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CCC-0110 AIRTRANS.

AIRTRANS, Time-Dependent, Energy Dependent 3-D Neutron Transport, Gamma Transport in Air by Monte-Carlo

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1. NAME OR DESIGNATION OF PROGRAM:  AIRTRANS.
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2. COMPUTERS
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Program name Package id Status Status date
AIRTRANS CCC-0110/01 Tested 01-MAR-1979

Machines used:

Package ID Orig. computer Test computer
CCC-0110/01 IBM 360 series IBM 360 series
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3. NATURE OF PHYSICAL PROBLEM SOLVED

The function of the AIRTRANS system is to calculate by Monte Carlo methods the radiation field produced by neutron and/or gamma-ray sources which are located in the atmosphere. The radiation field is expressed as the time - and energy-dependent flux at a maximum of 50 point detectors in the atmosphere. The system calculates uncollided fluxes analytically and collided fluxes by the "once-more collided" flux-at-a-point technique. Energy-dependent response functions can be applied to the fluxes to obtain desired flux functionals, such as doses, at the detector point. AIRTRANS also can be employed to generate sources of secondary gamma radiation.
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4. METHOD OF SOLUTION

Neutron interactions treated in the calculational scheme include elastic (isotropic and anisotropic) scattering, inelastic (discrete level and continuum) scattering, and absorption. Charged particle reactions, e.g, (n,p) are treated as absorptions. A built-in kernel option can be employed to take neutrons from the 150 kev to thermal energy, thus eliminating the need for particle tracking in this energy range. Another option used in conjunction with the neutron transport problem creates an "interaction tape" which describes all the collision events that can lead to the production of secondary gamma-rays. This interaction tape subsequently can be used to generate a source of secondary gamma rays.
The gamma-ray interactions considered include Compton scattering, pair production, and the photoelectric effect; the latter two processes are treated as absorption events.
Incorporated in the system is an option to use a simple importance sampling technique for detectors that are many mean free paths from  the source. In essence, particles which fly far from the source are  split into fragments, the degree of fragmentation being proportional to the penetration distance from the source. Each fragment is tracked separately, thus increasing the percentage of computer time  spent following particles at the deep penetrations. Each fragment is assigned a "weight" which is inversely proportional to the degree of fragmentation suffered by original source particle.
All estimates of flux contributions by such a fragment are then multiplied by its assigned weight.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

ND = number of detectors less than or equal to 50*
NE = number of energy bins less than or equal to 50*
NT = number of time bins less than or equal to 50*
*subject to 3 ND x NE x NT + 2 NT x NE less than or equal to 1500- ited, where ited = 1464 for neutrons and 1054 for gammas.
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6. TYPICAL RUNNING TIME

Estimated running time of the sample problem on the CDC 1604: AIRSCA, 3 minutes; DATORG, 3 minutes. Sample problem does not use VANGEN or ASP. Typical running time on the UNIVAC 1108 varies from 1/4 to 1/2 sec/history/detector.
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7. UNUSUAL FEATURES: UNUSUAL FEATURES OF THE PROGRAM
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8. RELATED AND AUXILIARY PROGRAMS

DATORG: organized data tape generator.
VANGEN: external source generator.
ASP: anisotropic secondary particle generator.
AIRSCA: calculates time-energy dependent fluxes at point in atmosphere.
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9. STATUS
Package ID Status date Status
CCC-0110/01 01-MAR-1979 Tested at NEADB
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10. REFERENCES

- G.L. Case:
  Utilization Manual AIRTRANS
  LMSC-5234 (February 1968).
CCC-0110/01, included references:
- M.O. Cohen:
  "AIRTRANS - A Time-Dependent Monte Carlo System for Radiation
   Transport in a Variable Density Atmosphere and the Ground"
  UNC-5179 (June 1967).
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11. MACHINE REQUIREMENTS

The programme was originally designed for the  CDC 1604 using standard I-O and a maximum of 4 tape units. It was converted for use on the UNIVAC 1108 by Lockheed Missile and Space Company.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
CCC-0110/01 FORTRAN-IV
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13. SOFTWARE REQUIREMENTS: OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS
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15. NAME AND ESTABLISHMENT OF AUTHOR

     United Nuclear Corporation
     Elmsford, New York, U. S. A.

     Lockheed Missile and Space Company                                             Sunnyvale, California, U. S. A.
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16. MATERIAL AVAILABLE
CCC-0110/01
File name File description Records
CCC0110_01.001 INFORMATION 6
CCC0110_01.002 81 PTS. NEUTRON CROSS SECTIONS (BCD) 8307
CCC0110_01.003 81 PTS. GAMMA CROSS SECTIONS (BCD) 2642
CCC0110_01.004 DATORG --- SOURCE PROGRAM (F4,EBCDIC) 365
CCC0110_01.005 DATORG1 --- DD CARDS 8
CCC0110_01.006 DATORG1 --- SAMPLE PROB. INPUT DATA 238
CCC0110_01.007 DATORG1 --- SAMPLE PROB. PRINTED OUTPUT 536
CCC0110_01.008 DATORG2 --- DD CARDS 8
CCC0110_01.009 DATORG2 --- SAMPLE PROB. INPUT DATA 238
CCC0110_01.010 DATORG2 --- SAMPLE PROB. PRINTED OUTPUT 415
CCC0110_01.011 VANGEN --- SOURCE PROGRAM (F4,EBCDIC) 365
CCC0110_01.012 VANGEN --- DD CARDS 5
CCC0110_01.013 VANGEN --- SAMPLE PROB. INPUT DATA 6
CCC0110_01.014 VANGEN --- SAMPLE PROB. PRINTED OUTPUT 608
CCC0110_01.015 ASP --- SOURCE PROGRAM (F4,EBCDIC) 615
CCC0110_01.016 ASP --- DD CARDS 8
CCC0110_01.017 ASP --- SAMPLE PROB. INPUT DATA 8
CCC0110_01.018 ASP --- SAMPLE PROB. PRINTED OUTPUT 1493
CCC0110_01.019 AIRSCA --- SOURCE PROGRAM (F4,EBCDIC) 2407
CCC0110_01.020 AIRSCA1 --- DD CARDS 11
CCC0110_01.021 AIRSCA1 --- SAMPLE PROB. INPUT DATA 17
CCC0110_01.022 AIRSCA1 --- SAMPLE PROB. PRINTED OUTPUT 1196
CCC0110_01.023 AIRSCA2 --- DD CARDS 10
CCC0110_01.024 AIRSCA2 --- SAMPLE PROB. INPUT DATA 17
CCC0110_01.025 AIRSCA2 --- SAMPLE PROB. PRINTED OUTPUT 294
CCC0110_01.026 AIRSCA3 --- DD CARDS 10
CCC0110_01.027 AIRSCA3 --- SAMPLE PROB. INPUT DATA 17
CCC0110_01.028 AIRSCA3 --- SAMPLE PROB. PRINTED OUTPUT 291
CCC0110_01.029 ASP --- SOURCE PROGRAM (F4) 330
CCC0110_01.030 AIRTRANS -- SOURCE PROGRAM (F4) 4082
CCC0110_01.031 AIR DENSITY TABLE (BCD) 233
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis

Keywords: Monte Carlo method, absorption, collisions, doses, elastic scattering, gamma radiation, inelastic scattering, neutron transport theory, radiation effects, secondary emission, time dependence.