CCC-0341 AIRSCAT.

1. NAME OR DESIGNATION OF PROGRAM:  AIRSCAT.
Calculation of dose rate for gamma rays scattered in air.

3. DESCRIPTION OF PROBLEM OR FUNCTION

Present methods of solution to determine dose rates from air-scattered gamma rays utilize the concept of multiple scattering. These methods compute many possible  scattering paths to derive the desired value. One of the most used techniques is the Monte Carlo, which is quite time consuming and costly in regard to computer usage and memory size requirements. The AIRSCAT program was developed as a calculation scheme for air-scat-  tered gamma rays using the single-scattering approximation with no exponential attenuation or buildup. The program has been useful for  preliminary design work and estimation when dealing with unshielded  detectors. The main advantage of this type of calculation is: closed form solutions, small computer memory, large time saving and lower cost as compared to the Monte Carlo methods.

4. METHOD OF SOLUTION

The AIRSCAT program uses the once scattered component of Compton scattering to determine individual dose rate contributions at various scatter points within the scattering region. These scattering points are defined by a nonuniform scatte-  ing grid, which takes advantage of the fact that the gamma ray pho-  ton energy decreases as a function of the scattering angle and dis-  tance from the source, thus the scattering region is biased for the  most important scatter points. Once the contribution has been esta-  blished for each individual scatter point, a total dose rate is de-  rived by integration over the entire scattering region.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The results of the AIRSCAT program, using the single scattering approximation, with no exponential attenuation or buildup, are useful for preliminary design work and estimation. The results show that the simple appro-  ximation is adequate for unshielded detectors. If the detector is shielded in any way, however, these results would not be valid, since energy and angular distribution at the shield are important.

6. TYPICAL RUNNING TIME:

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS:

10. REFERENCES:

- A Thesis by M.C. Guile:
  AIRSCAT - Calculation of Dose Rate for Gamma-rays Scattered in Air
  (April 1978).
- A Thesis by M.C. Guile:
  AIRSCAT - Calculation of Dose Rate for Gamma-rays Scattered in Air
  (April 1978).

11. MACHINE REQUIREMENTS:

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

Contributed by:
Worchester Politechnic Institute
Worchester, Massachusetts
received from RSIC

source program   mag tapesource program   mag tape                  SRCTP
report                   RSIC report (April 1978)                   REPPT

File name	File description	Records
CCC0341_02.002	AIRSCAT INFORMATION	18
CCC0341_02.003	AIRSCAT, SOURCE PROGRAM (FORTRAN-4)	188
CCC0341_02.004	AIRSCAT, JCL FOR TEST CASE 1	5
CCC0341_02.005	AIRSCAT, INPUT FOR TEST CASE 1	4
CCC0341_02.006	AIRSCAT, OUTPUT OF TEST CASE 1	89