SCALE 5.1 TRITON/NEWT/PMC Update                              19 March 2007
                                                      Updated: 25 June 2007

 (Also includes updates for CSAS, TSUNAMI, and other control modules)

NOTE: This download is recommended for all SCALE 5.1 users.

The following updates have been made to the Material Information
Processor Library (MIPLIB) in SCALE: 

   (1) MIPLIB has been updated to terminate execution with an error message
   if the ENDF/B-VI V6-238 library is specified with NITAWL as the
   resonance self-shielding module. Because the Reich-Moore resonance
   parameters were omitted from the 238-group ENDF/B-VI library, NITAWL
   will pass infinitely dilute cross sections for nuclides that have
   Reich-Moore parameters in ENDF/B-VI.

   (2) MIPLIB has been updated to reduce the memory and CPU time
   requirements in the PMC module (which generates multigroup cross
   sections from the CENTRM continuous energy data) when large number of
   nuclides in very small concentrations are included in the model (e.g.,
   fission products in spent fuel). PMC can spend a significant amount of
   time and require large amounts of memory in preparing weighted
   multigroup cross sections for such nuclides. However, these low density
   nuclides are effectively infinitely dilute and can be treated as such
   and omitted from PMC processing. Those nuclides that have a fractional 
   nuclide density less than the specified cutoff will be omitted from the 
   PMC calculation and treated as infinitely dilute. The default cutoff value
   is 1E-8 in TRITON and 0.0 in CSAS and TSUNAMI (i.e., no cutoff), but this
   value can be overridden by user input ("PMC_CUTOFF=" in the CENTRM DATA 
   input block for each unit cell). 

These updates to MIPLIB affect most control modules in SCALE, including
CSAS, CSAS6, TRITON, TRITON6, TSUNAMI-1D and -3D.

Note that the PMC cutoff in TRITON and TRITON6 is assessed at each time
step, such that nuclides that are initially present in trace quantities
but build up with depletion are automatically added to PMC calculations
once their concentrations exceed the cutoff value.

TRITON and TRITON6 were also modified to automatically adjust the number
of libraries per cycle if the user-supplied value is too small for the
cycle length.

NEWT has been updated to fix a problem that occurs in printing the input
summary within T-NEWT calculations in TRITON on Linux based systems.
Additionally, NEWT now supports the use of mixture ID 0 (zero) as a void
mixture, as is permitted in KENO and XSDRN calculations.

PMC was updated to support the MIPLIB update described above. In addition,
PMC was modified to correct a problem with integration of the inelastic
continuous energy cross-section data at the top of the continuous energy
cross-section range. It was possible to produce negative inelastic
cross sections in the first group that contained continuous-energy data,
but only if the user had extended the resolved resonance range in PMC
well above 10 MeV (via the DEMAX parameter), and the problem had a fast
flux distribution.


Installation instructions 
------------------------- 

The updates are now included with the CENTRMST update on 
www.ornl.gov/sci/scale/centrmst_update.htm. See the README file there 
for instructions on how to download and install.