1. NAME AND TITLE
SHIELDOSE: Code System for Space Shielding Radiation Dose Calculations.
U.S. National Bureau of Standards, Washington, D. C.
Nuclear Energy Agency Data Bank, Gif-sur-Yvette, France.
Experimental and Mathematical Physics Consultants, Gaithersburg, Maryland
3. CODING LANGUAGE AND COMPUTER
Fortran 77; IBM 3084Q, VAX-11/780, CYBER-740 (A); IBM PC (B).
4. NATURE OF PROBLEM SOLVED
SHIELDOSE evaluates the absorbed dose within a spacecraft due to a specified radiation environment as a function of depth in aluminum shielding material of spacecraft, given the electron and proton fluences encountered in orbit. It calculates, for arbitrary proton and electron incident spectra, the dose absorbed in small volumes of the detector materials Al, H2O (tissue-equivalent detector), Si, and SiO2, in the following aluminum shield geometries:
(1) in a semi-infinite plane medium, as a function of depth;
(2) at the transmission surface of a plane slab, as a function of slab thickness; and
(3) at the center of a solid sphere, as a function of sphere radius.
Such data are particularly suitable for routine dose predictions in situations where the geometrical and compositional complexities of the spacecraft are not known. Restricting consideration to these rather simple geometries has allowed for the development of accurate electron and electron-Bremsstrahlung data sets based on detailed transport calculations rather than on more approximate methods.
5. METHOD OF SOLUTION
SHIELDOSE makes use of precalculated, monoenergetic depth-dose data for an isotropic, broad-beam fluence of radiation incident on uniform aluminum plane media. These data are in a scaled form so as to facilitate accurate interpolation used in the integration over the incident spectra. The conversion of slab dose to dose at the center of a sphere is done using a relation involving derivatives of the depth-dose curve, which is strictly valid only in a straight-ahead approximation. All the necessary interpolation and differentiation is accomplished through the use of natural-cubic-spline fits to the numerical data.
The quantity of interest calculated by SHIELDOSE is the absorbed dose as a function of depth in an aluminum shield for an arbitrary incident fluence of radiation. The incident fluence can be either protons or electrons. If it is protons, it will be implicitly understood that the absorbed dose is the proton dose; if electrons, the absorbed dose is calculated separately for the Bremsstrahlung component and the "electron" component (i.e., the distribution of deposited electron energy never converted to Bremsstrahlung photons). Results are calculated for three geometries.
6. RESTRICTIONS OR LIMITATIONS
Due to the extent of the data base, the energies of the incident radiation are restricted to the regions 2 to 5000 MeV for protons and 0.02 to 20 MeV for electrons. These energy regions are more than adequate for problems involving the terrestrial radiation environment. This version of the code system calculates the dose at no more than 50 depths in the shield.
It is generally necessary to suppress underflow diagnostics which interrupt, and can eventually terminate, a run. Underflow conditions are not detected by the code itself and should therefore be suppressed using the appropriate options available at the particular computing installation. For the IBM system this is accomplished by the "CALL ERRSET" instruction at the beginning of the main routine.
7. TYPICAL RUNNING TIME
The sample problem executed in 6 seconds on the IBM 360/91. Approximately 10 seconds are required for setting up internal matrices and approximately 1 second for each input proton and electron spectrum set.
For the IBM PC version, the sample problem SELTZER.DAT took about 10 minutes on an IBM PC/XT with a math co-processor.
8. COMPUTER HARDWARE REQUIREMENTS
The code is operable on the IBM 3084Q, VAX-11/780, and CDC CYBER 740 computers and also IBM PC. It uses standard I/O plus 1 storage media.
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran 77 compiler is required. For the PC version MICROSOFT Fortran Version 4.01 or higher may be used.
S. Seltzer, Addendum to NBS Technical Note 1116, "SHIELDOSE: A Computer Code for Space-Shielding Radiation Dose Calculations" (February 1984).
S. Seltzer, "SHIELDOSE: A Computer Code for Space-Shielding Radiation Dose Calculations," NBS Technical Note 1116 (May 1980).
T. Jordan, "SHIELDOSE FOR THE PC," informal notes, Experimental and Mathematical Physics Consultants, Maryland, 1990.
11. CONTENTS OF CODE PACKAGE
Included are the referenced documents and one (1.2MB) DOS diskette which contains the source code, job control language for the 3 hardware versions, a depth dose data library, and sample problem input and output. For the IBM PC version, one double-sided double density diskette, 5.25-in (360KB), is enclosed.
12. DATE OF ABSTRACT
February 1982; revised March 1982, February 1983, December 1987; October 1990.
KEYWORDS: KERNEL; BREMSSTRAHLUNG; ELECTRON; SPACE RADIATION; SLAB; SPHERICAL GEOMETRY; PROTON; MICROCOMPUTER