Scale 6.1 Known Issues

Since Scale 6.1 was released on July 22, 2011, end users and the Scale development team have identified a few issues that impact the performance of the code package. To keep users informed of the latest information, items are cataloged here. Further information and discussion opportunities are available in the SCALE 6 User Notebook maintained by RSICC (http://scale.ornl.gov/notebooks.shtml). These known issues will be corrected in the next release of Scale and possibly in a patch to this release. Possible user corrections or workarounds are noted below.

Error in ENDF/B-VII.0 Decay Data

An error in the nuclear decay data for 234Th has been identified in ENDF/B-VII.0, which is used for the SCALE decay library. A review of the problem indicates that the error was introduced in the evaluated ENDF/B-VII.0 decay sub-library released by the National Nuclear Data Center (NNDC) in December 2006. The NNDC has confirmed the problem and recently released an updated decay library with ENDF/B-VII.1. Currently, ORNL is working closely with NNDC to identify the nature and extent of the nuclear data evaluation problem and is preparing a patch for the ENDF/B-VII.0-based decay library distributed with SCALE 6.1. It is important to note that ORNL has performed extensive validation using the ENDF/B-VII.0-based decay library in SCALE 6.1 and has NOT identified any discrepancies for benchmark problems involving irradiated fuel isotopic compositions, decay heat, and source terms. The error has been observed for problems involving the decay of 238U. As an example, the gamma ray spectra calculated using SCALE 6.0 (ENDF/B-VI decay data) and SCALE 6.1 (ENDF/B-VII.0 decay data) are shown in the following plot. The spectrum obtained using ENDF/B-VII.0 data is significantly over estimated, caused primary by incorrect production of 234Pa from 234Th decay. Additional information on the error in ENDF/B-VII.0 should be posted on the NNDC website (http://www.nndc.bnl.gov/) in the near future.


Comparison of gamma ray spectrum for the decay of low-enriched uranium fuel after
10 years cooling (SCALE 6.0 in red and SCALE 6.1 in blue).

Date Identified: March 18, 2012

Minor Issues Identified with Fixed-Source Monte Carlo Capabilities

A few minor issues were identified with the SCALE fixed-source Monte Carlo code Monaco and an associated utility, especially related to seldom-used optional features. These features will be corrected in a pending patch for SCALE. These features should be used with caution until the patch is applied.

  • When specifying the special distribution pwrNeutronAxialProfileReverse or pwrGammaAxialProfileReverse for a spatial source distribution, the un-reversed profile is erroneously returned.

    Impact: This is a seldom-used feature that was implemented for compatibility with previous MORSE calculations. Problems run using one of the special axial distributions containing the word reverse are in fact not reversed, and erroneous results could result due to an inaccurate source specification.

  • The sum of the point detector group-wise results may be higher than the point detector energy-integrated (total) results. The reported total is correct. The group-wise values are high due to rejecting negative contributions (which happen a small fraction of the time due to the multi-group energy/angle physics).

    Impact: The energy-integrated results are correct. Only energy-dependent results are in error for some calculations. If the use of energy-dependent results is desired, users should verify that they sum to the total value.

  • If a source specification utilizes different Watt spectra distributions in multiple sources, the energies sampled for one source may include energies from the wrong distribution.

    Impact: Only models that implement more than one Watt spectrum are impacted. Since Watt spectra from different isotopes are quite similar, the impact of this discrepancy may not be noticeable. For Watt spectra that are very different, results may differ.

  • The utility program mim2wwinp does not format MCNP *.wwinp files correctly for photon-only problems. MCNP interprets a *.wwinp with only one particle listed as neutrons, even in a "mode p" problem. The *.wwinp file produced by SCALE needs to specifically identify that there are 0 neutron groups for photon-only problems.

    Impact: Subsequent MCNP calculations that use the SCALE generated .wwinp files for photon-only problems will not run.

    • Date Identified: 3/22/2012
    Reference: Page 79 of SCALE 6 User Notebook

    Discrepancy Observed with Small Number Densities with 44-Group ENDF/B-V Data and CENTRM

    An issue has been identified that can lead to non-conservative keff values when using the 44-group ENDF/B-V data with CENTRM for high-leakage models with trace-element number densities below ~10-9 atoms/barn-cm when running SCALE 5.1 – SCALE 6.1. The effect on the 238-group ENDF/B-V,VI, and VII libraries is minimal. There is no effect on continuous-energy Monte Carlo calculations.

    In the dozens of test cases examined thus far, the discrepancy is only realized in cases that meet ALL of the following conditions:

    1. The number density of at least one nuclide has a small fractional concentration of 10-8 or less relative to the total mixture number density. Typically this corresponds to an absolute concentration less than ~10-9 to 10-10 atoms/barn-cm, but greater than zero.
    2. The SCALE 44-group ENDF/B-V library or a user-generated broad group library with few groups in the U-238 resolved resonance range (1 eV-4 KeV) is used.
    3. CENTRM is used for resonance self-shielding. This is the default behavior in SCALE 6.1, but NITAWL processing is the default behavior for SCALE 5.1 and 6.0 for the ENDF/B-V cross-section data, so the user must explicitly request CENTRM processing to observe the discrepancy with SCALE 5.1 or 6.0.
    4. The system is sensitive to the high-energy portion of the resolved range, which most commonly occurs for high leakage systems. Low-leakage criticality and depletion models examined realized only a minimal impact.
    5. Calculations are performed with SCALE 5.1, 6.0 or 6.1.

    Impact on calculations:

    1. Continuous-energy KENO calculations do not use CENTRM and are not affected.
    2. The impact for all 238-group calculations examined thus far is small, on the order of a few pcm.
    3. Eigenvalues and isotopic concentrations computed for the 44-group ENDF/B-V depletion cases examined are not significantly affected, as these are low-leakage systems [reflected lattice geometries]. For most cases that meet all of the above criteria, including burned fuel criticality safety calculations that include small concentrations of fission products, the discrepancy introduces an error on the order of 100 pcm.
    4. In a contrived case that artificially introduces a trace material into a plutonium nitrate system, a discrepancy of ~3% delta-k was observed. This is the maximum discrepancy observed for the real and hypothetical systems examined thus far, but it should not be considered a bounding value.

    Corrective Action

    1. The SCALE Team is developing a patch that corrects this issue.
    2. Users should examine calculations to determine if they meet the criteria provided above.
    3. The eigenvalue for suspect systems should be examined using a different library, such as the 238-group ENDF/B-V to determine if a particular system is impacted.
    4. Users should install the SCALE 6.1 patch when it is available and repeat any suspect calculations.

      5. Date Identified: 1/9/12
      Reference: Page 78 of SCALE User Notebook
      Acknowledgement: This issue was first identified by SCALE user Dale Lancaster

      Optional Output Edit in STARBUCS

      In STARBUCS burnup credit loading curve search calculations, an optional input prt=short may be used within the READ SEARCH input block to restrict the final output to contain only relevant information for a burnup loading curve calculation. In SCALE 6.1, this optional input causes the calculation to crash.

      Users should only use the default parameter prt=long, which retains all SCALE output information for the last step of the iterative fuel enrichment search process. As prt=long is the default option in STARBUCS, there is no need for this input option to be specified in a STARBUCS input file.

      Date Identified: 2/10/2011
      Reference: Page 77 of SCALE 6 User Notebook

      MacOS System Requirements

      The SCALE 6.1 Readme states that the system will operate on Mac OSX version 10.5 or newer, where Mac OSX 10.6 or newer is actually required to properly execute SCALE 6.1.

      The symptoms are such that the SCALE runtime will execute and a job banner will be produced, but the executable modules will fail.

      If messages are turned on (-m flag on the batch6.1 command) the following message will be reported:

      'dyld: unknown required load command 0x80000022'

      The solution is to upgrade to Mac OSX 10.6 or newer.

      Date Identified: 2/23/2012
      Reference: Page 76 of SCALE 6 User Notebook

      Windows ORIGEN and OPUS Sample Problems

      There has been an issue identified when running the ORIGEN and OPUS sample problems on Windows.

      Specifically, the sample problems' shell script uses an invalid path when attempting to copy needed resources into the working directory. Without these needed resources, both sample problems fail to produce the expected results.

      The fix is simple. For the origen.input and opus.input files, located in
      scale6.1\smplprbs\Windows, replace

      =shell
      copy z:\scale_staging\data\arplibs\w17_e40.arplib ft33f001
      end

      with

      =shell
      copy %DATA%\arplibs\w17_e40.arplib ft33f001
      end

      Date Identified: 8/30/2011
      Reference: Page 70 of SCALE 6 User Notebook

      Unable to access jarfile ... ScaleDiff.jar

      There has been an issue identified where when running the sample problems,
      the ScaleDiff.jar file is not found producing an 'Unable to access jarfile ... ScaleDiff.jar' message.

      The issue is due to not having the source code installed.

      The ScaleDiff-Samples.xml zip file contains the following:
      • samples.xml
      • ScaleDiff.jar

      Do the following to update your Scale6.1 install

      1. Extract the contents into your Scale6.1 directory. You will be prompted to ‘copy and replace’ your samples.xml file.

      2. Move the Scale6.1\ScaleDiff.jar file into your Scale6.1\cmds directory. You will be prompted ‘copy and replace’ your ScaleDiff.jar file.

      The updated Scale6.1\samples.xml, and Scale6.1\cmds\ScaleDiff.jar files should be available to verify Scale as detailed in the readme file.

      Updated: 11/15/2011
      Reference: Page 71 of SCALE 6 User Notebook

      table_of_content_*.txt: no such file or directory

      When running the sample problems an error may occur similar to the following,

      C:\Scale6.1\Windows_amd64\bin\grep: table_of_content_*.txt: No such file or directory

      This is due to a typo in the scale\samples.xml file.

      'table_of_content_*' should be 'table_of_contents_*'. Notice the extra 's'.

      Edit your Scale\samples.xml file, find 'table_of_content_*' and replace with 'table_of_contents_*'.

      Date Identified: 10/6/2011
      Reference: Page 72 of SCALE 6 User Notebook

      ORIGEN 200-group cross section library

      A problem was identified in the energy-group boundaries of the ORIGEN 200-neutron-group cross-section library, origen.rev02.jeff200g. The boundaries were generated with constant lethargy instead of the boundaries of the SCALE 200-group transport library. Use of this library is currently not recommended, as it will produce erroneous results. An update to the library will be available soon.

      Date Identified: 10/24/2011
      Reference Page 73 of SCALE 6 User Notebook

      ORIGEN natural isotopic abundances

      The natural isotopic abundances for several elements in the ORIGEN library are incorrect. The abundances have been corrected and an updated library will be available soon. The use of natural isotopic abundances (NEX1=4) for input element concentrations enter in gram units may result in incorrect isotopic concentrations for Mg, Ge, Kr, Sr, and Te. If atom units (gram atoms) are used, incorrect isotopic concentration may occur for F, Na, Mg, Al, P, Sc, Mn, Co, Ge, As, Kr, Sr, Y, Nb, Rh, Te, I, Cs, Pr, Tb, Ho, Tm, and Au.

      Date Identified: 10/24/2011
      Reference: Page 74 of SCALE 6 User Notebook

      Problem with thermal energy cutoff in continuous-energy KENO calculations

      Internal testing of continuous-energy calculations with KENO has revealed a considerable non-conservative change in keff, on the order of 20%, for cases involving BeO. Users who properly validate continuous-energy KENO calculations for these systems would notice a strong systematic bias for bound BeO cases prior to use in safety calculations. Nevertheless, users should not use be-beo in continuous-energy KENO calculations.

      Note that multigroup calculations in KENO are not affected by this issue, and updates to the continuous-energy data for bound BeO will be available soon.

      Further explanation:

      Scale continuous energy neutron cross-section libraries are based on ENDF/B-VI Release 8 and ENDF/B-VII Release 0. While most of the neutron cross sections are for nuclides that are assumed to be free (not bound in a molecule), some nuclide cross sections are for bound nuclei that are commonly referred to as s(a,b) cross sections or thermal kernels. Hydrogen bound in water or Be in BeO are some example nuclei that have bound thermal cross sections. Scale continuous-energy neutron cross-section libraries were generated by processing the ENDF thermal kernel data for incident neutron energies of 5.05eV or below. To provide flexibility in analysis without the need to regenerate the cross section library, KENO was designed to implement a user-selectable value for the thermal cutoff for s(a,b) treatment, with default neutron cutoff energy of 3eV. Above this cutoff the effects of thermal motion of the molecule are assumed to be negligible.

      As a result of a recent internal testing, it was discovered that KENO does not apply the thermal cutoff value to the use of s(a,b) treatment. If the evaluation does not have data up to 5.05eV, the short collision time method is used to extend the incoherent inelastic scattering data up to 5.05eV. Coherent elastic scattering is generated only for the energy range specified in the ENDF file. It was discovered that for Be in BeO, the coherent elastic and incoherent inelastic scattering cross sections extended beyond 3eV but did not have the same upper cut-off value. When KENO ignores the default thermal cut-off value of 3eV, it tries to sample from both coherent elastic and incoherent inelastic and obtains the wrong cross section between the cut-off values of these reactions.

      Date Identified: 10/25/2011
      Reference: Page 75 of SCALE 6 User Notebook