CCC-0520: DCTDOS, Neutron and Gamma Penetration in Composite Duct System

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CCC-0520 DCTDOS. (Abstract last modified 16-OCT-1990)

DCTDOS, Neutron and Gamma Penetration in Composite Duct System

Abstract Table of Contents:

1. NAME OR DESIGNATION OF PROGRAM - DCTDOS.

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

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Explanation of the status codes.

Program-name Package-ID Status DCTDOS CCC-0520/01 Tested

Machines used: Package-ID Orig.Computer Test Computer CCC-0520/01 IBM PC IBM PC

3. DESCRIPTION OF PROGRAM OR FUNCTION - Estimates are made of neutron and gamma-ray fluence rate (flux density), dose, and spectral features due to penetration through a series of duct segments -
straight sections and bends - in arbitrary combinations; and the resulting composite can include computations for a room at the end, if there is one. This method was developed for the rapid estimates that are needed for analysis of protection problems against nuclear weapons, but the concepts are more generally applicable.

4. METHOD OF SOLUTION - The method, called "orders of reflection", involves the following steps: (1) The penetration of the radiation (neutrons or gamma rays) through single straight ducts of various dimensions is first calculated in a one-velocity treatment, assuming an albedo with an angular dependence given by Chandrasekhar's theory, and assuming isotropic scattering. This penetration probability is calculated for the case of 0, 1, 2, ...n reflections from walls; (2) An estimate of the energy and angular characteristics of the radiation transmitted after 0, 1, 2, ..., n
reflections is then made by using the results of a Monte Carlo calculation in which the energy and angular characteristics of the multiply-reflected radiation is computed in a space-independent treatment; (3) The results of calculations (1) and (2) are combined to obtain a transfer function which relates the intensities, direction, and energy characteristics of the radiations entering and leaving a single straight duct or duct segment.
Using the output of one such calculation as the input for the next, the transmissions of the radiation through a sequence of ducts can readily be calculated for any spatial configuration of successive duct legs. The approximations made in the orders-of- reflection method are particularly applicable to neutrons. However, the method, with some adaptation, has also been found to be applicable to gamma rays.
An extensive data base of neutron and gamma albedo data has been incorporated into the system which allows very rapid calculations of radiation penetration of complex duct configurations. Trial calculations have indicated very good agreement with published Monte Carlo calculations. The method may also be applied to shielding problems pertaining to medical radiation sources and accelerators, but the code has not been tested for these applications.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM - The neutron calculations use 20 reflections from the duct walls while the gamma-ray calculations use 9 (maximum values of "n" mentioned above).

6. TYPICAL RUNNING TIME - Execution of the sample problems takes a few minutes on an IBM PC.

7. UNUSUAL FEATURES OF THE PROGRAM -

8. RELATED AND AUXILIARY PROGRAMS -

9. STATUS
CCC-0520/01: 16-OCT-1990 Tested at NEADB

10. REFERENCES  -
CCC-0520/01:
- L.V. Spencer:
  DCTDOS: Neutron and Gamma Penetration in Composite Duct Systems.
  NSBIR 87-3534, National Bureau of Standards  (February 1987)

11. MACHINE REQUIREMENTS - The minimum hardware requirements for DCTDOS: an IBM PC or compatible with 2 floppy disk drives and 640K Random Access Memory. An 8087 math coprocessor is desirable.

CCC-0520/01:

Main storage requirements on an IBM PC/AT are about 190 kBytes.

12. PROGRAMMING LANGUAGE(S) USED -
CCC-0520/01: FORTRAN-77

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED - The Microsoft Version 3.31 was used to compile the program under PC/DOS 3.1. The Microsoft linker LINK.EXE wa used to create two executable files. One (160K bytes) requires the 8087 coprocessor, and the other (227K bytes) does not. The executable files are included in the package.

CCC-0520/01:

The program ran on the PC/AT under MSDOS version 3.20 with the Microsoft FORTRAN version 5.0 compiler.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS -

15. NAME AND ESTABLISHMENT OF AUTHORS -
      Contributed by:  Radiation Shielding Information Center
                       Oak Ridge National Laboratory
                       Oak Ridge, Tennessee, U. S. A.
      Developed by:    National Bureau of Standards
                       Gaithersburg, Maryland, U. S. A.

17. CATEGORIES -

- J. Gamma Heating and Shield Design

Keywords: DUCTS, GAMMA RADIATION, NEUTRON FLUX, SHIELDING