BUTTERCUP: A Dual Layer Photon Buildup Factor Code
Los Alamos National Laboratory, Los Alamos, NM, USA
Fortran95, Excel, PC running Windows and Linux (C00779MNYCP00).
Buttercup calculates photon dose and exposure buildup factors for several energies and material configurations of interest for two-layer shields based on a previously developed analytical fit formula. The package also contains spreadsheets of the buildup factors to which the formula was fit.
The buildup factors were calculated for 7 energies of interest and various combinations of 4 materials. For each configuration, thicknesses of the shields ranged, in 1 mfp increments, from 2 to 20 total mean free paths. Thus 100 calculations were made per configuration per energy so that the result was a 10 x 10 matrix of responses.
Included data was fit using one of three different methods, and sometimes a combination of methods. First, the buildup data for an entire range of mean free paths were fit to the formula. This worked fine for most cases. However, photons around 100 keV incident on shields involving lead have a much higher buildup, so the second fit method was to fit the log-transformed buildup for these cases. In these cases the fit produces the logarithm of the buildup factors. If Buttercup is used, this can be disregarded as the code performs the exponentiation. The diagnostics for these cases were performed by comparing the anti-logarithms of the formula values to the buildup data. The third method was to break each data set into two smaller sets that would be easier to fit. The two sets were referred to as low material 2 and high material 2, where “low material 2 fit” refers to a shield of 1-10 mfp of the first material followed by 1-5 mfp of the second material and “high material 2 fit” refers to a shield of 1-10 mfp of the first material followed by 5-10 mfp to the second material. This method also included several log fits.
On the order of a few seconds.
PC or Workstation
Windows or Linux Operating System, with a Fortran95 compiler installed. The code was tested with Intel 11.1 and GFORTRAN 4.4.5.
a.) Included Documentation:
A. Davis, et al. “Buttercup: A Dual-Layer Photon Buildup Factor Code,” ReadMe documentation (March 2011).
b.) Background Reference:
A. Davis, et al. “Photon Buildup Factors in Laminated Dual-Layer Shields,” Nucl. Technol., 2011: 270-288.
The package is transmitted on CD and includes the executable, the source code, the libraries (formatted for use), and a Microsoft Excel file with all of the buildup factors and parameters for the fit formula used in the code and the referenced documents.
KEYWORDS: PHOTON, BUILDUP FACTOR