*** BUG Reports and Notices ***
MCNP5-1.51 Corrects Bug in
Photon Calculations of MCNP5-1.50
Los Alamos National Laboratory, Los Alamos, New Mexico, contributed a corrected version of their Monte Carlo
N–particle transport code system. The package includes MCNP5 1.51, MCNPX 2.6.0, and MCNPDATA. Neither MCPX nor
MCNPDATA were modified in this release. The only change is to MCNP5 1.51, which corrects a significant error in
the MCNP5 1.50 photon Doppler broadening routine that can lead to incorrect results.
RSICC will contact recipients of MCNP5 1.50 and will send replacement DVDs. Upon receipt of the new DVD, please
delete all copies of MCNP5 1.50 and shred the original DVD.
Notice: Bug in MCNP5-1.50
Photon Calculations/Patch
January 16, 2009
NOTIFICATION:
MCNP5-1.50 was released by RSICC in December, 2008 as part of RSICC
package CCC-740. Users who received that package should be aware that
there is a significant error in the photon Doppler broadening routine
that can lead to incorrect results. This error occurs on all computing
platforms (Windows/Linux/Mac/Unix).
This error does NOT occur in previous versions of MCNP5 (1.40, 1.30,
etc.), nor does it affect any versions of MCNPX. The error does NOT
affect results for neutron-only criticality calculations, nor any
problems that do not include photons.
Additional details will be posted on the mcnp.lanl.gov website shortly.
IMMEDIATE CORRECTIVE ACTION:
Users of MCNP5-1.50 who compile the code themselves can apply the patch
contained in the attached files. There is a PDF file with instructions
for applying the patch, and also a text file containing the patch.
patch-MCNP5_RSICC_1.50_to_1.51.pdf
patch-MCNP5_RSICC_1.50_to_1.51
Users who do not or cannot patch and recompile the code can disable the
photon Doppler broadening treatment by adding the following card to the
data-cards section of the input:
phys:p 4j 1
FURTHER CORRECTIVE ACTION:
The MCNP team will correct the bug and re-release the code as MCNP5
1.51. This will be conveyed to RSICC for distribution.
RSICC has provided the following advice for users concerning the CCC-740
package:
If you do not have an urgent need for MCNP5 1.50, we request that you
wait until 1.51 is released before ordering the code from RSICC.
Announcement of availability will be posted on the RSICC website and
newsletter. RSICC will send replacement DVDs to all recipients of MCNP5
1.50. No additional action is required to get the replacement DVD, which
will be the new package containing MCNPX 2.6.0, MCNPDATA and the
corrected MCNP5 1.51. Upon receipt of the new DVD, please delete all
copies of MCNP5 1.50 and shred the original DVD. The same license and
export control restrictions to which you agreed for the initial release
apply to the new package.
Questions on this error can be directed to mcnp@lanl.gov for a quick
response.
Thank you,
Jeremy Sweezy
Last Modified: 25-March-2009
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