibility. With the SCALE
modernization initiative beginning in SCALE 6.2, MIPLIB is no longer
part of the XSProc analysis, but the original concepts and input
formatting were preserved in the new implementation. The authors wish to
thank Dan Ilas for helping convert the original MIPLIB documentation and
Sheila Walker for editing and formatting this document. Special thanks
to Don Mueller for his detailed review and checking of the document.</p>
<div class="section" id="introduction">
<span id="id2"></span><h2>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline"></a></h2>
<p>Self-shielding of multigroup cross sections is required in SCALE
sequences for criticality safety, reactor physics, radiation shielding,
and sensitivity analysis. In all previous versions of SCALE, resonance
self-shielding calculations were done by executing a series of
stand-alone executable codes, each dedicated to a specific aspect of the
self-shielding operations. Each sequence had its own unique internal
coding to launch the executable codes. Multigroup (MG) and
continuous-energy (CE) cross sections and other data were passed between
the individual executable codes by external I/O, which could require a
substantial amount of clock time. In the modern version of SCALE, all
self-shielding operations are consolidated into a single driver module
named XSProc, and the stand-alone executable codes have been transformed
into callable “computational modules” <span class="bibtex" id="id3">[rearden_modernization_2015]</span>. The
functions of XSProc are to (a) read input data, (b) generate in-memory
data structures (objects) containing problem-definition information
(compositions, cell geometries, computation options), as well as
self-shielding information (MG and CE cross sections and fluxes), and
(c) execute appropriate computational modules for the requested
self-shielding option. Calculated results produced by one module may be
stored in the internal data objects and passed to other modules through
application program interfaces (APIs). At the completion of XSProc the
self-shielded MG cross sections on the data objects can be passed along
to transport solvers for continued execution of the control sequence or
can be written to an external AMPX library file.</p>
<p>In the future, XSProc will be extended to parallel computations in which
self-shielding calculations are done simultaneously for multiple types
of unit cells. At the present time, however, XSProc is limited to serial
computations; but even in serial mode it typically requires less time
than older versions of SCALE to process shielded cross sections, and
significant speedups have been observed for heavily I/O bound problems.
Integrating the self-shielding capabilities into a single module has a
number of additional benefits as well, including maintainability,
extensibility, and the ability to easily replace an entire computational
module with a future implementation containing new features.
Additionally, the size of the problem-dependent MG library generated by
XSProc may be greatly reduced compared to previous versions of SCALE
because macroscopic cross sections are stored rather than a
general-purpose library of microscopic data.</p>
</div>
<div class="section" id="techniques">
<span id="id4"></span><h2>Techniques<a class="headerlink" href="#techniques" title="Permalink to this headline"></a></h2>
<p>XSProc integrates and enhances the capabilities previously implemented
independently in BONAMI, CENTRM, PMC, WORKER, ICE, and XSDRNPM, as well
as other capabilities formerly provided by MIPLIB and SCALELIB. It
provides capabilities for problem-dependent temperature interpolation of
both CE and MG nuclear data, calculation of Dancoff factors, and
resonance self-shielding of MG cross sections using several available
options. XSProc produces shielded microscopic data for each nuclide or
macroscopic data for each material. Additionally, a flux-weighting
spectrum can be applied to collapse cross sections to a coarser group
structure and/or to integrate over volumes for homogenized cross
sections. The flux-weighting spectrum can be input by the user or
calculated using one-dimensional (1-D) coupled neutron/gamma transport
model. These operations are performed by the sequences CSAS-MG, CSAS1,
CSASI, and T-XSEC described in <a class="reference internal" href="#id19"><span class="std std-ref">XSProc input data</span></a>.</p>
<div class="section" id="overview-of-xsproc-procedures">
<span id="id5"></span><h3>Overview of XSProc procedures<a class="headerlink" href="#overview-of-xsproc-procedures" title="Permalink to this headline"></a></h3>
<p>XSProc reads the COMPOSITION and CELL DATA blocks of the SCALE input,
which are described in the following sections. After reading the user
input data, XSProc loads the specified MG library to be self-shielded
and, depending on the selected self-shielding method, additional CE data
files for nuclides appearing in the problem specification. Finally
XSProc performs MG self-shielding calculations for all compositions by
calling APIs to computational modules such as BONAMI (<strong>BON</strong>darenko
<strong>AM</strong>PX <strong>I</strong>nterpolator), CRAWDAD (<strong>C</strong>ode to <strong>R</strong>ead
<strong>A</strong>nd <strong>W</strong>rite <strong>DA</strong>ta for <strong>D</strong>iscretized solution), CENTRM
(<strong>C</strong>ontinuous <strong>EN</strong>ergy <strong>TR</strong>ansport <strong>M</strong>odule), PMC
(<strong>P</strong>roduce <strong>M</strong>ultigroup <strong>C</strong>ross sections), CHOPS
(<strong>C</strong>ompute <strong>HO</strong>mogenized <strong>P</strong>ointwise <strong>S</strong>tuff), CAJUN
(<strong>C</strong>E <strong>AJ</strong>AX <strong>UN</strong>iter), WAX (<strong>W</strong>orking
<strong>A</strong>JA<strong>X</strong>), XSDRNPM (<strong>X</strong><strong>S</strong>ection <strong>D</strong>evelopment
for <strong>R</strong>eactor <strong>N</strong>ucleonics with <strong>P</strong>etrie
<strong>M</strong>odifications), and/or MIXMACRO to provide a problem-dependent
cross section library. Many computational modules have been modernized
compared to earlier executable codes distributed in previous versions of
SCALE.</p>
<p>Like earlier versions of SCALE, XSProc provides several options for
self-shielding an input MG library <a class="bibtex reference internal" href="Material%20Specification%20and%20Cross%20Section%20Processing%20Overview.html#williams-resonance-2011" id="id6">[Wil11]</a>. The first, based on the
Bondarenko method <a class="bibtex reference internal" href="Material%20Specification%20and%20Cross%20Section%20Processing%20Overview.html#ilich-bondarenko-group-1964" id="id7">[IlichB64]</a>, uses the computational module BONAMI. BONAMI is
always used to compute self-shielded cross sections for all energy
groups. If <em>parm=bonami</em> is specified, the shielded cross sections
provided by BONAMI are the final values output from XSProc. However the
Bondarenko method has several limitations, especially in the resolved
resonance range. Therefore XSProc provides another self-shielding
method, with several computation options, which often produces more
accurate MG data in the resolved resonance and thermal energy ranges. If
<em>parm=centrm</em> or <em>parm=2region</em> is specified on the sequence line,
XSProc calls APIs for the modules CRAWDAD, CENTRM, and PMC to compute CE
flux spectra for processing problem-specific, self-shielded cross
sections “on the fly <a class="bibtex reference internal" href="CENTRM.html#williams-computation-1995" id="id8">[WA95]</a>. CENTRM performs MG transport calculations in
the fast and lower energy ranges, coupled to pointwise (PW) transport
calculations that use CE cross sections in the resonance range. PMC uses
the PW flux spectra from CENTRM to compute MG values, which replace the
previous values obtained from BONAMI over the specified range of the CE
calculation. The original BONAMI shielded cross sections are retained
for all other groups.</p>
<p>The CENTRM/PMC approach is the default for criticality and lattice
physics calculations, while the BONAMI-only method is default for
radiation shielding calculations. The end results of an XSProc
calculation are self-shielded macroscopic and/or microscopic MG cross
sections stored in memory for subsequent transport calculations; or
alternatively a shielded MG AMPX library can be written to an external
file and saved for future use.</p>
</div>
<div class="section" id="standard-composition-material-processing">
<span id="id9"></span><h3>Standard composition material processing<a class="headerlink" href="#standard-composition-material-processing" title="Permalink to this headline"></a></h3>
<p>A primary function of the XSProc module is to expand user input in the
COMPOSITION block into nuclear number densities (nuclei/b-cm) for every
nuclide in each defined mixture. Mixtures can be specified through the
direct use of materials presented in the Standard Composition Library,
which includes individual nuclides, elements with natural abundances,
numerous compounds, alloys and mixtures found in engineering practice,
as well several variations of fissile solutions. Additionally, users may
define their own materials as atom percent or weight percent
combinations. Nuclear masses and theoretical densities are provided in
the Standard Composition Library, and methods are available to determine
equilibrium states for fissile solutions. Input options for composition
data are described in <a class="reference internal" href="#id20"><span class="std std-ref">Standard composition specification data</span></a> with several examples provided in
Appendix A.</p>
</div>
<div class="section" id="unit-cells-for-mg-resonance-self-shielding">
<span id="id10"></span><h3>Unit cells for MG resonance self-shielding<a class="headerlink" href="#unit-cells-for-mg-resonance-self-shielding" title="Permalink to this headline"></a></h3>
<p>XSProc utilizes a unit cell description to provide information for
resonance self-shielding calculations of the input mixtures. As many
unit cells as needed to describe the problem may be specified; however,
each mixture (other than 0 for a void mixture) can appear only in one
unit cell in the CELLDATA block. If a nuclide appears in more than one
mixture, multiple sets of self-shielded cross sections are calculated
for the nuclide—one for each mixture in each unit cell. Four types of
cells are available for self-shielding calculations: <strong>INFHOMMEDIUM</strong>,
<strong>LATTICECELL</strong>, <strong>MULTIREGION</strong>, and <strong>DOUBLEHET</strong>. The default
calculation type is CENTRM/PMC for CSAS (see <a class="reference internal" href="CSAS5.html#csas5"><span class="std std-ref">CSAS5:  Control Module For Enhanced Criticality Safety Analysis Sequences With KENO V.a</span></a>), TRITON, (see
<span class="xref std std-ref">3-0</span>) and TSUNAMI (see <span class="xref std std-ref">6-0</span>) sequences and BONAMI for MAVRIC.
All materials not specified in a unit cell are treated as infinite
homogeneous media and shielded with BONAMI only, unless the mixture
contains a fissionable nuclide, in which case an infinite medium
CENTRM/PMC model is used. Note that previous versions of SCALE used
infinite medium CENTRM/PMC calculations for all unassigned mixtures. The
default type of self-shielding calculation can be overridden, as
described in <a class="reference internal" href="#id19"><span class="std std-ref">XSProc input data</span></a>. The following is a brief description of
the types of unit cells that can be input in CELLDATA and the
computation procedures used.</p>
<div class="section" id="infhommedium-infinite-homogeneous-medium-treatment">
<span id="id11"></span><h4>INFHOMMEDIUM (infinite homogeneous medium) Treatment<a class="headerlink" href="#infhommedium-infinite-homogeneous-medium-treatment" title="Permalink to this headline"></a></h4>
<p>The <strong>INFHOMMEDIUM</strong> treatment is best suited for large masses of
materials where the size of each material is large compared with the
average mean-free path of the material or where the fraction of the
material that is a mean-free path from the surface of the material is
very small. When <strong>INFHOMMEDIUM</strong> cell is specified, the material in the
unit cell is treated as an infinite homogeneous lump. Systems composed
of small fuel lumps or resonance nuclides sandwiched between moderating
regions should not be treated as infinite homogeneous media. In these
cases a MULTIREGION or LATTICECELL geometry should be used.</p>
</div>
<div class="section" id="latticecell-treatment">
<span id="id12"></span><h4>LATTICECELL Treatment<a class="headerlink" href="#latticecell-treatment" title="Permalink to this headline"></a></h4>
<p>The <strong>LATTICECELL</strong> model is appropriate for arrays of resonance
absorber mixtures—with or without clad—arranged in a square or a
triangular pitch configuration within a moderator. Annular fuel (e.g.,
with an internal moderator in the center) can also be addressed. Input
data for the <strong>LATTICECELL</strong> treatment are described in <a class="reference internal" href="#id22"><span class="std std-ref">Unit cell specification for LATTICECELL problems</span></a>.
Self-shielded cross sections are generated for each material zone in a
unit cell of the lattice. If a nuclide appears in more than one zone,
self-shielded cross sections are produced for each zone where the
nuclide is present. Limitations of the <strong>LATTICECELL</strong> treatment are
listed below.</p>
<ol class="arabic simple">
<li><p>The cell description is limited to unit cells for arrays of
spherical, plate (slab), or cylindrical fuel bodies. In the case
of cylindrical pins in a square-pitch lattice, the default
(<em>parm=centrm</em>) self-shielding calculation uses the CENTRM method
of characteristics (MoC) option to represent the 2D rectangular
unit cell with reflected boundary conditions. By default,
self-shielding for all other arrays uses a CENTRM 1D S<sub>N</sub>
calculation for the unit cell (spherical and cylindrical
geometries use Wigner-Seitz cells). If <em>parm=bonami</em> is specified,
heterogeneous self-shielding effects are treated by equivalence
theory <a class="bibtex reference internal" href="Material%20Specification%20and%20Cross%20Section%20Processing%20Overview.html#williams-resonance-2011" id="id13">[Wil11]</a> The computation option <em>parm=2region</em>, described
in <a class="reference internal" href="#id18"><span class="std std-ref">XSProc data checking and resonance processing options</span></a>, can also be used for self-shielding lattice
cells.</p></li>
<li><p>Only predefined choices of cell configurations are available. The
available options are described in detail in <a class="reference internal" href="#id22"><span class="std std-ref">Unit cell specification for LATTICECELL problems</span></a>.</p></li>
<li><p>The basic treatment for <strong>LATTICECELL</strong> assumes an infinite, uniform
array of unit cells. This assumption is a good approximation for
interior fuel regions within a large, uniform array. The
approximation becomes less rigorous for fuel regions on the
periphery of the array or adjacent to a nonuniformity (e.g.,
control rod, water hole, etc.) in the lattice. For some cases it
may be desirable to address this issue by specifying a different
lattice cell for this type of fuel pin and using a modified
procedure to define an effective unit cell, as described below.</p></li>
</ol>
<p><em>***</em>* LATTICECELL treatment for nonuniform arrays*.</p>
<p>Nonuniform lattice effects may be treated in CENTRM calculation by
specifying the keyword <strong>DAN2PITCH=</strong><em>dancoff</em> in the optional CENTRM
DATA (see <a class="reference internal" href="#id26"><span class="std std-ref">Optional CENTRM DATA parameter data</span></a>). In this approach, the SCALE standalone code
MCDancoff must be run prior to the self-shielding calculation in order
to compute Dancoff factors for the fuel regions of interest in the
nonuniform lattice configuration. MCDancoff performs a simplified
one-group Monte Carlo calculation to compute Dancoff factors for complex
geometries (see <span class="xref std std-ref">7-8</span>). The Dancoff value for the fuel region of
interest is assigned to the DAN2PITCH keyword in the input for the
corresponding cell. Using an iterative procedure, CENTRM computes the
pitch of a uniform lattice that has the same Dancoff value as the
nonuniform lattice.</p>
</div>
<div class="section" id="multiregion-treatment">
<span id="id14"></span><h4>MULTIREGION Treatment<a class="headerlink" href="#multiregion-treatment" title="Permalink to this headline"></a></h4>
<p>The <strong>MULTIREGION</strong> treatment is appropriate for 1-D geometric regions
where the geometry effects may be important, but the limited number of
zones and boundary conditions in the <strong>LATTICECELL</strong> treatment are not
applicable. The <strong>MULTIREGION</strong> unit cell allows more flexibility in the
placement of the mixtures but requires all regions of the cell to have
the same geometric shape (i.e., slab, cylinder, sphere, buckled slab, or
buckled cylinder). Lattice arrangements can be approximated by
specifying a non-vacuum boundary condition on the outer boundary. See
<a class="reference internal" href="#id23"><span class="std std-ref">Unit cell specification for MULTIREGION cells</span></a> for more details. Limitations of the <strong>MULTIREGION</strong>
cell treatment are listed below.</p>
<ol class="arabic simple">
<li><p>A <strong>MULTIREGION</strong> cell is limited to a 1-D approximation of the
system being represented. An exact 1D model can be defined for the
following multizone geometries with vacuum boundary conditions:
spheres, infinitely long cylinders, and slabs; and for an infinite
array of slabs with reflected or periodic boundaries.</p></li>
<li><p>The shape of the outer boundary of the <strong>MULTIREGION</strong> cell is the
same as the shape of the inner regions. Cells with curved outer
surfaces cannot be stacked physically to create arrays; however,
arrays can be approximated by a Wigner-Sietz cell with a white
outer boundary condition, where the outer radius is defined to
preserve the area of the true rectangular or hexagonal unit cell.</p></li>
<li><p>Boundary conditions available in a <strong>MULTIREGION</strong> problem include
vacuum (eliminated at the boundary), reflected (reflected about
the normal to the surface at the point of impact), periodic
(a particle exiting the surface effectively enters an identical
cell having the same orientation and continues traveling in the
same direction), and white (isotropic return about the point of
impact). Reflected and periodic boundary conditions on a slab can
represent real physical situations but are not valid on a curved
outer surface. A single, non-interacting cell has a vacuum outer
boundary condition. If the cell outer boundary condition is not a
vacuum boundary, the unit cell approximates some type of array.</p></li>
<li><p>When using the CENTRM/PMC self-shielding method, the MULTIREGION cell
model must include fissionable material. This can be accomplished
by adding a trace amount of a fissionable material to one or more
mixtures, or by modeling a region of homogenized fuel and water,
or by adding a thin (e.g., 1e-6 cm-thick) layer containing at
least a trace of a fissionable nuclide on the periphery of the
problem.</p></li>
</ol>
</div>
<div class="section" id="doublehet-treatment">
<span id="id15"></span><h4>DOUBLEHET Treatment<a class="headerlink" href="#doublehet-treatment" title="Permalink to this headline"></a></h4>
<p><strong>DOUBLEHET</strong> cells use a specialized CENTRM/PMC calculational approach
to treat resonance self-shielding in “doubly heterogeneous” systems. The
fuel for these systems typically consists of small, heterogeneous,
spherical fuel particles (grains) embedded in a moderator matrix to form
the fuel compact. The fuel-grain/matrix compact constitutes the first
level of heterogeneity. Cylindrical(rod). spherical (pebble), or slab
fuel elements composed of the compact material are arranged in a
moderating medium to form a regular or irregular lattice, producing the
second level of heterogeneity. The fuel elements are also referred to as
“macro cells.” Advanced reactor fuel designs that use TRISO
(tri-material, isotopic) or fully ceramic microencapsulated (FCM) fuel
require the <strong>DOUBLEHET</strong> treatment to account for both levels of
heterogeneities in the self-shielding calculations. Simply ignoring the
double-heterogeneity by volume-weighting the fuel grains and matrix
material into a homogenized compact mixture can result in a large
reactivity bias.</p>
<p>In the <strong>DOUBLEHET</strong> cell input, keywords and the geometry description
for grains are similar to those of the <strong>MULTIREGION</strong> treatment, while
keywords and the geometry for the fuel element (macro-cell) are similar
to those of the <strong>LATTICECELL</strong> treatment. The following rules apply to
the <strong>DOUBLEHET</strong> cell treatment and must be followed. Violation of any
rules may cause a fatal error.</p>
<ol class="arabic simple">
<li><p>As many grain types as needed may be specified for each unique fuel
element. Note that grain type is different from the number of grains
of a certain type. For example, a fuel element that contains both
UO<sub>2</sub> and PuO<sub>2</sub> grains has two grain types. The same
fuel element may contain 10000 UO<sub>2</sub> grains and
5000 PuO<sub>2</sub> grains. In this case, the number of grains of type
UO<sub>2</sub> is 10000, and the number of grains of type PuO<sub>2</sub>
is 5000.</p></li>
<li><p>As many fuel elements as needed may be specified, each requiring its
own <strong>DOUBLEHET</strong> cell. This may be the case for systems with many
fuel elements at different fuel enrichments, burnable poisons, etc.
Each fuel element may have one or more grain types.</p></li>
<li><p>Since the grains are homogenized into a new mixture to be used in the
fuel element (macro-cell) cell calculation, a unique fuel mixture
number must be entered. XSProc creates a new material with the new
mixture number designated by the keyword f<em>uelmix=</em>, containing all
the nuclides that are homogenized. The user must assign the new
mixture number in the transport solver geometry (e.g., KENO) input
unless a cell-weighted mixture is created.</p></li>
<li><p>The type of lattice or array configuration for the fuel-element may
be spheres on a triangular pitch (<strong>SPHTRIANGP</strong>), spheres on a
square pitch (<strong>SPHSQUAREP</strong>), annular spheres on a triangular pitch
(<strong>ASPHTRIANGP)</strong>, annular spheres on a square pitch
(<strong>ASPHSQUAREP)</strong>, cylindrical rods on a triangular pitch
(<strong>TRIANGPITCH</strong>), cylindrical rods on a square pitch
(<strong>SQUAREPITCH</strong>),annular cylinderical rods on a triangular pitch
(<strong>ATRIANGPITCH)</strong>, annular cylindrical rods on a square pitch
(<strong>ASQUAREPITCH)</strong>, a symmetric slab (<strong>SYMMSLABCELL)</strong>, or an
asymmetric slab (<strong>ASYMSLABCELL)</strong>.</p></li>
<li><p>If there is only one grain type for a fuel element, the user must
enter either the pitch, the aggregate number of particles in the
element, or the volume fraction for the grains. The code needs the
pitch and will directly use it if entered. If pitch is not given,
then the volume fraction (if given) is used to calculate the pitch.
If neither the pitch nor the volume fraction is given, then the
number of particles is used to calculate the pitch and the volume
fraction. The user should only enter one of these items.</p></li>
</ol>
<blockquote>
<div><p>If the fuel matrix contains more than one grain type, all types are
homogenized into a single mixture for the compact. As for the one
grain type case, the pitch is needed for the spherical cell
calculations. However, the pitch by itself is not sufficient to
perform the homogenization. Since each grain’s volume is known (grain
dimensions must always be entered), entering the number of particles
for each grain type essentially provides the total volume of each
grain type and therefore enables the calculation of the volume
fraction and the pitch. Likewise, entering the volume fraction for
each grain type essentially provides the total volume of each grain
type and therefore enables the calculation of the number of particles
and the pitch. Therefore, one of these two quantities must be entered
for multiple grain types. In these cases, since pitch is not given,
the available matrix material is distributed around the grains of
each grain type proportional to the grain volume and is used to
calculate the corresponding pitch. Over-specification is allowed as
long as the values are not inconsistent to greater than 0.01%.</p>
</div></blockquote>
<ol class="arabic simple" start="6">
<li><p>For cylindrical rods and for slabs, fuel height must also be
specified. For slabs the slab width must also be specified.</p></li>
<li><p>The CENTRM calculation option must be S<sub>n</sub>.</p></li>
</ol>
</div>
</div>
<div class="section" id="cell-weighting-of-mg-cross-sections">
<span id="id16"></span><h3>Cell weighting of MG cross sections<a class="headerlink" href="#cell-weighting-of-mg-cross-sections" title="Permalink to this headline"></a></h3>
<p>Cell-weighted self-shielded cross sections are created when
<strong>CELLMIX</strong>= is specified in a <strong>LATTICECELL</strong> or <strong>MULTIREGION</strong> cell
input. In this case, after finishing the self-shielding calculations for
all mixtures in the cell, XSProc calls the computational module XSDRNPM,
which solves the 1-D MG transport equation to obtain k<sub></sub> and
space-dependent MG fluxes for the cell. The resultant fluxes are used to
compute MG flux disadvantage factors for processing cell-weighted
cross sections of all nuclides in the cell. When the cell-weighted
cross sections are used with <em>homogenized</em> number densities of the cell
nuclides, the reaction rates of the homogenized mixture preserve the
spatially averaged reactions rates of the heterogeneous configuration.
The user must input a new mixture ID to identify the homogenized mixture
associated with the cell-weighted cross sections. <strong>This homogenized
mixture should not be used in the heterogeneous geometry data for other
transport codes such as KENO, NEWT, etc.</strong> Instead, the cell-homogenized
mixture that is created should be used at the location of the original
cell. Also, cell weighted homogenized cross sections should not be used
in MG sensitivity data calculations performed using the TSUNAMI
sequences.</p>
</div>
</div>
<div class="section" id="xsproc-input-data-guide">
<span id="id17"></span><h2>XSPROC Input Data Guide<a class="headerlink" href="#xsproc-input-data-guide" title="Permalink to this headline"></a></h2>
<p>XSProc input data are entered in free form, allowing alphanumeric data,
floating-point data, and integer data to be entered in an unstructured
manner. Up to 252 characters per line are allowed. Data can usually
start or end in any column. Each data entry must be followed by one or
more blanks to terminate the data entry. For numeric data, either a
comma or a blank can be used to terminate each data entry. Integers may
be entered for floating values. For example, 10 will be interpreted as
10.0 if a floating point value is required. Imbedded blanks are not
allowed within a data entry unless an E precedes a single blank as in an
unsigned exponent in a floating-point number. For example, 1.0E 4 would
be correctly interpreted as 1.0 × 10<sup>4</sup>. A number with a negative
exponent must include an “E”. For example 1.0-4 cannot be used for
1.0E-4.</p>
<p>The word “END” is a special data item. An END may have a name or label
associated with it. The name or label associated with an END is
separated from the END by a single blank and is a maximum of
12 characters long. <em>At least two blanks or a new line MUST follow every
labeled and unlabeled END. WARNING: It is the user’s responsibility to
ensure compliance with this restriction. Failure to observe this
restriction can result in the use of incorrect or incomplete data
without the benefit of warning or error messages.</em></p>
<p>Multiple entries of the same data value can be achieved by specifying
the number of times the data value is to be entered, followed by either
R, *, or $, followed by the data value to be repeated. Imbedded blanks
are not allowed between the number of repeats and the repeat flag. For
example, 5R12, 5*12, 5$12, or 5R 12, etc., will enter five successive
12’s in the input data. Multiple zeros can be specified as nZ where n is
the number of zeroes to be entered.</p>
<div class="section" id="xsproc-data-checking-and-resonance-processing-options">
<span id="id18"></span><h3>XSProc data checking and resonance processing options<a class="headerlink" href="#xsproc-data-checking-and-resonance-processing-options" title="Permalink to this headline"></a></h3>
<p>To check the XSProc input data, run CSAS-MG and specify PARM=CHECK or
PARM=CHK after the sequence specification as shown below.</p>
<div class="highlight-scale notranslate"><div class="highlight"><pre><span></span><span class="nf">=CSAS-MG PARM=CHK</span>
</pre></div>
</div>
<p>In this case the actual XSProc cross section processing calculations are
not performed. The input data are checked, the problem description is
printed, appropriate error and warning messages are printed, and a table
of additional data is printed.</p>
<p>Resonance processing will automatically be performed by the default
method for the sequence selected. The default methods are CENTRM/PMC for
CSAS, TRITON, and TSUNAMI sequences and BONAMI for the MAVRIC sequences.
Alternatively, a resonance processing procedure may be chosen by
entering PARM=<em>option</em>, where <em>option</em> CENTRM selects the recommended
CENTRM/PMC transport method for each cell type, <em>option</em> 2REGION selects
the CENTRM/PMC two-region calculation, and <em>option</em> BONAMI applies full
range Bondarenko factors to all energy groups without utilizing
CENTRM/PMC. For example, to run CSAS1X sequence using only BONAMI for
self-shielding, rather than the default CENTRM/PMC method, enter the
computational sequence specification shown below.</p>
<div class="highlight-scale notranslate"><div class="highlight"><pre><span></span><span class="nf">=CSAS1X PARM=BONAMI</span>
</pre></div>
</div>
<p>Multiple PARM options are specified by enclosing parameters in
parenthesis, such as</p>
<div class="highlight-scale notranslate"><div class="highlight"><pre><span></span><span class="nf">=CSAS1X PARM=(CHK, BONAMI)</span>
</pre></div>
</div>
<p>XSProc resonance self-shielding options are summarized below.</p>
<p>PARM=BONAMI.</p>
<blockquote>
<div><p>This is the fastest MG processing method. It performs
resonance self-shielding for all energy groups using the Bondarenko
method. BONAMI computes the appropriate background cross section of a
given unit cell and then interpolates the corresponding shielding factor
from Bondarenko factors on the MG library. Dancoff factors needed to
evaluate the background cross section for lattices are computed
internally, but these can be overridden by input values in the MORE DATA
block. More details on this method are given in the BONAMI section of
the manual.</p>
</div></blockquote>
<p>PARM=CENTRM.</p>
<blockquote>
<div><p>This executes the CENTRM/PMC modules to process shielded MG
cross sections using CE flux spectra calculated with the recommended
type of CE transport solver for the designated type of cell. The
CENTRM-recommended CE transport solvers are (a) infinite homogeneous
medium calculation for INFHOMMEDIUM cells; (b) 2D MoC transport
calculation for a LATTICECELL consisting of cylindrical fuel pins in a
square lattice; and (c) 1-D discrete S<sub>n</sub> transport for all other
LATTICECELLs and for all MULTIREGION cells. The recommended type of
transport solver can be overridden for individual cells, as well as for
selected energy ranges, by using the CENTRM DATA block described in
<a class="reference internal" href="#id26"><span class="std std-ref">Optional CENTRM DATA parameter data</span></a>.</p>
</div></blockquote>
<p>PARM=2REGION.</p>
<blockquote>
<div><p>The CENTRM two-region (2R) option computes the PW flux using a
simplified collision probability method for an absorber (e.g., fuel)
region surrounded by an external moderator region which has an
asymptotic energy spectrum. To account for the heterogeneous effects of
a lattice, a correction known as the Dancoff factor is applied to the
escape probabilities in the 2R calculation (see the CENTRM chapter of
the SCALE manual). These Dancoff factors are calculated internally by
XSProc for a uniform array of mixtures in slab, spherical, or
cylindrical geometries. These mixture-dependent Dancoff factors can be
modified by user input using the DAN parameters contained in the MORE
DATA block, as defined in <a class="reference internal" href="#id25"><span class="std std-ref">Optional MORE DATA parameter data</span></a>.</p>
</div></blockquote>
<p><em>Note on CENTRM/PMC self-shielding options:</em></p>
<p>The energy range of the CENTRM flux calculation is subdivided into three
sections: fast, PW, and low energy. PMC only computes self-shielded
cross sections for groups within the PW range defined by parameters
<em>demax</em> and <em>demin</em>, which, respectively, define the upper and lower
energies of the CENTRM PW flux calculation. Problem-dependent cross
sections for groups in the fast and low energy ranges are obtained with
the more approximate BONAMI method. Default values for parameters
<em>demax</em> and <em>demin</em> are defined appropriately for self-shielding of
important resonance materials in thermal reactor systems. The PW
self-shielding range can be extended or decreased for individual cells
by modifying these parameters using CENTRM DATA.</p>
</div>
<div class="section" id="xsproc-input-data">
<span id="id19"></span><h3>XSProc input data<a class="headerlink" href="#xsproc-input-data" title="Permalink to this headline"></a></h3>
<p>The types of input data required for XSProc are given in <a class="reference internal" href="#tab7-1-1"><span class="std std-numref">Table 34</span></a>,
and individual entries are explained in the text following the table.
The title, cross section library name (either CE or MG), and standard
composition specification data (<strong>READ COMP</strong> input block) are required
for all sequences that use XSProc. The name of the cross section library
is used to determine if the transport solver is executed using CE or MG
data (e.g., CE or MG KENO calculations). The unit cell descriptions
(<strong>READ CELL</strong> input block) are only used for MG self-shielding
calculations. If the specified sequence executes in CE mode, the cell
data input can be omitted, or it will be skipped if present. If the cell
data information is omitted for MG calculations, all mixtures are
self-shielded using the infinite medium approximation.</p>
<p>There are seven standard SCALE sequences that run just XSProc, and
produce a MG cross section library or libraries.</p>
<p><strong>=XSPROC</strong> produces three libraries with an optional fourth library.</p>
<ul class="simple">
<li><p><strong>sysin.microLib</strong> is a self-shielded library of the individual
nuclides in the problem for use in a later transport calculation,</p></li>
<li><p><strong>sysin.macroLib</strong> is a self-shielded library of the mixture cross
sections in the problem for use in a later transport calculation,</p></li>
<li><p><strong>sysin.smallMicroLib</strong> is a self-shielded library of specific
reaction rate cross sections and the elastic and total inelastic
scattering transfer matrices for later use in calculating reaction
rates and sensitivity values, and</p></li>
<li><p><strong>sysin.xsdrnWeightedLib</strong> is an optional library produced if the
input specifies having <strong>XSDRN</strong> do a weighting calculation. This can
be a cell weighted and/or a group collapse calculation. The library
can be either individual nuclides or mixtures, depending on input.</p></li>
</ul>
<p><strong>=CSAS-MG</strong> produces an <strong>ft04f001</strong> library that is equivalent to the
<strong>sysin.microLib</strong>. With appropriate input it can also produce an
<strong>ft03f001</strong> which is equivalent to <strong>sysin.xsdrnWeightedLib</strong> above.</p>
<p><strong>=CSASI</strong> or <strong>=CSASIX</strong> produce an <strong>ft04f001</strong> library that is
equivalent to <strong>sysin.microLib</strong>, and an <strong>ft02f001</strong> library that is
equivalent to <strong>sysin.macroLib</strong>. CSASIX will run an <strong>XSDRN</strong> on the
first cell without any MOREDATA input. With appropriate input they both
can produce an <strong>ft03f001</strong> that is the equivalent of
<strong>sysin.xsdrnWeightedLib</strong>.</p>
<p><strong>=CSAS1</strong> or <strong>=CSAS1X</strong> produce an <strong>ft04f001</strong> library that is the
equivalent of <strong>sysin.microLib</strong>. Both sequences will run an <strong>XSDRN</strong>
on the first cell. With appropriate input, they both can produce an
<strong>ft03f001</strong> that is the equivalent of <strong>sysin.xsdrnWeightLib</strong>.</p>
<p><strong>=T-XSEC</strong> produces an <strong>ft04f001</strong> library that is equivalent to
<strong>sysin.macroLib</strong>. and an <strong>ft44f001</strong> library that is equivalent to
sysin.microLib.</p>
<p>The reactions (MT numbers) written to each library are listed in the
<code class="docutils literal notranslate"><span class="pre">SequenceNeutronMT.txt</span></code> file located in the etc directory installed with
SCALE.</p>
<span id="tab7-1-1"></span><table class="docutils align-center" id="id27">
<caption><span class="caption-number">Table 34 </span><span class="caption-text">Outline of XSProc input data</span><a class="headerlink" href="#id27" title="Permalink to this table"></a></caption>
<colgroup>
<col style="width: 25%" />
<col style="width: 25%" />
<col style="width: 25%" />
<col style="width: 25%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Data Position</p></th>
<th class="head"><p>Type of Data</p></th>
<th class="head"><p>Data Entry</p></th>
<th class="head"><p>Comments</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>1</p></td>
<td><p>Title</p></td>
<td><p>Enter title</p></td>
<td><p>Limit to 80
characters</p></td>
</tr>
<tr class="row-odd"><td><p>2</p></td>
<td><p>Cross section
library name</p></td>
<td></td>
<td><p>The currently
available
libraries are
listed in the
table <em>Standard
SCALE
cross-section
libraries</em> of
the XSLib
chapter.</p></td>
</tr>
<tr class="row-even"><td><p>3</p></td>
<td><p>Standard
composition</p>
<p>specification
data</p>
</td>
<td><p>Enter the
appropriate
data</p></td>
<td><div class="line-block">
<div class="line">Begin this
data block
with</div>
<div class="line"><strong>READ COMP</strong></div>
</div>
<div class="line-block">
<div class="line">and terminate
with</div>
<div class="line"><strong>END COMP</strong>.</div>
</div>
<p>See Section
<a class="reference internal" href="#id20"><span class="std std-ref">Standard composition specification data</span></a>.</p>
</td>
</tr>
<tr class="row-odd"><td><p>4</p></td>
<td><p>Unit cell(s)
description</p>
<p>for MG
calculations</p>
<p>only</p>
</td>
<td></td>
<td><p>Begin this data
block with
READ CELL (or
CELLDATA)</p></td>
</tr>
<tr class="row-even"><td></td>
<td><p>a. Type of self
shielding
calculation</p></td>
<td><p><strong>INFHOMMEDIUM</strong></p>
<p><strong>LATTICECELL</strong></p>
<p><strong>MULTIREGION</strong></p>
<p>DOUBLEHET</p>
</td>
<td><p>These are the
available
options.</p>
<p>See the
explanation in
Section
<a class="reference internal" href="#id19"><span class="std std-ref">XSProc input data</span></a>.</p>
</td>
</tr>
<tr class="row-odd"><td></td>
<td><p>b. Unit cell
geometry
specification</p></td>
<td><p>Enter the
appropriate
data</p></td>
<td><p>See
<a class="reference internal" href="#id21"><span class="std std-ref">Unit cell specification for infinite homogeneous problems</span></a>
<strong>INFHOMMEDIUM</strong></p>
<p>See Section
<a class="reference internal" href="#id22"><span class="std std-ref">Unit cell specification for LATTICECELL problems</span></a>
<strong>LATTICECELL</strong>
.</p>
<p>See Section
<a class="reference internal" href="#id23"><span class="std std-ref">Unit cell specification for MULTIREGION cells</span></a>
<strong>MULTIREGION</strong>
.</p>
<p>See Section
<a class="reference internal" href="#id24"><span class="std std-ref">Unit cell specification for doubly heterogeneous (DOUBLEHET) cells</span></a>
DOUBLEHET.</p>
</td>
</tr>
<tr class="row-even"><td></td>
<td><p>c. Optional
MORE parameter
data</p></td>
<td><p>Enter the
desired data</p></td>
<td><div class="line-block">
<div class="line">Begin this
data block
with</div>
<div class="line"><strong>MORE DATA</strong>
(or
<strong>MOREDATA</strong>)</div>
</div>
<div class="line-block">
<div class="line">and terminate
with</div>
<div class="line"><strong>END MORE</strong>
(or END
<strong>MOREDATA</strong>)</div>
</div>
<p>.</p>
<p>Use only if
MORE parameter
data are to be
entered;
otherwise, omit
these data
entirely. See
<a class="reference internal" href="#id25"><span class="std std-ref">Optional MORE DATA parameter data</span></a></p>
</td>
</tr>
<tr class="row-odd"><td></td>
<td><p>d. Optional
CENTRM
parameter data</p></td>
<td><p>Enter the
desired data</p></td>
<td><p>Begin this data
block with</p>
<p><strong>CENTRM DATA</strong>
(or
<strong>CENTRMDATA</strong>)</p>
<p>and terminate
with</p>
<p><strong>END CENTRM</strong>
(or END
<strong>CENTRMDATA</strong>)
.</p>
<p>Use only if
CENTRM
parameter data
are to be
entered;
otherwise, omit
these data
entirely.</p>
</td>
</tr>
<tr class="row-even"><td></td>
<td><p>e. End of unit
cell data</p></td>
<td></td>
<td><p>Terminate with
END CELL (or
END CELLDATA)</p></td>
</tr>
<tr class="row-odd"><td><p>Repeat
positions 4a–4d
as needed to
specify all
unit cells.
Position 4 data
are applicable
to the MG
calculations
only.</p></td>
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<ol class="arabic simple">
<li><p>TITLE. An 80-character maximum title is required. The title is the
first 80 characters of the XSPROC data.</p></li>
<li><p>CROSS SECTION LIBRARY NAME. This item specifies the cross section
library that is to be used in the calculation. See Table <em>Standard
SCALE cross-section libraries</em> in the XSLIB chapter of the SCALE
manual for a discussion of the available libraries.</p></li>
<li><p>The keywords <strong>READ COMP</strong> followed by the standard compositions
specifications. These data are used to define mixtures used in the
problem. See <a class="reference internal" href="#id20"><span class="std std-ref">Standard composition specification data</span></a> and <a class="reference internal" href="#tab7-1-2"><span class="std std-numref">Table 35</span></a> for a description of