DLC-0224 ZZ-ALBEDO-DATA.

1. NAME OR DESIGNATION:  ZZ-ALBEDO-DATA.

3. DESCRIPTION

The use of albedo techniques is central to many radiation streaming codes and has been widely used as an alternative to much more expensive transport calculations. Key to the albedo technique is the availability of either a large set of albedo data or, preferably, an empirical formula that approximates the albedo over the range of source energies and incident and exit radiation directions involved in a particular problem. Previously proposed neutron and photon albedo approximating formulas have been based on limited energy-angular ranges, a single reflecting material, old cross section data, and, most important, obsolete fluence-to-dose response functions. This library contains differential neutron dose albedo functions, based on modern cross section and response function data.
  
Newly evaluated parameters are tabulated for several empirical differential dose albedo formulas. The albedos considered are (1) two approximations for photon albedo, (2) a new approximation for the neutron albedo, and (3) the secondary-photon albedo for incident neutrons. Albedo data is provided for four materials: concrete, iron, lead, and water. Unlike previous compilations of albedo data, modern dosimetric units have been employed. Data are presented for (1) the ambient dose equivalent H*(10mm) and (2) the effective dose equivalent for anteroposterior (AP) illumination of the ICRP anthropomorphic phantom.

4. METHODS

Monte Carlo code, MCNP, was used to calculate the albedo reflected from thick slabs of various materials. In particular, a homogeneous cylindrical slab surrounded by a vacuum was used. The incident neutrons were modeled by a point monodirectional source positioned just inside the center of the circular scoring (reflecting) surface. This was done to facilitate scoring because all particles crossing the surface must be outgoing (reflected) particles. Slab thickness and radius were sufficiently large (1000 cm) so that negligible numbers of neutrons were transmitted through the slab or radial surface. Energy of the source neutrons was sampled uniformly over an energy group or from a fission neutron distribution.
  
The MCNP calculated differential dose albedos were used to obtain extensive sets of values for a  wide range of incident energies, incident directions, and reflected directions. To make easy use of these results, empirical approximating functions were sought that could accurately reproduce the calculated albedos. The parameters in these empirical albedos functions were estimated by fitting the approximating functions to MCNP calculated values. A global fit was used that minimized the maximum absolute error between the function and the calculated data.

6. TYPICAL RUNNING TIME:  The ALBEDOS interactive program runs in seconds.

8. RELATED OR AUXILIARY PROGRAMS

ALBEDOS: A program to evaluate the 24-parameter differential neutron dose albedos using a new albedo approximation.
The source code and a Windows executable created with Lahey Fortran 90 are in this distribution. The program reads ASCII data files for the parameter of the albedo approximation. The data files are ASCII files of the tables in the reference.

- R. C. Brockhoff and J. K. Shultis:
Data for the Calculation of Albedos from Concrete, Iron, Lead and Water for
Photons and Neutrons, Kansas State University, Engineering Experiment Station,
Report 301 (Sept. 2005, revised March 2006)

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The various tables of fit coefficients for approximating albedo formulas are collected as ASCII machine readable files.
The data in the report have been extracted from the appendices of the dissertation Calculation of the Albedos for Neutrons and Photons by R.C. Brockhoff, KSU (2003). The name of each file refers to the Table number in the report.

15. NAME AND ESTABLISHMENT OF AUTHORS: Kansas State University, Manhattan, Kansas, USA.

ASCII data files
ALBEDOS code
Electronic document