1. NAME AND TITLE

SKYSHINE-KSU: Code System to Calculate Neutron and Gamma-Ray Skyshine Doses Using the Integral Line-Beam Method.

DATA LIBRARY: SKYDATA-KSU: Approximate Beam Response Functions for Gamma-Ray and Neutron Skyshine Analysis.

2. CONTRIBUTOR

Kansas State University, Manhattan, Kansas.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; IBM PC (C00646/IBMPC/03).

4. NATURE OF PROBLEM SOLVED

This package includes the SKYNEUT 1.1, SKYDOSE 2.3, MCSKY 2.3 and SKYCONES 1.1 codes plus the DLC-188/SKYDATA library to form a comprehensive system for calculating skyshine doses. See the author's web site for related information: http://athena.mne.ksu.edu/~jks/

SKYNEUT evaluates the neutron and neutron-induced secondary gamma-ray skyshine doses from an isotropic, point, neutron source collimated by three simple geometries: an open silo, a vertical black (perfectly absorbing) wall, and a rectangular building. The source may emit monoenergetic neutrons or neutrons with an arbitrary multigroup spectrum of energies.

SKYDOSE evaluates the gamma-ray skyshine dose from an isotropic, monoenergetic, point gamma-photon source collimated by three simple geometries: (1) a source in a silo, (2) a source behind an infinitely long, vertical, black wall, and (3) a source in a rectangular building. In all three geometries an optional overhead slab shield may be specified.

MCSKY evaluates the gamma-ray skyshine dose from an isotropic, monoenergetic, point gamma-photon source collimated into either a vertical cone (i.e., silo geometry) or into a vertically oriented structure with an N-sided polygon cross section. An overhead laminate shield composed of two different materials is assumed, although shield thicknesses of zero may be specified to model an unshielded SKYSHINE source.

SKYCONES evaluates the skyshine doses produced by a point neutron or gamma-photon source emitting, into the atmosphere, radiation that is collimated into an upward conical annulus between two arbitrary polar angles. The source is assumed to be axially (azimuthally) symmetric about a vertical axis through the source and can have an arbitrary polyenergetic spectrum. Nested contiguous annular cones can thus be used to represent the energy and polar-angle dependence of a skyshine source emitting radiation into the atmosphere.

5. METHOD OF SOLUTION

The SKYNEUT calculation of the skyshine doses uses the integral line-beam method which is based on a newly developed three-parameter approximation of the neutron line-beam response functions.

SKYDOSE is based on the integral line-beam method. For shielded sources, an approximate method is used based on exponential attenuation with buildup in the shield.

In MCSKY the skyshine dose calculation is based on a Monte Carlo algorithm to evaluate the gamma-ray transport through the source shields and the integral line-beam method to describe the subsequent transport of gamma photons through the atmosphere.

In SKYDOSE the skyshine dose calculation uses the integral line-beam method based on a three-parameter approximation of neutron and gamma-ray line-beam response functions.

6. RESTRICTIONS OR LIMITATIONS

For SKYNEUT source neutron energies must be between 0.01 and 14 MeV. For energies above 1 MeV, source-to-detector distances can be as great as 2500 m. For source energies below 1 MeV, the maximum source-to-detector distance is somewhat less. Fluence-to-dose conversion factors are from ICRP Report 51, but do *not* include the factor of 2 increase in the neutron quality factor recommended at the 1985 Paris meeting of the ICRP.

For SKYDOSE the source energy E must be between 0.02 and 100 MeV, except for sources with an overhead shield, for which case 0.02 <= E <= 10 MeV. The maximum source-to-detector distance is 3000 m for E <= 10 MeV and 1500 m for higher energies.

For MCSKY the source energy may be any energy between 0.02 and 100 MeV. In the Monte Carlo shield calculation, positron transport and bremsstrahlung production are neglected, although the air transport calculation using the line-beam response function does include these components. Consequently, for heavily shielded sources with energies above about 20 MeV, McSKY results must be used cautiously especially at detector locations near the source where shield-generated bremsstrahlung may be significant. The maximum source-to-detector distance is 3000 m for E <=10 MeV and 1500 m for higher source energies.

In SKYCONES source neutron energies must be between 0.01 and 14 MeV. For energies above 1 MeV, source-to-detector distances can be as great as 2500 m. For source energies below 1 MeV, the maximum source-to-detector distance is somewhat less. For gamma photons, the maximum source-to-detector distance is 3000 m for photon energies between 0.02 and 10 MeV and 1500 m for photon energies between 10 and 100 MeV. For neutron sources, both the neutron skyshine dose and the secondary photon dose from neutron interactions in the air are computed separately.

7. TYPICAL RUNNING TIME

SKYNEUT and SKYDOSE run quickly, requiring only a few seconds per detector location and per source energy group on an IBM PC/P5 (66 MHZ).

The McSKY running time depends primarily on computer speed and number of source particle histories to be followed in the shield, and to a lesser extent on the shield thicknesses and the complexity of the source collimation. A calculation involving a 3 mfp-thick shield over a silo with 50,000 source particles requires about 30 seconds on an IBM PC/P5 (66 MHZ).

8. COMPUTER HARDWARE REQUIREMENTS

IBM PC and compatibles. These codes can be easily ported to almost any computer with a FORTRAN 77 compiler.

9. COMPUTER SOFTWARE REQUIREMENTS

The codes were written in FORTRAN 77 and were tested on an IBM compatible PC. Executable files produced by the Microsoft FORTRAN compiler (version 5.1) are included for McSky and Skyneut codes. Included Skydose and Skycones executables were created on a Pentium/120 under Windows95 using the Lahey 90 Fortran compiler.

10. REFERENCES

a. included in documentation:

RSICC, "README.TXT" (November 16, 2000).

J. K. Shultis, R. E. Faw and F. A. Khan, "SKYNEUT: A Code for Neutron Skyshine Calculations Using the Integral Line-Beam Method," KSU Report 9503 (Revised January 1997).

J. K. Shultis, R. E. Faw and R. C. Brockhoff, "SKYDOSE: A Code for Gamma Skyshine Calculations Using the Integral Line-Beam Method," KSU 9902 (Revised June 1999).

J. K. Shultis, R. E. Faw and M. H. Stedry, "McSKY: A Hybrid Monte-Carlo Line-Beam Code for Shielded Gamma Skyshine Calculations," KSU 9501 (Revised October 1997).

J. K. Shultis, "SKYCONES: A Code for Neutron and Photon Skyshine Calculations from Annular Conical Sources," KSU 9903 (June 1999).

J. K. Shultis, R. E. Faw, A. A. Gui, and R. C. Brockhoff, "Approximate Beam Response Functions for Gamma-Ray and Neutron Skyshine Analysis," KSU Report 271 (June 1995).

b. background information:

A. A. Gui, "Response Functions for Neutron Skyshine Analyses, PhD Dissertation," Kansas State University, Manhattan, KS 66506 (1994).

J. K. Shultis, and R.E. Faw, "Extensions to the Integral Line-Beam Method for Gamma-Ray Skyshine Analyses," Report SAND94-2019 (1995).

J. K. Shultis, R. E. Faw and M. S. Bassett, "The Integral Line- Beam Method for Gamma Skyshine Analysis," Nuclear Science and Engineering, 107, 228-245 (1991).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents in 10.a and one 3.5-in DS/HD (1.44MB) diskette written in a self-extracting compressed DOS file containing source codes, executable files, response function data files, documentation and files for input and output of example problems.

12. DATE OF ABSTRACT

July 1996, revised June 1997, January 1998, November 2000.

KEYWORDS: SKYSHINE; GAMMA-RAY; NEUTRON; MONTE CARLO; AIR TRANSPORT; INTERACTIVE; MICROCOMPUTER