RSICC DATA PACKAGE DLC-224

 

1.   NAME AND TITLE OF DATA LIBRARY

ALBEDO-DATA:      KSU Neutron Albedo Data.

 

2.   NAME AND TITLE OF DATA RETRIEVAL PROGRAMS

            ALBEDOS: A program to evaluate the 24-parameter differential neutron dose albedos using a new

albedo approximation. 

     

3.   CONTRIBUTOR

Kansas State University, Manhattan, Kansas.

 

4.   HISTORICAL BACKGROUND AND INFORMATION

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.

 

5.   APPLICATION OF THE 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.

 

6.   SOURCE AND SCOPE OF DATA

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.

 

7.   DISCUSSION OF THE DATA RETRIEVAL PROGRAM

A Fortran program to evaluate the 24-parameter differential neutron dose albedo using a new albedo approximation is included. 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.

 

8.   DATA FORMAT AND COMPUTER

RSICC ID is D00224MNYCP00. The various tables of fit coefficients for approximating albedo formulas are collected here as ASCII machine readable files. The name of each file refers to the Table number in the report.

 

9.   TYPICAL RUNNING TIME

The ALBEDOS interactive program runs in seconds.

 

10.  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). The data in this report have been extracted from the appendices of the dissertation Calculation of the Albedos for Neutrons and Photons by R.C. Brockhoff, KSU (2003).

 

11.  CONTENTS OF LIBRARY

The data are transmitted in a WinZIP file on a CD. Included in the file are ASCII data files, ALBEDOS code and the referenced document.

 

12.  DATE OF ABSTRACT

January 2007, revised September 2007.

 

KEYWORDS:   ALBEDO DATA