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SCALE 6.2.3 Update

To request the SCALE 6.2.3 update, please contact

April 2018

The SCALE 6.2.3 update is available for SCALE 6.2 users as of April 2018, providing enhanced features and performance in the areas detailed below. This update is provided as a download and is recommended for all SCALE 6.2.0, 6.2.1, and 6.2.2 users. The 6.2.3 update includes all previous updates and can be applied directly on any SCALE 6.2 release.

Polaris Enhancements

SCALE 6.2.3 introduces several enhancements to the Polaris lattice physics code.

  • Users will notice the ~2× speedup in run time for depletion calculations.
  • A new restart feature reuses the geometry data structures and flux solution from previous calculations.
  • Polaris has a new detector edit capability in SCALE 6.2.3. Input examples of the detector card for a PWR 17 × 17 lattice model and for a BWR 7 × 7 lattice model are shown in Figure 2, and an example of detector response output is shown in Figure 3. The key inputs and their descriptions are given here.
    • Detector material (Lines 24, 25). In this input, a trace amount of 235U is used to define material DET.1.
    • Detector geometry (Line 26). The detector geometry is provided through the Polaris pin card. In this input, the detector geometry is a simple zone of coolant with pin ID "D."
    • Detector definition (Line 27). In this input, the detector "d_235" is defined as pin D inserted into pin IT. The detector response is the neutron fission rate "E(n, FIS)." The detector cross section is from DET.1 (i.e., 235U), and the detector flux is the COOL.2 flux inside the detector geometry.
    • Opt FG input (Line 48). The detector option on the opt FG card designates the detector edit to be included on the t16 file. 


Self-shielding method selection logic: SCALE 6.2.3 includes improved consistency for self-shielding logic across all sequences and now enables the user to use the BONAMI-only methodology for faster calculations or in cases where the CENTRM methodology is not suitable. In SCALE 6.2.3, the logic has been streamlined as follows:

  • 1. CENTRM for double-heterogeneous cells,
  • 2. BONAMI for infinite homogeneous (inf. hom.) cells without fissionable nuclides,
  • 3. For inf. hom. cells with fissionable nuclides, choose
    • method specified by user in parm data (CENTRM, BONAMI, XSLEVEL, 2REGION) or
    • sequence defaults
      • CENTRM for t-newt, t-xsdrn, t-depl-1d, t-depl, csas1x, csas5, csas6, t keno, t-depl-3d, tsunami-1d, tsunami-3d
      • BONAMI for Mavric, XSProc sequence  

Numerical stability in CENTRM MoC solver: An issue was identified with the default option for lattice cell self-shielding in cases with very small macroscopic cross section < 10-7 cm-1. During the
calculations, CENTRM produced nonphysical fluxes, shown as not a number, or NaN. Analyses of typical LWR configurations are not expected to be affected. The issue was resolved in SCALE 6.2.3 by introducing a more robust way to handle very small macroscopic cross sections, with negligible impact on memory and runtime.

Coupled neutron/gamma: An issue was discovered in CENTRM in which enabling upscattering in a coupled neutron/gamma problem produced erroneous results. This was recognized due to no gammas leaving the problem domain. As a temporary stop-gap for SCALE 6.2.3, upscattering will not be allowed in coupled neutron/gamma calculations.

Minor miscellaneous issues resolved in XSPROC 
In the output of XSProc with lattice cell self-shielding, the printout was corrected where a radius quantity was incorrectly labeled as a diameter.

The XSDRN Balance table file (ft76.btf) was missing its lambda value. The lambda value is now included in the balance table file.

The XSPROC section of the manual has been updated to include a description of the double-heterogeneous self-shielding treatment (e.g., for TRISO particle models) for SLAB geometry. Previously, only a description of the capability for SPHERE geometry was present.

There has been some confusion over the filenames used by the various SCALE sequences/modules that write a cross section library to disk. In SCALE 6.2.3, the various filenames used by each sequence/module have been clearly documented in the SCALE manual. For SCALE 6.3, a more consistent naming scheme will be implemented, perhaps with the additional capability for the user to choose the name.


KENO-V.a boundary condition: An issue was identified in SCALE 6.1–6.2.2. An unexpected behavior can occur when a user generates an input that is inconsistent with the documentation and training materials and the code does not detect the input error before executing. SCALE behaves as intended if users generate models consistent with the documentation and training materials. Details and corrective actions are presented
in the section below entitled "SCALE 6.1–6.2.2 KENO-V.a boundary condition issue.”

Reaction cross sections: In continuous energy (CE) KENO, the method for calculating average reaction cross sections, which are of particular importance in CE TRITON depletion calculations, has been modified
to increase robustness. Previously, multigroup reaction cross sections were calculated at each active generation and were averaged over all active generations to arrive at the best estimate. For SCALE 6.2.3, the methodology has changed so that the multigroup reaction rates and fluxes (instead of reaction cross sections) are accumulated over active generations and after all active generations are complete, the reaction cross sections are calculated as the reaction rate divided by flux. An additional positive effect of the change is that the options for tallying reaction cross sections, cxm=2 (multigroup xs) and cxm=4 (1-group xs), generally show better agreement.

Reaction rate output: An output processing issue was discovered in the KENO reaction rate output: absorption (MT=27) and capture (MT=101) cross sections were not being updated when constituent cross sections for scattering (MT=2), fission (MT=18), inelastic scattering to the first excited state (MT=51), and n,gamma (MT=102) cross sections are sampled from probability tables in the unresolved resonance region (URR). This does not impact the transport calculation or depletion calculations under t5-depl or t6-depl that use the constituent cross sections directly. This issue was discovered by a user attempting to calculate keff from reaction rate output and match the result to the output eigenvalue. Analysis using the reaction rate output where the URR range is important should be repeated with SCALE 6.2.3.

Minor miscellaneous issues resolved in KENO
The output for the Shannon entropy convergence test has been updated in SCALE 6.2.3 to emphasize where active generations are used.

The nuclide identifiers for metastables and bound nuclides were not correctly displayed in the KENO output. These isotope edits are now correct.

Filenames for reaction rates have been tallied. Instead of ${BASENAME}.keno_micro_rr.* in SCALE 6.2.2, KENO in SCALE 6.2.3 writes reaction rate tallies in ${BASENAME}.keno_rr.*.

The Doppler broadening of CE cross sections to user-specified temperatures in KENO now allows for four options for the DBX parameter:

  • 0 = No problem-dependent or on-the-fly Doppler broadening
  • 1 = Perform problem-dependent Doppler Broadening for 1D cross sections only
  • 2 = Perform problem-dependent Doppler Broadening for both 1D and 2D (thermal scattering data) cross sections
  • 3 = Broaden 2D cross sections normally, and broaden 1D cross sections using a less robust but faster interpolation method.

DBX=3 was previously only supported as an option in Monaco.

Occasionally, the Doppler broadening of very small cross sections can result in very small negative values for a few data points. The effect of these values on criticality and reaction rates is undetectable, but these very small negative values could cause CE TSUNAMI sensitivity calculations to fail. In SCALE 6.2.3 these values are set to zero.


Undefined mixtures: For cases that have undefined mixtures referenced in the geometry, NEWT calculations assumed that any mixture that did not include any data in the cross section library was a void material with a cross section of zero. This issue has been fixed in SCALE 6.2.3, and additional checks and error messages have been added to verify that every mixture referenced in the geometry is defined in the composition block. This issue affects all uses of NEWT, including the t-newt and t-depl sequences.


Neutron emission calculations: An issue was found in ORIGEN in which a tolerance for including a nuclide in the emission calculation did not include the initial isotopics. Thus, any nuclide that fell below the threshold over the first timestep would not be included in the neutron emission calculation for the entire case. For common timestep sizes on the order of days, the main effect was that the delayed neutron emitters, which have effective time ranges of much less than a day, are bypassed, and no delayed neutron information is shown. The issue was fixed in SCALE 6.2.3 by including the initial isotopics in the time-averaging to determine the active nuclides for an emission calculation. A workaround for SCALE 6.2.0, 6.2.1, and 6.2.2 is to add a very small, initial timestep (on the order of milliseconds).

Volume input: ORIGEN volume input is only used when the user specifies the isotopic input by number density, and the volume is needed to convert the number density to ORIGEN's internal mole units. However, unlike other SCALE sequences, number density input is not commonly used in ORIGEN. Volume input was not being correctly handled in SCALE 6.2.2. Any calculations using the number density input option should be rerun using SCALE 6.2.3.

Elemental input: A minor change was made regarding how ORIGEN handles elemental input. It is now flagged as an error which specifies any element for which the natural abundances sum to zero (e.g., Tc) according to the data on the specified ORIGEN library. Note that the current ORIGEN library format only allows abundances for light nuclides (hydrogen to lead), so it does not include natural uranium.

ARPLIB utility module: This module, which is used to manipulate the number of burnup-dependent data sets on an ORIGEN library, was not properly processing libraries in the SCALE 6.2 format. In SCALE 6.2.3, ARPLIB properly reads the SCALE 6.2 library format (and SCALE 6.1 format) and has been redesigned to allow the user to easily create an arbitrary library from cross sections using data from a number of other available libraries. Note that this utility module is rarely used for thinning or combining existing libraries. The module does not intervene in any ORIGEN calculation or SCALE sequences involving ORIGEN.


Significant Polaris enhancements are discussed in this newsletter under “Polaris Enhancements.” A new preview capability is available for basic detector modeling and gamma transport. This is fully described in the appendix of the Polaris manual in SCALE 6.2.3. As with earlier previews, =polaris_6.3 must be used as the sequence name. Users may experience a runtime reduction of 10–50% due to optimization of some internal initialization routines.

Minor issues resolved in Polaris
Mismatches between user-specified symmetry and actual problem symmetry are now better recognized. Defining compositions with names that are also element symbols (e.g., Zr or F) is no longer allowed. Rare convergence issues occurring with CMFD and buckling calculations are now fixed. In the Polaris nodal data file (T16 or X16 file): energy release per fission parameters now properly include energy released from capture, and few-group flux is normalized as per source neutron instead of per source neutron per unit volume.


Perturbed decay data: The uncertainty in the decay energy release (aka Q-value) for primary alpha emitters was found to be at least 50% larger than the actual value due to an issue in the sampling code that is used to generate the 1,000 perturbed decay data files. The code error has been fixed. The updated perturbed decay data files are not available as part of the SCALE 6.2.3 release, but they will be made available as an additional download. This only affects Sampler uncertainty calculations with perturb_decay=”yes” (the default is “no”). Moreover, it only affects the decay heat uncertainty prediction; it does not affect the decay heat prediction itself. Validation of calculated decay heat against measured spent fuel decay heat has shown good agreement, typically within 2%, between predicted and measured values. SCALE developers are committed to making uncertainty calculations a simple, routine part of nuclear engineering analysis. Additional tests will be applied to the current data set, along with new uncertainty data from ENDF/B-VIII.

Minor issues resolved in Sampler
The output to additional auxiliary files (recommended for post-processing of the sampled results with a tool external to SCALE) only contained a single significant digit instead of the desired five significant digits. If the
input only used a single sample, then Sampler would show standard deviations of 0.0 (or for some outputs, NaN) instead of the more appropriate infinity.


Calculations using thorium: TRITON did not correctly include thorium (atomic number 90) in the definition of initial heavy metal (IHM) for the purpose of setting specific power levels (units of MW/MTIHM) and reporting burnup (MWd/MTIHM). The error has been corrected in SCALE 6.2.3, and a verification problem using 232Th was added to the regression suite. The error made it impossible to deplete a thorium-only mixture, and for a mixture that included thorium, the input power was misinterpreted, and burnup was misreported. Any depletion calculations for thorium in SCALE 6.2.0–6.2.2 are incorrect and should be rerun with 6.2.3.

Keep block: In TRITON, keeping the ORIGEN output (origen keyword found in the keep block) would lead to extremely large transition coefficient tables in the TRITON output file, and cases with many burnup points could have output file sizes in gigabytes. In SCALE 6.2.3, requesting TRITON to keep origen will only enable output of detailed depletion number density tables. To recover the previous output, which may be useful in small problems to understand specific depletion pathways, the user must indicate to keep both ORIGEN and COUPLE output in the keep block.

Self-shielding and material swap: In TRITON (MG) within SCALE 6.2, the interaction between self-shielding and the material swap (and control rod branch) has changed. In previous versions, the mixture swap occurred before self-shielding. This required users to take the swap into account when creating the celldata block. In SCALE 6.2 and later versions, self-shielding in the celldata block is based only on the defined mixtures. This difference only affects calculations in which latticecell or multiregion self-shielding is used with swaps or control rod branches. It does not affect the default inf. hom. In SCALE 6.2.3, the user is warned when these conditions are present.


Autocomplete: SCALE 6.2.3’s Fulcrum now has the ability to validate and autocomplete the MAVRIC input.

Visualization: Lines in OPUS plot files now display in different colors instead of only blue. Covariance data color bar limits and axis fonts can now be changed.

Input Editor: Input validation is now faster by a factor of two, is fully case insensitive, accounts for all possible SCALE sequences (including utility modules), and is no longer disrupted by uncommented text preceding
a sequence. New error messages are emitted if a user attempts to create a new file without the proper write permissions. If a user attempts to view a geometry for an input that has no geometry, then appropriate error messages are displayed. The cursor retains its original position when a text file is reloaded instead of moving to the top of the file.

Other Minor Miscellaneous Issues Resolved in SCALE 6.2.3

The legacy addnux value of -2, which was disabled in TRITON in SCALE 6.2.2, has been included again in SCALE 6.2.3.

In SCALE 6.2.3, various updates have been implemented in the STARBUCS burnup credit analysis sequence for consistency with updates in KENO and ARP.

ORIGAMI now allows the simulation of an initial decay interval, for example, to simulate some initial decay time before the first irradiation. This is accomplished by entering a power level of zero for the first cycle, which would previously cause the calculation to fail. Additionally, the format MCNP source output (enabled with mcnp=yes) has been updated for improved compatibility with MCNP.

In TSURFER, a minor issue was corrected in which the printout of cross section adjustment information (print_adjustments) did not work.

An issue was discovered with the SCALE composition block’s atom type input in which the atom fractions that were entered were being treated as weight fractions. This issue has been resolved in SCALE 6.2.3. Note that this only affects atom composition inputs (e.g., “atom 1 19.0 2 92235 0.1 92238 0.9 end”), which is a rarely used form.

SCALE 6.2.2 Update

May 30, 2017

The SCALE 6.2.2 update is available for SCALE 6.2 and SCALE 6.2.1 to provide enhanced performance and resolve issues in the areas detailed below. This update is provided as a download and is recommended for all SCALE 6.2 and 6.2.1 users. New licenses for SCALE 6.2.1 will include the SCALE 6.2.2 update. The SCALE 6.2.2 incorporates all updates made since the SCALE 6.2 release so that users can proceed directly to the SCALE 6.2.2 update even if the SCALE 6.2.1 has not been applied. 

General Enhancements Available in Many SCALE Sequences

Oxygen-18 cross section treatment: SCALE 6.2.2 includes an update to address a deficiency in ENDF/B-VII.0 and VII.1 where no cross-section data are available for O-18 even through the natural abundance of oxygen includes 0.2% O-18. When using the SCALE Standard Composition Library with natural abundances, materials with missing cross sections are omitted from the material data before the calculation proceeds by setting the number density to zero. As such, a small amount of mass is removed when natural abundance oxygen is used in a model. To resolve this issue, a new feature was implemented for all sequences in SCALE 6.2.2 in that a zero-valued cross section is added for O-18 so that material masses are maintained. Criticality and shielding calculations will generate the same results when using either a zero number density or a zero cross section. Depletion calculations may demonstrate an insignificant variation due to the use of specific powers that use the system mass which will vary slightly with this update. However, all material tables will demonstrate that mass is preserved and warning messages only not that a zero cross section was used because the material is not available on the specified library.

Doppler broadening of ZrH thermal moderators: Thermal moderator Doppler broadening in continuous-energy Monte Carlo calculations was improved to address an issue that caused a large bias in results for  systems containing ZrH. Any temperature corrected continuous-energy calculations for systems with ZrH should be rerun with the new SCALE version.


With SCALE 6.2.2 several new features were implemented for Polaris to model boiling water reactor (BWR) geometries. Moreover, the ability to specify time-dependent state properties and the ability to specify one or more depletion histories were added and improvements to existing input cards were implemented.

To maximize backwards compatibility for input files developed with SCALE 6.2 and SCALE 6.2.1, the new and modified input cards are not available by default with SCALE 6.2.2. The new and modified input cards are activated if the input file begins with =polaris_6.3 rather than =polaris. The suffix “_6.3” is an indicator to the Polaris input processor to use the SCALE 6.3 input format.  For the future release of SCALE 6.3, the original input cards supported in the SCALE 6.2 input format will be available if the input file begins with =polaris_6.2.

The new input cards to model BWR geometries include:

  • cross – define the interior water cross geometry of SVEA assembly designs;
  • dxmap (or dymap) – define displacement maps that indicate that translation of the pin center in the x- (or y-) direction;
  • control <BLADE> - define the control blade geometry;
  • mesh – define advanced spatial meshing options for different materials; and
  • option <GEOM> – define geometry tolerances, advance meshing options, and plotting options.

The modified input cards to model BWR geometries include:

  • pin – define circular and square-based geometry zones, as well as arbitrarily sized pins, e.g. size=1.5 water rod in some 9x9 BWR lattice designs; and
  • box – define channel box geometry with arbitrary number of zones and cutout regions.

The new input cards for time-dependent modeling include:

  • history – define one or more operating histories in the input file; and
  • bui (or ti) – define restart cumulative burnup (or time) values.

The modified input cards for time-dependent modeling include:

  • state – define one or more time-independent or time-dependent state properties;
  • bu (or t) – define cumulative burnup (or time) values; and
  • dbu (or dt) – define incremental burnup (or time) values.

Example input files are included in SCALE 6.2.2 in the ${SCALE}/regression/input directory:

  • polaris.6.3.atrium9x9.inp and polaris.6.3.atrium10x10.inp – prototypic ATRIUM models;
  • polaris.6.3.blade1.inp and polaris.6.3.blade2.inp – control <BLADE> examples;
  • polaris.6.3.ge7x7.inp through polaris.6.3.ge10x10.inp – prototypic GE models;
  • polaris.6.3.svea100.inp and polaris.6.3.svea64.inp – prototypic SVEA models; and polarisHistory.inp: history example.


T-DEPL ASSIGN capability: The TRITON T-DEPL ASSIGN feature is enabled for problems with BRANCH, TIMETABLE and SWAP definitions.

TRITON depletion with CE-KENO: A discrepancy was introduced in SCALE 6.2.1 for continuous-energy TRITON/KENO calculations that included both a TIMETABLE input block and carbon in a depleted mixture can lead to erroneous isotopic predictions. This issue was not present in SCALE 6.2. Any SCALE 6.2.1 continuous-energy TRITON/KENO calculations that include a TIMETABLE and carbon in a depleted mixture should be rerun with SCALE 6.2.2.

TRITON depletion with MG-KENO: TRITON/KENO multi-group depletion with DOUBLEHET multigroup processing was enhanced to complete all requested burnup steps where previous calculations would sometime terminate prematurely.

“nubar” component in TRITON-generated libraries for ORIGEN: ORIGEN has a special, rarely-used, "k-infinity" output option. This "k-infinity" is calculated as "nubar*sigma_f/sigma_a", where "nubar" is the average number of neutrons per fission, "sigma_f" is the fission cross section, and "sigma_a" is the absorption cross section; the data used for this calculation are taken from the ORIGEN library file produced by TRITON (f33 file). TRITON in SCALE 6.2 and 6.2.1 is not correctly setting the "nubar" component in this file, and all ORIGEN reactor libraries distributed with SCALE (in ${DATA}/arplibs directory) are affected by this. This issue has been addressed in the SCALE 6.2.2 update. Note, this does not affect the accuracy of depletion calculations with TRITON or ORIGEN in SCALE 6.2, only the special "k-infinity" output, if requested in ORIGEN. 

TRITON edits: Printed information for TRITON branch case calculations has been enhanced to provide more complete state information.


CE TSUNAMI-3D calculations using the Iterated Fission Probability (IFP) and Generalized Perturbation Theory (GPT) methods now use variance reduction technique of Monte Carlo particle splitting, which was disabled for these specific sensitivity methods in SCALE 6.2 and 6.2.1. The results for IFP and GPT calculations with SCALE 6.2.2 will vary from previous results within the stochastic uncertainty of the calculation, but the runtimes will be improved by 10-40%.

CE TSUNAMI-3D CLUTCH method (i.e. CET=1) was updated to correct a rare issue. For only one case, it was found that the importance function portion of the CLUTCH calculation becomes corrupted, creating unreasonable sensitivity coefficients with very large uncertainties. CLUTCH calculations that may be corrupted by this identified bug would run to completion, but would not match direct perturbation confirmations. Any previous CLUTCH calculations that display these aspects should be rerun with SCALE 6.2.2.

SAMS was updated to correctly process a user-specified covariance data file. Previous calculations that used the COVERX= input to specify a non-default covariance file should be checked to confirm that the desired covariance file was used.

Minor miscellaneous issues resolved:

Corrected an issue where .plt files were sometimes not returned to the output directory when running many simultaneous calculations.

USLSTATS was updated for improved stability where some cases would fail to run to completion.

ORIGAMI was updated to correct an issue where MCNP formatted material cards sometimes contained incorrect number densities. Previous calculations with ORIGAMI to generate MCNP material cards should be checked to confirm the number densities.

Sampler was enhanced for improved stability on Windows.

Minor issues with legacy ORIGEN FIDO formatted input were corrected.

Several minor enhancements in output information were incorporated.

Several minor enhancements in the Fulcrum user interface were incorporated.

Minor discrepancies in the user documentation were also corrected. 

SCALE 6.2.1 Update

August 23, 2016

The SCALE 6.2.1 update is available for SCALE 6.2 to provide enhanced performance and resolve issues in the areas detailed below. This update is recommended for all SCALE 6.2 users.

Please contact your distribution center (RSICC, NEA Data Bank, or RIST) to obtain this update.

Significant Updates: 

The TRITON T-DEPL features ASSIGN and SWAP were updated for SCALE 6.2.1 to correct issues that could affect the results of SCALE 6.2 calculations. SCALE 6.2 T-DEPL calculations that use ASSIGN and/or SWAP should be reanalyzed with SCALE 6.2.1. Please see the list of Known Issues with SCALE 6.2 for more details.

Details of all updates:


A restriction that limited CRAWDAD to treating only up to 100 temperatures has been removed.

A memory defect was resolved that could cause a 'glibc' crash for some cases.


Fulcrum was enhanced with several new features for SCALE 6.2.1.

Fulcrum now supports text block column operations. By using the ALT+Left mouse button drag, a block of text is selected and can be deleted, pasted, edited, etc.

Fulcrum no longer incorporates the file name into the file specific action items (save, save as, etc). When conducting a Save as, the name is pre populated with the current file name.

Fulcrum text panels now display the line number in the same font as selected for text viewing.

Fulcrum geometry view now has a 'Show view origin' button allowing users to place a cross-hair at the origin of the view plane, which can be helpful for zoom to a certain region of the geometry.

Data files that include reaction names now also include the reaction identifier (MT) number in the identifier, which is also shown in the plot legend. For example: u-235 mt=18 fission. This applies to many data formats including multigroup and continuous-energy cross sections, sensitivity data files, covariance data, etc.

Fulcrum now provides a highlighting all instances of selected text within an editor to help users recognize patterns of use. This highlighting looks like a shadow box surrounding each additional occurrence.

Fulcrum now supports in-line mathematical expression evaluation in any text file. Selected functions and expressions can be evaluated by clicking Edit -> Evaluate or by using the CTRL+E key (CMD+E on Mac) combination. In addition to basic arithmetic operators (+, -, ‘*’, /, ^), the following functions are available for evaluation: sqrt, cos, sin, root, abs, min, max, avg, sum, mul, floor, ceil, exp, log, logn, log10, hyp, ifFunction, clamp, inrange, sign, deg2rad, tan, equal, acos, asin, atan, cosh, tanh, sec, csc, cot, sinh, round, roundn, d2g, g2d, r2d

Several issues with the previous version of Fulcrum were also addressed.

With multiple documents open, file actions (Find, Auto-complete, Save As, etc.) now operate on the expected file.

Fulcrum now displays the sensitivity data file (.sdf) energy-integrated k-eff sensitivity.

Fulcrum's geometry XZ and YZ MeshView 2D plot creation has been updated to correctly set the voxel index at which to create the 2D plot. The results of previous calculations are not affected, but visualization of results may result in minor offsets of data that use the Z-plane. Mouse hover operation now incorporates the mesh voxel index in the info label in addition to the absolute (x,y,z) cartesian coordinates, unit, and material.

Fulcrum now provides the user a warning message when closing a message or editor view with a running job attached to it.

An empty cell data block no longer produces a validation error.

SCALE input parsing (the form of the input) and validation (correctness of input parameters) errors have been disambiguated. Calculations cannot be started for inputs with parse errors, but can be started for inputs with validation errors to obtain additional diagnostic data from the computational codes.

A TRITON timetable density specification with 0 nuclides (indicating all nuclides) no longer produces a validation error in Fulcrum.

Fulcrum syntax highlighting was originally only available for inputs with all lower case keywords. Syntax highlighting is now case-insensitive.

Fulcrum will now correctly validate MCDancoff inputs that start particles in holes, geometry ring regions, and also supports FIDO statements.

The mixing table generation capability (Run/Mixing table) now also supports material aliases.


An issue was resolved on Windows operating systems where very large models would fail to run. 

An issue was resolved in the temperature output edit for multigroup calculations where the nuclide's temperature was listed incorrectly. The results of calculations are not affected.

An issue was resolved on Windows where the KENO plot .png file was not created.

The prompt or total neutrons from fission for continuous-energy calculations (PNU parameter) now properly functions when requested. Previously, only total neutron emissions (prompt+delayed) were used regardless of the parameter setting.

The KENO mean free path edit previously provided the mean distance travelled before a collision or a boundary crossing. In this way, the mean free path depended in part on how the user modeled the geometry. The mean free path has been updated to correctly represent the mean distance between collisions.


An issue was resolved where incorrect gamma yield data were sometimes used in continuous-energy calculations. Testing shows a small decrease (few percent) in flux and response tallies after this update.


An issue was observed where the input keyword 'fluxplanes' was not supported


read fluxplanes


end fluxplanes

Previously, only 'fluxplane', 'fluxplan', and 'flux' were supported in SCALE 6.2.


An issue was resolved when performing restart decay in ORIGAMI when the originating reactor library could not be interpolated to 3.2% enrichment.

The “total” row in an ORIGAMI output of the neutron and gamma emission summary table is now suppressed. In this case, the “total” was of rows of particles/second and percentages, which did not make sense.


Additional backwards compatibility was added for reading SCALE 6.1 and earlier FIDO style input.

The default cutoff criteria for (alpha,n) sources has been changed from 1e-5 to 0 (no cutoff) based on the recommendation and experience of Rick Migliore of AREVA, who noticed that there can be 15% error in some cases in the (alpha,n) component of the total neutron source with the previous default cutoff of 1e-5. With the current implementation, the runtime increase incurred by using a zero cutoff instead of 1e-5 is negligible. 

An issue was resolved in ORIGEN's beta principle emitter summary, which in the table formatting portion of the output, accessed an out-of-bounds array element which sometimes caused a crash.

An issue was resolved in calculating the time step when isotopics where loaded from an f71 file and simultaneously the user specified a start time of zero in the time block. The output file does show the actual time steps used in the calculation. The bug was fixed and additional inputs were added to control the material timeline and time specification.


An issue was resolved in Polaris where the use of size=2 for large water holes could sometimes cause the calculation to terminate.

The Polaris MOC transport solver has been enhanced. PN calculations are supported, with P2 treatment the new default scattering order. The accuracy of LWR reflector calculations is significantly improved with the addition of anisotropic scattering. Transport cross section edits have also been improved by computing hydrogen transport cross sections using the neutron-leakage-correction method.


Sampler was updated to enable multi-dimensional parametric studies to study the effects of combinations of variables on various responses. Using the READ PARAMETRIC block, a user may enter one or more variables that have been defined with uniform distributions along with the number of samples of each variable. Each variable is sampled with uniformly spaced values from its minimum to maximum value.

Sampler generates a summary table of the parametric study, including values for which the minimum and maximum of each response occurs. Sampler also generates PTP plot files showing the dependency of each response on each variable.

SCALE Runtime Environment

An issue was resolved where the HTML icon graphics were not being properly copied to the htmd directory.

Standard Composition Processing

SCALE was updated to provide improved warning messages for nuclides that are not present on the specified cross section data library. Several warnings can be observed with models with multiple compositions containing oxygen. Oxygen contains 0.2% at of O-18, which is not available in ENDF/B-VII.0 or ENDF/B-VII.1. The user can now export the environment variable MISSING_NUCLIDE_MSG_LEVEL=QUIET to reduce the amount of information printed for nuclides that are missing from the cross section library. The calculation continues with the nuclide removed from the model which will produce identical radiation transport and very similar activation/depletion results as using a cross section of 0.0 for each of the missing nuclide(s).

The material processor now supports the legacy SOLN formatted solution composition input that was supported in SCALE 6.1.


Two issues were resolved for T-DEPL calculations using the ASSIGN function. The ASSIGN function now updates the material concentrations correctly, and mass and volume edits of these materials in the system mass table are now correctly computed. All SCALE 6.2 T-DEPL calculations using ASSIGN should be reanalyzed with the SCALE 6.2.1.

Two issues were resolved in T-DEPL calculations using the new timetable SWAP feature. The timetable swap logic introduced time steps too close to one another causing some jobs to fail. The power normalization logic did not account for the swapped materials. All SCALE 6.2 T-DEPL calculations using SWAP should be reanalyzed with the SCALE 6.2.1.

An issue was resolved in multigroup depletion calculations where ADDNUX nuclides were missing their titles in output edits. The results of calculations are not effected.

An issue was resolved in KENO-based TRITON calculations where the geometry volume was being recalculated for each depletion step. The results are not affected, but the calculation efficiency is improved.

ALIAS expansion is now available in KENO-based TRITON calculations.


The job information data imbedded in sensitivity data files (.sdf) from TSUNAMI-3D continuous-energy calculations has been updated to provide the expected data.

SAMS mixture numbers that are longer than 4 digits are now printed in various sensitivity edits. This issue was a holdover from previous SCALE releases where mixture numbers could not exceed 2147.

Total Sensitivity Coefficients by Nuclide and Total Sensitivity Coefficients by Mixture are now displayed for all mixtures.


An issue was resolved were temperature interpolation could sometimes generate a negative cross section for Th-232.  

A cell data issue was addressed where changing the origin of the zone definition in a multiregion model caused the calculation to fail.  

An issue was resolved where using upper-case CE library name caused the problem to not run.

The default settings for legacy standalone (FIDO input) CENTRM calculations have been updated for consistency with XSProc-based CENTRM.

An issue was resolved where Double Heterogeneity calculations failed when CELLMIX was used.

An issue was resolved in CENTRM when using npxs=0 and nfst=6 where CENTRM would fail.

An issue was resolved in depletion calculations where memory grew per depletion step when running CENTRM with a user-input Dancoff factor specified.

The CENTRM "iterp" temperature interpolation message is now correctly identified as a warning (not an error) and limited to one occurrence per calculation.

Multigroup calculations involving multiregion cells with invalid zone radii (equal radii for more than one zone) produced a misleading 'lbar is zero' error. This message has been updated to indicate the line and column of both offending cell radii.

An issue was resolved with the thermal calculation routine using the CENTRM 2D MOC solver option (npxs=6). The impact on criticality calculations for SCALE sample input problems was very small.  Calculations with other npxs values are not affected.  

The MOC solver was also updated to use equal-volume radial mesh for discretizing each material zone. Previous versions of the MOC solver used equal-radii radial mesh. Although the equal-volume radial mesh is more appropriate, this code change has little impact on the accuracy of self-shielded calculations.


The AMPX code PUFF for generating multigroup cross section covariance data has been modernized and enhanced. PUFF has been rewritten in C++ to take advantage of the new C++ reading routines for ENDF (which will also support the new GND format), the new in-memory input/output resource for the COVERX file format, and the new resonance processing application program interface (API). In addition the new PUFF version adds covariance matrices for redundant reaction if not given by the evaluator (e.g. absorption reaction when fission and capture are provided). The processing for fission spectrum (chi) covariance matrices, previously available in a different module has been incorporated into PUFF.

Errors found in the old version of PUFF that affected some test libraries that where not distributed with SCALE have been corrected and results from previous and updated codes have been compared and found to be in good agreement except in cases where erroneous covariance matrices were previously computed.

A new key-word based input with more options has also been added, however, the old FIDO-style input is still supported.

Error reporting has been enhanced to report inconsistencies in the data.

Y12 (AMPX)

A memory defect was resolved in the AMPX Y12 module which would sometimes cause calculations to fail.

Build Instructions

SCALE compilation requires CMAKE 3.3 or higher. See ReadMe file for details.