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[Program Service | Recent programs]

CCC-0360 AIRDIF. (Abstract last modified 24-MAY-1985)


AIRDIF, Neutron and Gamma Doses from Nuclear Explosion by 2-D Air Diffusion

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Abstract Table of Contents:

NAME | COMPUTER | PROBLEM | SOLUTION | RESTRICTIONS | CPU | FEATURES | AUXILIARIES | STATUS | REFERENCES | REQUIREMENTS | LANGUAGE | OPERATING SYSTEM | OTHER RESTRICTIONS | AUTHOR | MATERIAL | CATEGORIES |

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1. NAME OR DESIGNATION OF PROGRAM - AIRDIF. 


2. COMPUTER FOR WHICH PROGRAM IS DESIGNED AND OTHER MACHINE VERSION PACKAGES AVAILABLE -

To request or retrieve programs click on the one of the active versions below. A password and special authorization is required.

Explanation of the status codes.

Program-name         Package-ID  Status
AIRDIF               CCC-0360/01 Tested

Machines used:
Package-ID     Orig.Computer                       Test Computer
CCC-0360/01    CDC 7600                            CDC CYBER 740

3. DESCRIPTION OF PROBLEM OR FUNCTION - AIRDIF is a two-dimensional atmospheric radiation diffusion code designed to calculate neutron and gamma doses in the environment of a nuclear explosion. It calculates radiation fluxes in one-dimensional homogeneous air, or two-dimensional variable density air. The results are limited by the assumptions inherent in diffusion theory: the region of interest must be large compared to the radiation mean free path, the spatial flux gradients must not be steep, flux varies linearly with the cosine of the direction angle.
The code requires as input data neutron and gamma source spectra, coupled neutron-gamma multigroup cross sections, and, for two- dimensional problems, a set of mass integral scaling (MIS) coefficients. These latter are calculated from an AIRDIF output flux file for a one-dimensional problem by the auxiliary program MISFIT, using a least squares fitting technique to Murphy's radiation transmission equation. MISFIT can also be used to calculate one- dimensional MIS doses.
The MIS coefficients and doses can be input to AIRDIF, in two- dimensional mode to calculate 2-D fluxes, doses and K-factors (the ratio of 2-D to 1-D dose). Alternatively the 2-D doses and K-factors may be computed using the output 2-D flux file of a previous AIRDIF run using the auxiliary program DOSCOMP.


4. METHOD OF SOLUTION - Uncollided particle flux is determined from an analytic expression describing exponential attenuation with distance. Diffusion theory is used for the flux, using uncollided flux as a source term. A central collided differencing technique is used to reduce the diffusion equation to a matrix equation, which is solved by the Successive Line Overrelaxation (SLOR) method. Total flux is calculated as the sum of collided and uncollided components.
To maintain a mesh interval which has the same relationship to mean free path at all heights, an expanding non-orthogonal coordinate system is used. In homogeneous air this system reduces to cylindrical coordinates.


5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM - 


6. TYPICAL RUNNING TIME - Execution times are dependent on the number of mesh points and energy groups, and the rate of convergence. Typically a 1500 mesh point 58 group problem requires 60 seconds CPU time on CDC 7600. Execution on a CDC 6600 takes four to five times longer.

CCC-0360/01:

 NEA-DB executed the test case on CDC CYBER 740 in 490 seconds of CPU time. 


7. UNUSUAL FEATURES OF THE PROGRAM - 


8. RELATED AND AUXILIARY PROGRAMS - The two auxiliary programs MISFIT and DOSCOMP are mentioned in section 3 above.


9. STATUS
CCC-0360/01: 24-MAY-1985 Tested at NEADB


10. REFERENCES  - 
CCC-0360/01:
 -  R. A. Shulstad, E. L. Wolf:
    AIRDIF: A Two-Dimensional Atmospheric Radiation
            Diffusion Computer Code.
    AFWL-TR-77-29 (June 1977)


11. MACHINE REQUIREMENTS - Adequate storage for a 1500 mesh point, 61 energy group problem is provided by 200k octal words on a CDC 6600. In addition 15 external storage devices are required.

CCC-0360/01:

The test case included in the package runs on CDC CYBER740 in 331,100 words (octal).


12. PROGRAMMING LANGUAGE(S) USED -
CCC-0360/01: FORTRAN-IV 


13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED - 
NOS 1.4-531 (CDC CYBER 740). 


14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS - 


15. NAME AND ESTABLISHMENT OF AUTHOR - 
R.A. Shulstad, E.L. Wolf 
Air Force Weapons Laboratory 
Air Force Systems Command 
Kirtland Air Base 
New Mexico 87117, U.S.A. 


16. MATERIAL AVAILABLE -
CCC-0360/01:
CCC0360_01.003    INFORMATION FILE                                   51 records
CCC0360_01.004    AIRDIF SOURCE PROGRAM (CARD IMAGES)              2501 records
CCC0360_01.005    JCL TO RUN TEST CASE                               17 records
CCC0360_01.006    AIRDIF TEST CASE INPUT DATA (CARD IMAGES)         238 records
CCC0360_01.007    AIRDIF TEST CASE PRINTED OUTPUT                  2272 records
CCC0360_01.008    MISFIT SOURCE PROGRAM (CARD IMAGES)               307 records
CCC0360_01.009    DOSCOMP SOURCE PROGRAM (CARD IMAGES)             1023 records


17. CATEGORIES  - 

- G. Radiological Safety, Hazard and Accident Analysis
- R. Environmental and Earth Sciences


Keywords: DIFFUSION, DIFFUSION EQUATIONS, DOSES, EARTH ATMOSPHERE, FLUX DISTRIBUTION, GAMMA RADIATION, NEUTRONS, NUCLEAR EXPLOSIONS, ONE-DIMENSIONAL, RADIONUCLIDE MIGRATION, TWO-DIMENSIONAL

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